Building Control Guidance For Domestic loft conversion

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BUILDING CONTROL
GUIDANCE
FOR
DOMESTIC LOFT CONVERSIONS
OCTOBER 2010 EDITION 4

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Introduction
This document intends to provide education and guidance on how some of the technical design
and construction requirements of the Building Regulations 2010 can be achieved and met for
loft conversions to dwellings up to two storeys in height and within 4.5m of ground level and
additional guidance is given for three storeys in height which has a floor 4.5m above ground
level. For loft conversions of four storeys or more with more than one floor above 4.5m please
contact building control for advice.
In all cases the design and construction of the proposed works is the responsibility of the
designer, applicant and contractor and should be carried out to the relevant submitted and
approved design. For further information reference should be made to the relevant Approved
Document or standard as well as consulting a suitably qualified and experienced construction
professional.
The Approved Documents listed below are available to purchase from The Stationary Office
(TSO) on line at www.tsoshop.co.uk or telephone: 0870 600 5522.
However, the Building Regulation requirements may be satisfied in other ways or non-standard
ways by calculations or test details from a manufacturer or an approved 3rd party method of
certification such as BBA (British Board of Agreement) Certificate.
This document can be made available on a range of other formats if required. For further
information please contact us on 01594 810000.
Approved Documents and sections they cover;
A: Structure (2004 edition) including TRADA span tables for solid timber members in floors,
ceilings and roofs for dwellings (2nd edition 2008)*;
B1: Fire safety in dwelling houses (2006 edition);
C: Site preparation and resistance to contaminants & moisture (2004 edition);
D: Toxic substances (1992 with 2002 amendments);
E: Resistance to the passage of sound (2003 with 2004 amendments);
F: Ventilation (2010 edition);
G: Sanitation, hot water safety and water efficiency (2010 edition);
H: Drainage and waste disposal (2002 edition);
J: Combustion appliances & fuel storage systems (2010 edition);
K: Protection from falling, collision and impact (1998 with 2002 amendments);
L1B: Conservation of fuel and power in existing dwellings (2010 edition);
N: Glazing – Safety in relation to impact, opening & cleaning (1998 with 2000 amendments);
P: Electrical safety (2006 edition);
Regulation 7 Materials and workmanship (1992 with 2000 amendments).
Other guidance documents available: New Dwellings, New extensions
Commercial/industrial buildings & Fire Safety for Conversion of buildings into Holiday Lets,
Guest Houses & Supervised Groups with Learning Difficulties.
Important note: Typical section details have been provided in these guidance notes for the
more common construction methods used in dwellings. These details are suggested methods of
construction and are for guidance only. You are advised to contact a suitably qualified and
experienced property professional for details and specifications for the most suitable form and
method of construction for your project.

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CONTENTS PAGE NUMBER
INTRODUCTION 2
1.0 CONVERTING AN EXISTING LOFT SPACE 6
2.0 ENGAGING A PROPERTY PROFESSIONAL
3.0 OBTAINING BUILDING REGULATIONS APPROVAL
3.1 full plans application
3.2 building notice application 7
4.0 EXEMPT BUILDINGS AND WORK
5.0 COMPETENT PERSON SCHEME
6.0 PLANNING PERMISSION, LISTED BUILDING & CONSERVATION AREA CONSENTS 8
7.0 THE PARTY WALL ACT 1996
8.0 CONSTRUCTION (DESIGN AND MANAGEMENT) REGULATIONS 2007 (CDM)
9.0 ASSESSING THE FEASIBILITY OF YOUR LOFT CONVERSION 9
10.0 GENERAL TECHNICAL & PRACTICAL GUIDANCE FOR LOFT CONVERSIONS 10
A1: PREPARATION, PROTECTION, ACCESS & DEMOLITION
A2: INSPECTION OF THE EXISTING ROOF & STRUCTURE
A3: ALTERATION, MODIFICATION & STRENGTHENING OF THE EXISTING ROOF/STRUCTURE
Diagram 1: Typical plan layout of a loft conversion with dormer pitched roof 11
Diagram 2: Typical section through a loft conversion with dormer pitched roof 12
Diagram 3: Typical section through a loft conversion with dormer flat roof
A4: NEW PITCHED ROOFS 13
Pitched roof coverings
Pitched roof structure
Roof trusses (including attic & girder trusses)
Cut roof construction
Table 1: Spans for Common Domestic Timber Rafter Sizes at 400mm spacing 14
Table 2: Spans for Common Domestic Timber Ceiling Joist Sizes at 400mm spacing
Table 3: Spans for Common Domestic Timber Purlin Sizes
Table 4: Permissible Clear Spans for Common Ceiling Binders Sizes 15
Diagram 4: Typical section through a pitched roof
Roof restraint
Roof insulation 16
Table 5: Insulation laid horizontally between and over ceiling joists
Table 6: Insulation fixed between/under rafters
Table 7: Insulation fixed between/over rafters
Diagram 5: Typical roof valley detail 17
Diagram 6: Typical section through a dormer roof
Roof ventilation 18
A5: FLAT ROOF CONSTRUCTION
Diagram 7: Typical section through a flat (cold) roof 19
Table 8: Spans for Common Flat Roof Joist Sizes
Table 9: Insulation Fixed Between/Under Flat Roof Joists 20
Table 10: Insulation Fixed above Flat Roof Joists
Valleys and lead work
Lofts hatches, doors & Light wells to roof spaces
A6: NEW EXTERNAL WALLS 21
Cavity walls
Table11: Insulation requirements for external cavity walls
External timber framed walls with render finish 22
Diagram 8: Typical section through external timber framed walls with render finish
External timber framed walls with cladding finish
Diagram 9: Typical section through external timber framed walls with cladding finish 23
Wall abutments
Lintels & weep holes
Structural columns/beams etc
Expansion joints
Strapping and restraint
Cavity closers
A7: INTERNAL LOAD BEARING WALLS 24
Internal load bearing timber stud walls
Diagram 10: Typical section through internal load bearing timber stud wall supporting
roof loads
Table 12 : Insulation requirements to exposed timber framed walls
Internal load bearing masonry partitions
A8: INTERNAL NON LOAD BEARING PARTITIONS 25
Internal masonry non-load bearing partitions
Internal timber studwork non-load bearing partitions

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A9: UPGRADING EXISTING EXTERNAL WALLS 26
Diagram 11: Typical plan layout of upgrading existing walls in loft conversion
Table 13: Insulation requirements for upgrading existing external walls
A10: SEPARATING (PARTY) WALLS & FLOORS BETWEEN DWELLINGS 27
Masonry party walls separating dwellings
Timber frame party walls separating buildings
Upgrading sound insulation of existing separating walls
Party floors separating buildings
Sound testing requirements
A11: ADDITIONAL PROVISIONS FOR 3 STOREY BUILDINGS/EXTENSIONS 28
Compressive strength of masonry units
A12: INTERMEDIATE UPPER FLOOR(S)
Diagram 12: Typical section through a loft floor
Diagram 13: Typical section through an upper floor 29
Table 14: Spans for Common Domestic Floor Joist Sizes
Table 15: Spans for Common Trimmer Joist supporting Trimmed Joists
Table 16: Spans for Common Trimming Joist supporting Trimmer Joist
Sound insulation to floors within the dwelling 30
SVP pipe boxing
Exposed intermediate upper floors
Table 17: Insulation requirements to exposed intermediate floors
PART B: FIRE SAFETY & MEANS OF ESCAPE 31
MEANS OF ESCAPE FROM SINGLE STOREY DWELLING WITH NEW SECOND STOREY
MEANS OF ESCAPE FROM TWO STOREY DWELLINGS WITH NEW THIRD STOREY 32
Option 1: Protected stairway
Option 2: Protected stairway with alternative exits at ground floor level 33
Option 3: Fire separated 3
rd
storey with alternative external/internal fire exit 34
Option 4: Residential sprinkler systems for means of escape 35
Fire doors
Smoke alarms
Fire resistance to new storey floor 36
Permitted building openings in relation to a boundary:
Openings within 1.0m of a boundary
Openings more than 1.0m from a boundary
Table 18: Permitted unprotected areas in relation to a relevant boundary
Fire resistance to elements of structure etc
Table 19: Fire resistance to common elements of structure etc
Surface spread of flame: wall & ceiling linings 37
Table 20: Surface spread of flame: Classification of wall & ceiling linings
PART C: SITE PREPARATION AND RESISTANCE TO CONTAMINANTS & MOISTURE 38
Horizontal damp proof courses & trays (dpc’s)
Vertical damp proof courses & trays etc (dpc’s)
PART D: CAVITY WALL FILLING WITH INSULATION BY SPECIALISTS
PART E: RESISTANCE TO THE PASSAGE OF SOUND
New Internal walls & floors in loft conversion
New/existing party walls and floors in loft conversion
PART F: VENTILATION 39
Purge (natural) ventilation
Mechanical extract ventilation & fresh air inlets for rooms without purge ventilation
Background ventilation
Mechanical extract ventilation rates
General requirements for mechanical extract ventilation
PART G: SANITATION, HOT WATER SAFETY AND WATER EFFICIENCY 40
PART H: DRAINAGE AND WASTE DISPOSAL 41
H1: FOUL WATER DRAINAGE
Foul, rain & storm water drainage systems
Waste pipes
H2: SEPTIC TANKS, SEWAGE TREATMENT SYSTEMS & CESSPOOLS 42
Existing septic tank & effluent drainage
Non mains foul drainage waste water treatment systems
Septic tanks
Sewage treatment systems 43
Treatment of sewage from septic tanks & sewage treatment systems
Drainage fields
Drainage mounds
Wetlands/reed beds 44
Percolation test method to calculate area of drainage field for septic tanks
or sewage treatment systems.
Diagram 14: Typical section through a septic tank/sewage treatment system drainage field 45
Diagram 15 : Typical drainage field plan layout (not to scale)

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H3: RAINWATER DRAINAGE AND HARVESTING 46
Rainwater gutters and down pipes
Table 21: Gutter sizes & pipe outlet sizes for drainage of roof areas
Rainwater/ grey water harvesting storage tanks & systems
Surface water drainage around the building
PART J: COMBUSTION APPLIANCES & FUEL STORAGE SYSTEMS 47
SPACE & HOT WATER HEAT PRODUCING APPLIANCES IN GENERAL
SOLID FUEL APPLIANCES UP TO 50KW RATED OUTPUT
Construction of open fire place with recess & hearth
Free standing stove with hearth
Air supply (ventilation) to solid fuel appliances
Table 22: Air supply (ventilation) to solid fuel appliances 48
Carbon monoxide alarms
Table 23: Sizes of flues in chimneys
Construction of masonry chimneys 49
Construction of factory made flue block chimneys
Construction of factory made metal chimneys
Configuration of flues serving open flue appliances
Inspection & cleaning openings in flues
Interaction of mechanical extract vents & opened flue solid fuel appliances
Chimney heights 50
Repair/relining of existing flues
Notice plates for hearths & flues
APPLIANCES OTHER THAN SOLID FUEL
Interaction of mechanical extract vents & opened flue combustion appliances
Gas appliances
Oil appliances
Gas heating appliances up to 70kw
Oil heating appliances up to 45kW 51
Renewable energy Installations
PROVISION OF INFORMATION- COMMISSIONING CERTIFICATES (TESTING)
FUEL STORAGE TANKS
LPG tanks and cylinders up to 1.1 tonnes
Oil tanks up to 3500 litres
PART K: PROTECTION FROM FALLING, COLLISION AND IMPACT 52
STAIRS, LANDINGS AND CHANGES IN LEVEL OF 600MM OR MORE (INCLUDING EXTERNAL STEPS)
Diagram 16: Measuring rise & goings
Diagram 17: Typical internal stair case & guarding construction details 53
GUARDING TO EXTERNAL STEPPED ACCESS, BALCONIES, FLAT ROOFS
& LOW LEVEL WINDOW OPENINGS
PART L: CONSERVATION OF FUEL AND POWER IN EXISTING DWELLINGS 54
LISTED BUILDINGS, CONSERVATION AREAS & ANCIENT MONUMENTS
AREAS OF EXTERNAL WINDOWS, ROOF WINDOWS & DOORS
NEW THERMAL ELEMENTS
External glazing
Table 24: U Values for new external windows & doors including roof windows
Closing around window & door openings
Sealing Measures
External Walls, roofs, floors & swimming pool basin 55
Table 25: U Values for new external walls, roofs, floors & swimming pool basin
RENOVATION/UPGRADING OF EXISTING THERMAL ELEMENTS
Table 26: Renovation/upgrading of existing thermal elements
Payback report
ENERGY EFFICIENT LIGHTING 56
Fixed internal lighting
Fixed external lighting
CONSEQUENTIAL IMPROVEMENTS
COMMISSIONING OF FIXED BUILDING SERVICES
PROVIDING INFORMATION -BUILDING LOG BOOK
PART N: SAFETY GLAZING, OPENING & CLEANING 57
Safety glass and glazing
Diagram 18: Glazing in windows, partitions, doors, side panels/screens & walls
PART P: ELECTRICAL SAFETY 58
Electrical Installations
EXTERNAL WORKS- PATHS, DRIVES, PATIO & GARDENS 59
MATERIALS AND WORKMANSHIP 60
ADDITIONAL BUILDING CONTROL SERVICES WE CAN PROVIDE
GLOUCESTERSHIRE BUILDING CONTROL DEPARTMENTS CONTACT DETAILS 61
USEFUL NUMBERS OF OTHER AGENCIES OR COMPANIES

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1.0 Converting an existing loft space
Converting an existing loft space can be an easy and cost effective way of increasing living
accommodation in most houses. This guide to loft conversions will provide useful guidance on
how some of the technical design and construction requirements of the Building Regulations
can be achieved where the loft space of an existing one or two storey dwelling is being
converted into habitable accommodation to form an additional storey to the dwelling. Where the
house has three or more storeys before the loft is converted -please contact building control for
further guidance.
2.0 Engaging a property professional
This type of work can be complex and unless you are experienced in construction you will need
to get some professional advice from the following:
1. Appointing a suitably qualified and experienced property professional who will prepare
drawings and designs for your proposal, obtain the necessary approvals and if required
they will also help you to find a suitable builder and manage the project for you.
2. Appointing a specialist company who can offer a one stop shop for this type of work, they
can prepare drawings and designs for your proposal, obtain the necessary approvals and
carry out all the necessary construction works to complete the project.
3. Using an experienced builder.
3.0 Obtaining Building Regulations approval
The building owner or agent must make a building regulations application & pay a fee for the
proposed works. All work must comply with the 2010 Building Regulations and the technical
design and constructional requirements of the current Approved Documents A to P and
Regulation - 7 Materials and Workmanship.
The person carrying out the building works is to liaise with and meet the requirements of the LA
Building Control/Certifying Body, giving required notices of stages of works as required by the
Building Regulations including:
 Foundation excavations before any concrete is laid
 Over site covering to ground floors before any concrete is laid
 Foul & surface water drainage before any pipes are covered over
 Structural timbers (upper storey floor joists/beams and roof structure before any
coverings are fixed
 Completion of building-prior to occupation
There are two methods of making a Building Regulations application as follows:
3.1 Full Plans application
This is often thought of as the traditional way of applying for Building Regulations
Approval. The building designer will draw up detailed plans and supporting information
for the proposed scheme and will send them to us together with a completed application
form and the necessary fee which are available to down load from our web site at:
www.fdean.gov.uk. We will then check the details and following any necessary
consultations and liaisons with the building designer a Building Regulations Approval will
be issued.
Work can start any time after the application has been received although it is wise to wait
until the scheme has had its initial check under the Building Regulations, this usually
takes between two and three weeks.

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Our team of surveyors will liaise with your builder and inspect the work as it progresses
on site. When the project is satisfactorily completed a Building Regulations Completion
Certificate will be issued showing that the project has been independently inspected and
that it complied with the Building Regulations.
3.2 Building Notice application
This system is best suited to minor domestic work carried out by a competent builder.
Under this scheme no formal Approval of plans is issued and work is approved on site as
it progresses.
To use the Building Notice process you or your agent will need to submit a completed
Building Notice application form together with a site location plan and the required fee.
The application forms are available to down load from our web site at:
www.fdean.gov.uk. Work can commence 48 hours after the notice has been received.
When work commences one of our surveyors will meet with your builder to discuss your
intentions, to agree how the work should be carried out, agree when the work will need to
be inspected and to establish whether any further information will be required.
When the project is satisfactorily completed a Building Regulations Completion
Certificate will be issued showing that the project has been independently inspected and
that it complied with the Building Regulations.
4.0 Exempt buildings and work
Green Houses & agricultural buildings: Buildings used for agriculture or keeping of animals
providing no part is used as as a dwelling and is more than 1.5 times its height from a building
containing sleeping accommodation
Temporary buildings: Buildings erected for less than 28 days
Ancillary buildings: Buildings used in connection with the sale of buildings or plots on that site,
or in connection with a building project or mine/quarry and contains no sleeping
accommodation.
Small detached buildings (garages, workshops or sheds): A detached single storey building
with less than 30m2
internal floor area, with no sleeping accommodation. If constructed
substantially of combustible materials it must be positioned at least one metre from the
boundary of its cartilage. Other detached buildings with less than 15m2
internal floor area, with
no sleeping accommodation. (no boundary restrictions if constructed of combustible materials)
Conservatory, porch, covered yard/way & carports: A detached single storey building with
less than 30m2
internal floor area, fitted with safety glass in critical locations in compliance with
ADN. Existing walls, doors & windows of the building separating the conservatory or porch is to
be retained or, if removed are replaced with elements that meet the energy efficiency
requirements of ADL1B. The heating system of the dwelling must not be extended into the
conservatory or porch. Carports must be open on two sides.
5.0 Competent Person Scheme
Certain works can be carried out by an installer who is registered with a Competent
Persons Scheme and will not require building regulations approval. For a list of all
scheme members go to www.competentperson.co.uk

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6.0 Planning Permission, listed building & conservation area consents
Planning permission, listed building/conservation area consents may be required for your
proposed development and no works should be commenced until approval has been
given by the planning department.
If the requirements of the building regulations will unacceptably alter the character or
appearance of a historic/listed building/ancient monument or building within
a conservation area, then the requirements may be exempt or improved to what is
reasonably practical or acceptable and would not increase the risk of deterioration of the
building fabric or fittings in consultation with the local planning authorities conservation
officer. For any further information, please contact the FODDC duty planning officer on
01594 810000.
7.0 The Party Wall Act 1996
If the project affects a party wall, you may be required to give your neighbor the
required notice under the Party Wall Act.
Two months notice in writing is to be given to adjoining owner(s) for the following works to an
existing Party Wall:
 Support of beam
 Insert DPC through wall
 Raise wall or cut off projections
 Demolition and rebuilding
 Underpinning
 Insert lead flashings
 Excavations within 3 meters of an existing structure where the new foundations will go
deeper than adjoining foundations, or within 6 meters of an existing structure where the
new foundations are within a 45 degree line of the adjoining foundations.
In the event of a disagreement, a Party Wall Surveyor may be required to resolve the dispute
under the terms of the Party Wall Act. Copies of the Party Wall Act can be obtained from the
Council Offices or www.communities.gov.uk
8.0 Construction (Design and Management) Regulations 2007 (CDM)
The Construction (Design and Management) Regulations 2007 apply to every
construction project. If you are about to undertake construction work, which could include
alterations, extensions, routine maintenance, new build or demolitions, then you need to
know to what extent these Regulations will apply to you and whether you are a duty
holder under these Regulations.
With non-domestic* projects expected to last longer than 30 days, or more than 500 man
hours, you will require the assistance of an advisor called a CDM Co-ordinator, who
should be appointed at the earliest opportunity, before detailed design work is complete.
If you are a Client thinking of commissioning work, a Designer appointed to work on a
project, or a builder/developer about to undertake work, you should be aware of your
responsibilities or duties under CDM 2007.
*Non-domestic Clients are people who commission building works related to a
trade or business, whether for profit or not. This work can be carried out on a
domestic property; it is the type of Client that matters, not the type of property.

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9.0 Assessing the feasibility of your loft conversion
Before commencing a loft conversion it is important to assess the feasibility of the project. This
will involve inspection of the existing loft & dwelling to assess the following:
Roof structure & shape- The overall form, construction and profile of the roof will have a major
bearing on the whether the roof is suitable for conversion to a usable space. Traditional cut
timber pitched roofs with gable ends walls (cavity walls or solid walls at least 250mm thick) and
horizontal ridges are generally easier to convert and can normally support structural beams than
hipped roofs or roofs with intersecting pitches and valleys which may require more complicated
structural designs.
Trussed rafter roofs constructed using a series of complex trusses should only be altered,
modified and converted in compliance with details and calculations carried out by a suitable
qualified and experience property professional. No trussed rafter should ever be cut or modified
in any way until a new supporting structure is in place which has been designed by a suitably
qualified and experienced specialist designer. Further information for loft conversions with
trussed rafter roofs can be obtained from TRADA at: www.tra.org.uk
All existing timbers should be in a sound condition, any defective timber is to be replaced with
new in compliance with details and calculations carried out by a suitable qualified and
experience property professional. Existing timbers are to be inspected and where necessary
treated against insect and fungal attack by a suitable qualified and experience specialist.
Roof Coverings & roofing felt - Should be in a sound and weather tight condition; any
defective coverings/felt should be replaced with matching new/existing sound coverings, fixed
as manufacturer’s details.
Ceilings- To the underside of the new storey floor should achieve 30 minutes fire resistance.
Normally 13mm plaster board & skim or sound lath and plaster in older houses will achieve this,
otherwise additional upgrading will be required.
Internal space available – The roof space should not have any chimneys or services passing
centrally through the loft space that cannot be easily moved, altered or modified by suitable
experienced and qualified property professionals. Structural alterations/modifications should be
in compliance with details and calculations carried out by a suitable qualified and experience
property professional.
Head room available- Is measured vertically from the top of the new floor (which typically can
be 200mm above the existing ceiling joists) to the underside of the new horizontal/sloping
ceilings (which can typically down stand 50 -75mm from the existing roof structure). A minimum
headroom of 2.0m is required at the head of the stairs to comply with building regulations. A
ceiling height of 2.2 to 2.3 is preferred in the centre of the roof in habitable rooms reducing to
0.800 to 1.2m for the side walls on sloping ceilings so low furniture can be placed in front of
them. If your existing roof pitch is less than 30 degrees and roof span is less than 6 metres, a
loft conversion may be impractical and the only possibility may be to remove the roof completely
and replace it with attic trusses suitable for rooms in the roof designed by a specialist.
Means of escape- Three storey houses will require a protected stairs that connects to a hall
and final exit at ground floor level or give access to at least two escape routes to final exits at
ground level which will require separated by fire resisting construction and fire doors.
Alternatively, the new top storey can be separated by fire resisting construction and provided
with an alternative escape route (subject to planning permission), or a domestic sprinkler
system can designed by a fire engineer. The full means of escape and fire safety requirements
are covered in detail later in this guidance.

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10.0 General technical & practical guidance for loft conversions
A1: Preparation, protection, access & demolition
Provide all necessary scaffolding, access ladders, material hoists, temporary protection and
working platforms etc for the loft conversion which are to be erected, maintained, certificated,
dismantled and removed by suitably qualified and insured specialists.
All plumbing, drainage, heating, electrical services etc including re-siting of heating appliances/
boilers/ flues /tanks etc to be altered /modified /adjusted as necessary by suitably qualified &
experience specialists or registered competent persons, tested & appropriate certification
issued where required in this specification.
Any asbestos is to be inspected by a specialist, removed and disposed off site by a specialist-
licensed contractor in compliance with the Control of Asbestos Regulations 2006.
Prior to and during works, the person carrying out the works is to liaise with and meet the
requirements of the relevant Service Authorities, including the location and protection of all
services as necessary.
The builder is to allow for and maintain all temporary protection to the building to maintain
weather tightness until completion of the works. All structural timber is to be grade C24, stress
graded to BS 4978 and sawn to BS 4471. All timber is to be protected on site to minimize
moisture content which must not exceed 22%.
A2: Inspection of the existing roof & structure
Existing foundations, lintels and wall structure that will be built off or support the new storey
loads from the proposed works may need to be exposed at the discretion of the Building Control
Surveyor and structural engineer to ensure that they are adequate and suitable - this may
include opening up or excavating walls/floors (and making good to match the existing) to check
internal foundations or walls. If they do not appear to be adequate to support the proposed
works, details/justification of the proposed remedial works/alterations including necessary
engineering calculations and details will need to be submitted for approval before works
commence on site.
A3: Alteration, modification & strengthening of the existing roof & structure
Over haul existing roof coverings and structural timbers as necessary, replace defective and
missing tiles, treated timber battens, roofing felt, lead valleys, flashings, facia boards, soffit/
barge boards and rainwater goods etc as necessary to match existing. Repoint/ rebuild
defective masonry walls/ chimneys etc as necessary. Repair/ replace defective roof timbers as
necessary. Existing timbers to inspected, repaired, replaced and treated as necessary by a
specialist with a warrant backed guarantee against insect & fungal attack.
Alteration/modification/strengthening of the existing roof structure/structural members/ walls etc
should only be carried out/repaired/ replaced/ supported or removed in strict compliance with
details and calculations received from a suitably qualified person. These details must be
approved by building control before works commence on site.
Trussed rafter roofs constructed using a series of complex trusses should only be altered,
modified and converted in compliance with details and calculations carried out by a suitable
qualified and experience property professional. No trussed rafter should ever be cut or modified
in any way until a new supporting structure is in place which has been designed by a suitably
qualified and experienced specialist designer. Further information for loft conversions with
trussed rafter roofs can be obtained from TRADA at: www.tra.org.uk

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Diagram 1: Typical plan layout of a loft conversion with dormer pitched roof (not to scale)
EXISTING SEPARATING
WALL
Upgrade sound
insulation to separating
walls between dwellings
as necessary as
guidance details
13mm vapour checked plaster board & skim
12mm structural plywood skin & fixings to s/engineers details &
calculations
100mm timber studs at 400mm ctrs
Thermal insulation fixed between studs as guidance details
Load bearing studs supported by structural beams to
s/engineers details & calculations
ADJOINING
UNHEATED ROOF
SPACE
13mm vapour
checked plaster
board & skim
75 x 50mm timber
studs at 400mm ctrs
fixed to wall
Insulation fixed
between studs as
guidance details
FD 20 fire
door
Smoke alarm
30 minutes fire
resisting (&
sound
insulating) stud
partition to
protect stairs as
guidance
details
Stairs & handrail
as guidance
details
Existing walls with a
threshold U value worse
than 0.7, upgrade U value
to 0.55 for cavity walls & 0.3
for solid walls as follows:
13mm vapour checked
plaster board & skim
75 x 50mm timber studs at
400mm ctrs
fixed to wall
Thermal insulation fixed
between studs as guidance
details
Load bearing stud with thermal
insulation as detailed below
Internal sound insulated stud
partition as guidance details
Proposed dormer
roof omitted for
clarity of layout

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Diagram 2: Typical section through a loft conversion with dormer pitched roof (not to
scale)
Diagram 3: Typical section through a loft conversion with dormer flat roof (not to scale)
12mm plywood gusset screwed
High level roof vents equal to
a continuous 5mm air gap with
fly screen if not breathable
type felt
If existing rafter undersized fix
additional rafters alongside
existing -birds mouthed over
& fixed to structural stud
Roof insulation -see options
in guidance notes
13mm vapour checked
plaster board with
skim finish
Ceilings to achieve
30 minutes fire
resistance from under
side
Structural stud partition as
s/engineers details, insulated as
detailed in guidance notes, with
13mm
v.c.plaster board and skim finish
Structural beam to s/engineers
details & calculations
Trimming joists &
rafters to
s/engineers details
& calculations
Ceiling joists- see guidance
notes for sizes
Floor joist sizes - see guidance
notes for sizes suitable for spans
and spacing for noggins
Sound insulation - see guidance notes
22mm thick moisture resistant t & g floor boards
Note: see guidance notes for fire safety
requirements, stairways /guarding
details & checking exisitng foundations
& lintels to support new storey loadings.
Existing roof coverings
Dormer roof constructed as typical roof
section detail and supported on timber
wall construction with finishes to match
existing or as stated in planning permission.
See guidance noted for construction details.
Trimming joists and rafters supporting dormer
roofs to s/engineers details and calculations.
Double glazed window and means of escape
openings as detailed in guidance notes
Code 5 lead flashings
High level roof vents as main roof
NOTE: Alterations to existing
roof structure including removal
of structural members etc must
be in compliance with structural
engineers details & calculations
which must be approved by
building control before works
commence on site.
joist
hanger
Lay 150mm fiberglass insulation
between joist and additional
170mm accross joists or other
approved (U value 0.16). Ensure
50mm clear air space to underside
of non breathable felts at eaves
junction
Eaves ventilation required
equal to a continuous 25mm
air gap with fly screens both
sides of roof if not breathable
type felt
Eaves ventilation required equal to a
continuous 25mm air gap with fly screens
both sides of roof if not breathable type
felt
Roof insulation & ventilation
as detailed on other
roof pitch
Roof insulation -see options
in guidance notes
High level roof vents equal to a continuous 5mm air gap with fly
screen if not breathable type felt increase to 25mm to cross
flat roof (excludes warm roofs)
If existing rafter undersized fix additional rafters alongside
existing -birds mouthed over & fixed to structural stud
Roof insulation -see options in guidance notes
13mm vapour checked plaster board with
skim finish
Eaves ventilation required equal to
a continuous 25mm air gap with
fly screens both sides of roof if
not breathable type felt
Ceilings to achieve
30 minutes fire
resistance from under
side
Structural stud partitions as
s/engineers details, insulated as
detailed in guidance notes, with
13mm v.c.plaster board and
skim finish
Structural beams to s/engineers
details & calculations
Ceiling joists-see guidance
notes for sizes
Floor joist sizes - see guidance
notes for sizes suitable for spans
and spacing for noggins
Sound insulation - see guidance notes
22mm thick moisture resistant t & g floor boards
Roof insulation and eaves
ventilation as detailed on other
roof pitch
NOTE: Alterations to existing roof structure
including removal of structural members
etc must be in compliance with structural
engineers details and calculations
which must be approved by building
control before works commence on site.
joist
hanger
NEW FLAT ROOF
Single ply polymeric or three ply built up felt roofing in bitumen water proof
coverings applied by flat roofing specialist as spec.
22mm external quality plywood decking or other approved
Treated timber firing strips cut to 1:60 min gradient- laid with falls to gutter (allow
50mm min air gap in depth of firing strip from u/side of deck to top of insulation
50mm min air gap
Insulation fitted below roof deck (cold roof & will require cross ventilation as
detailed) or insulation fixed above deck (warm roof and will not require any
ventilation). See guidance notes for flat roof insulation options
13mm plasterboard with foil backing or 500g polythene to provide a vapour check
50mm welted drip on galvanized plate to centre line of gutter fixed to 75mm deep
timber nosing piece
Matching Upvc gutters, facia/barge board with 25mm continuous air gap
with insect screen
Timber lintel to s/engineers details & calculations
Strip back & refix roof coverings with new roofing felt & treated battens
as necessary, dress flat roof membrane over plywood & tiling fillet
(150mm min above flat roof) to provide water proof junction. Provide
temporary protection & support as guidance notes
Suggested ridge detail- steel ridge beam supported on pad stones into
load bearing walls/intermediate load bearing columns, with 50mm
deep treated timber plate bolted to top of beam, rafters birds mouthed
over plate and mechanically fixed.
Bitumen bedded stone chippings covering the whole roof surface to a depth of 13mm
To achieve a class AA designation in close proximity of boundary for spread of flame
Treated flat roof joists fixed to beam with heavy duty galvanized hangers,
fixed to treated wall plates bolted to web of beam. Flat roof joist sizes
and spacing to suit clear spans as guidance notes
Matching double glazed window fitted with means of esape
openings in bedrooms (or inner rooms) see guidance noted for
details
Matching painted render on stainless steel lath with drained cavity
or vertical tile cladding on insulated stud walls - see guidance
notes for details
Code 5 lead flashings (and soakers to tile/roof junction)
Proprietary high level roof vents equal to a continuos 5mm air gap
fitted with insect screen
Lay fiberglass insulation between
joists and additional layer across joists
(or other approved) as guidance
details. Ensure 50mm clear
air space to underside of non
breathable felts at eaves junction
Note: see guidance notes for fire safety requirements, stairways /guarding
details & checking exisitng foundations & lintels to support new storey loadings.

- 13 -
A4: New pitched roofs
Pitched roof coverings
Roof covering to consist of matching slate or tile and associated capping, verge/eaves details
fixed in accordance with manufacturer’s details for pitch and exposure as detailed on the
drawings. Cladding to be fixed to a minimum 25 x 50mm treated timber batten or to
manufacturer’s directions and roof timbers to be overlaid with un-tear able breathable/non
breathable roof felt underlay to BS 747 or relevant BBA certificate.
Roof to be formed from kiln-dried stress graded timbers sized, spacing, spans, bracing and
fixings as detailed on the drawing or tables below. Alternatively, the roof may be formed from
proprietary prefabricated manufactured trusses/attic trusses and bracing to BS 5268 but both
with a foil backed 12.5mm plasterboard and skim ceiling finish.
Pitched roof structure
Roof to be constructed using either manufactured roof trusses or a cut roof as follows:
Roof trusses (including attic & girder trusses)
Roof to be constructed using specialist designed and manufactured trusses (or Attic trusses
where forming room in the roof) @ 600ctrs (max) to BS 5268:3 1985 A2 94. Trusses to be fixed
and braced strictly in accordance with manufacturers details and mechanically fixed to 100 x
50mm sw treated wall plates via galvanized steel truss clips. Reinforced concrete pad stoned
required to support girder trusses to details and calculations by a suitably qualified person.
The person carry out the building work is to check and confirm the actual roof pitch to the truss
manufacturer prior to placing an order. Details of trusses to be prepared by specialist
designer/manufacturer, submitted and approved by building control prior to commencing roof
construction.
Cut roof construction
Roof to be constructed using kiln dried –stress graded timber. Rafters, ceiling joists, purlin,
hanger and binder sizes as stated on tables below or see TRADA Span Tables- suitable for the
proposed clear spans and all properly fixed together using approved fixings.
Where the ceiling joists are raised above wall plate level they must be fixed within the bottom
third of the rafter using 12mm diameter high tensile bolts and steel toothed connectors to
connect each rafter and ceiling joist to prevent possible roof spread. Joists raised above this
level are to be designed by a suitably qualified person and approved by building control before
works commence.
Struts & braces to be 100 X 50mm, hips to be splayed rafter depth + 25mm (under 30 degree
pitch the hips are to be designed by a suitably qualified person), lay-boards to be the splayed
rafter depth + 25mm X 32mm thick, ridges to be splayed rafter depth + 25mm, all valleys beams
are to be designed by a suitably qualified person, wall plates to be 100 x 50 fixed to inner skin of
cavity wall using galvanized strapping as detailed below.
Hip rafters to have 100 X 75mm angle ties connected across wall plates in housed joints at
corners of roof & hip irons screwed to hip rafters.
Soffits, fascias and barge boards etc to match the existing or in UPVC to BS 4576, fixed in
compliance with manufacturers details.
Allow for all necessary alteration/modification of any existing adjoining roof as required to
enable the proper completion of the works and in agreement with building control.

- 14 -
Allow for building in as work proceeds or insertion of proprietary stepped/cavity tray dpc to
follow line of new roof 150mm above all roof/wall abutments as necessary using code 5 lead
flashings. Tie the new roof into the existing, alter/modify/renew existing roof coverings and form
a weather tight structure.
Fix 12.5mm foil backed plasterboard (joints staggered) and 5mm skim coat of finishing plaster to
the underside of all ceilings using galvanized plasterboard nails.
Roof pitch to (single storey) single skin buildings with walls 100mm thick should not exceed 40
degrees without structural engineers details & calculations to confirm stability of the structure.
Cut roofs over 40° are to be braced to BS 5268.
Table 1: Spans for Common Domestic Timber Rafter Sizes at 400mm spacing
(Strength Class C24)
Slope of Roof (degrees)
15-22 22-30 30-45
Size of Rafter
Breadth X Depth (mm)
Maximum clear span (m)
47 100
47 125
47 150
47 170
47 195
2.52 2.58 2.66
3.15 3.22 3.32
3.76 3.85 3.97
4.36 4.45 4.57
4.87 4.98 5.14
Table 2: Spans for Common Domestic Timber Ceiling Joist Sizes at 400mm spacing
Size of Ceiling Joist
Breadth X Depth (mm)
47 97
47 120
47 145
47 170
47 195
47 220
1.93
2.56
3.37
4.00
4.73
5.47
Table 3: Spans for Common Domestic Timber Purlin Sizes (Strength Class C24)
Slope of Roof (degrees)
15-22 22-30 30-45
Size of Purlin
Breadth X Depth
(mm)
Spacing of Purlins (mm)
1500 1800 2100 1500 1800 2100 1500 1800 2100
75 125
75 150
75 175
75 200
75 225
1.87 - - 1.91 - - 1.98 1.86 -
2.24 2.10 1.99 2.29 2.15 2.04 2.37 2.23 2.11
2.61 2.45 2.32 2.67 2.51 2.38 2.76 2.59 2.46
2.98 2.80 2.65 3.05 2.87 2.71 3.16 2.96 2.81
3.35 3.15 2.98 3.43 3.22 3.05 3.55 3.33 3.15

- 15 -
Table 4: Permissible Clear Spans for Common Ceiling Binders Sizes
Size of Binder
Breadth X Depth
(mm)
Spacing of Binders (mm)
1200 1500 1800 2100 2400 2700
47 150
47 175
63 150
63 175
75 150
75 175
2.19 2.06 1.96 1.87 1.80 -
2.60 2.45 2.32 2.22 2.13 2.05
2.45 2.31 2.20 2.10 2.02 1.95
2.91 2.74 2.60 2.48 2.38 2.30
2.62 2.47 2.35 2.25 2.16 2.08
3.11 2.92 2.77 2.65 2.55 2.46
Diagram 4: Typical section through a pitched roof (not to scale)
Roof restraint
Roof and walls to be provided with lateral restraint straps across at least 3 timbers as noted in
wall section at ceiling, wall plate and verge levels with 30 x 5mm x 1m galvanized metal straps
or other approved to BSEN 845-1 at maximum 2m centers.
Roof slates/tiles to match existing or as stated in planning permission
fixed as manufacturers details and suitable for the pitch
Breathable or non breathable roofing felt fixed as
manufacturers details
25 x 50mm treated battens at a guage to suit coverings
Rafters (see construction details and table
in specification for sizes of rafters suitable for
clear spans)
Ceiling joists (see construction details and table
in specification for ceiling joist sizes suitable
for clear spans
Rain water gutter
Facia/soffit boards
Eaves ventilation equal
to a continuous 10mm
air gap with insect screen
(may not be required
with certain breathable
roof membranes)
Double glazed window bedrooms/
inner rooms to be fitted with openings
suitable for escape as detailed in
the specification
Wall plates
(strapped at
2.0m ctrs)
Continuous
insulation
Proprietary insulated steel lintels suitable for spans and
loadings in compliance with lintel manufactures
standard tables
Sound insulated
stud partition as
detailed in
specification
Ridge tiles to match roof coverings
Ridge board (see specification for details)
Hangers to support hangers if additional support is
required to ceiling joists (contact building control for
details)
Binders to support ceiling joists if they require additional
support (contact building control for details)
Roof insulation (see options in specification
Galvanized steel strapping at 2m ctrs built into
cavity and fixed over 3 rafters with noggins as
detailed in specification
Vapour checked plaster board
NOTE: Proprietary high level roof vents to be installed
where insulation follows slope of roof- equal to a
continuous 5mm air gap with insect screen

- 16 -
Roof insulation
Insulation to be fixed to manufactures details and must be continuous with the wall insulation
but stopped back at eaves or at junctions with rafters to allow a 50mm air gap in ventilated cold
roofs.
Table 5: Insulation laid horizontally between and over ceiling joists
(Vented cold roof achieving a U-value of 0.16 W/m².k)
Product K -Value Position in roof
Crown Wool &
Rock-wool Roll
0.036-0.037 150mm between joists &
150mm laid across joists
Alternatives TBA
Table 6: Insulation fixed between/under rafters
(Vented cold roof achieving a U-value of 0.18 W/m².k)
Kingspan Kooltherm K7
Or other approved with a K
value of 0.020
0.020
0.021
100mm friction fixed between
rafters &
42.5mm fixed under rafters*
Alternatives TBA
* Where rafters are only 100mm deep, battens should be provided to their underside to maintain
a 50mm air gap above the insulation where a non breathable roofing felt is used or battened to
allow a 25mm sag in felt if using a breathable roofing membrane as the manufacturers details.
Table 7: Insulation fixed between/over rafters
(Warm roof achieving a U-value of 0.18 W/m².k)
Kingspan Kooltherm K7
value of 0.020
0.020 50mm fixed between rafters &
55mm fixed over rafters
Alternatives TBA
25 x 50mm counter battens to be fixed over insulation to allow for sag in
breathable roofing membrane as manufacturers details

- 17 -
Diagram 5: Typical roof valley detail (not to scale)
Diagram 6: Typical section through a dormer roof (not to scale)
200mm
min
125mm
min
Roof coverings & roof structure as
specification
& section details
Breathable roofing membrane
lapped over lead & forming drip
Tiling fillet
Code 5 lead lined gutter- lead sizes,
drips & welted joints etc to the Lead
Development association details
25mm treated gutter board fixed to:
50 x 50mm treated timber gutter
bearer
Rafter birds
mouthed over 150 x
50mm wall plate
(wall plated
strapped at 2.0m
ctrs
Pcc pad stone or
dense blockwork
Roof slates/tiles to match existing or as stated in
planning permission fixed as manufacturers details and
suitable for the pitch
25 x 50mm treated battens at a guage to suit coverings
Breathable or non breathable roofing felt fixed as
manufacturers details
Ridge board as specification
Rafters (see construction details and
table in specification for sizes of rafters
suitable for clear spans)
Ceiling joists (see construction details
and table in specification for ceiling
joist sizes suitable for clear spans
Insulation deatils as tables in
specification
Dormer walls constructed with painted
renders or cladding on insulated
timber frame as spec details
Code 5 lead flashing & valleys
Dormer roof supported on rafters
doubled up & bolted together
See main roof for
construction details
Rain water gutter, facia/soffit
boards etc as spec
Eaves ventilation equal
to a continuous 10mm
air gap with insect screen
(may not be required
with certain breathable
roof membranes)
13mm vapour checked plaster
board & skim
Trimming
joists as
spec

- 18 -
Roof ventilation
Roof insulation to be continuous with the wall insulation but stopped back at eaves or at
junctions with rafters to allow a 50mm air gap. Cross ventilation to be provided by a proprietary
eaves ventilation strip equivalent to a 25mm continuous gap at eaves level with insect grill.
Alternatively, where cross ventilation is not possible such as mono pitch, coved ceiling or room
in the roof provide additional ridge/high level ventilation equivalent to a 5mm gap in the form of
proprietary vent tiles spaced in accordance with manufacturer’s details.
Ventilation to the roof space may be omitted, only if a proprietary BBA or similar approved
breathable roof membrane, with minimum 25mm thick treated vertical counter battens and
proprietary eaves carrier system is used. Breathable roof membranes & proprietary roof vents
must always be installed as manufacturers details (note: some breathable membranes may also
require additional roof ventilation)
A5: Flat roof construction
Flat roof to be carried out as detailed on the drawings. Moisture content of timber should not
exceed 20% and to be kiln dried & grade C24. Workmanship to comply to BS 8000:4. All fixings
to be proprietary stainless steel or galvanized steel.
Waterproof coverings: to be either:
 3 layers of high performance felt (hot bonded together with bitumen) to a current BBA
Certificate in compliance with BS8217
 Single layer system with a current BBA or WIMLAS Certificate
 Glass reinforced plastic (GRP) system with a current BBA or other approved
accreditation
 Lead sheet fixed in compliance with the Lead Development Associations guide to good
practice or in compliance with the Lead Sheet Associations technical guidance sheets
available from: www.leadsheet.co.uk.
 Mastic asphalt fixed in compliance with the Mastic Asphalt Councils technical guides &
specifications
Waterproof covering to be laid in compliance with manufacturers details by flat roofing specialist
onto separating layer over roof insulation layer in compliance with Table 14 below to form a
‘warm roof’ (or alternatively insulation fixed between/under joists in compliance with Table 13
below forming a ‘cold roof’) fixed to, 22mm external quality plywood decking or similar approved
laid to 1:60/80 minimum gradient using firing strips at spacing to match joists, fixed onto timber
flat roof joists constructed of kiln dried structural grade timber with sizes and spacing suitable for
the proposed clear span as annotated on the drawing or in compliance with Table 9 below.
Surface finish to flat roofs: to consist of bitumen bedded stone chippings covering the whole
surface to a depth of 12.5mm to achieve a class AA, AB or AC fire rated designation for surface
spread of flame.
Restrain flat roof to external walls by the provision of 30 x 5 x 1000mm lateral restraint straps at
maximum 2000mm centers fixed to 100 x 50mm wall plates and internal wall faces
Flat roof insulation to be in compliance with tables 13 & 14 below. Flat roof insulation is to be
continuous with the wall insulation but stopped back to allow a continuous 50mm air gap above
the insulation in ventilated cold decks. Cross ventilation to be provided on opposing sides by a
proprietary eaves ventilation strip equivalent to a 25mm continuous gap at eaves level with
insect grill. Note: Warm roof applications ie insulation above the structural deck do not require
ventilation.

- 19 -
The design, workmanship & selection of materials should comply with Model Specification
Sheet P.L.1 Built-Up Roofing: Plywood Deck, published by The British Flat Roofing Council.
Metallic roof trims to be of non-corrodible material & resistant to sunlight & not fixed through the
water proof covering. All timber to be treated using CCA vacuum/pressure or O/S double
vacuum to BS 5268:5, including all cut ends of timber etc 300mm of any joint.
All flat roofing works to be carried out by a specialist flat roofing contractor and all materials etc
to be fitted in compliance with manufacturer’s details. Work should not be carried out during wet
weather or when the deck has not fully dried out. A 500g vapour control barrier is required on
the underside of the roof below the insulation level. Fix 12.5mm foil backed plasterboard (joints
staggered) and 5mm skim coat of finishing plaster to the underside of all ceilings using
galvanized plasterboard nails.
Diagram 7: Typical section through a flat (cold) roof (not to scale)
Table 8: Spans for Common Flat Roof Joist Sizes (Strength Class C24) Access for
maintenance and repairs only
Size of joist
Breadth X Depth
(mm)
Spacing of joist (mm)
400 450 600
47 97
47 120
47 145
47 170
47 195
47 220
75 220
2.02 1.99 1.90
2.65 2.61 2.46
3.36 3.27 2.97
3.98 3.83 3.48
4.55 4.38 3.98
5.13 4.93 4.49
5.94 5.73 5.23
Welted drip
Rain water gutters, facia/
barge board
25mm continuous air gap
with insect screen
Proprietary steel box beam as
manf details suitable for clear span
or timber lintel to s/engineers
details & calculations to suit clear
spans of openings
Water proof coverings applied by flat roofing specialist as spec.
External quality structural decking
Firing strips at 1:60 min gradient
50mm min air gap
Insulation to achieve a min U value of
0.2, fixed above or below structural
decking as above tables
Plasterboard with vapour check
Flat roof joist sizes and spacing as
spec tables
13mm diam stone chippings bedded in hot bitumen
Welted drip
25mm continuous air gap
with insect screen
wall plate & strapping as
spec details
Cavity wall as spec details
1:60/80 gradient
Note: if insulation is fixed above the structural deck (forming a
warm roof) the above ventilation details can be omitted

- 20 -
Table 9: Insulation Fixed Between/Under Flat Roof Joists
(Vented ‘cold roof’ achieving a U-value of 0.18 W/m².k)
Kingspan K7
Kingspan K18
Or other approved with a
K value of 0.020
0.020
0.021
140mm between joists (2 x 70mm)
32.5mm fixed under joists
Note: The joist depth must be sufficient to maintain a 50mm air gap above the
insulation and cross ventilation to be provided on opposing sides by a
proprietary ventilation strip equivalent to a 25mm continuous gap at eaves level
with insect grill for ventilation of the roof space.
Table 10: Insulation Fixed above Flat Roof Joists
(Non vented ‘warm roof’ achieving a U-value of 0.18 W/m².k)
Product K -Value Insulation fixed above deck
Kingspan Thermaroof
value of 0.020
0.020 120mm fixed above deck in a single
layer
Alternatives TBA
Valleys and lead work
Lead work, flashing, soakers, valleys and gutters, etc, to be formed from Code 5 lead sheet and
fully supported on treated valley boards, etc, and to have a minimum 150mm lap joints, dressed
200mm under tiles, etc, and not to be fixed in lengths exceeding 1.5m and to be fixed in
accordance with the roof cladding manufacturers and the Lead Development Association
recommendations.
Lofts hatches, doors & Light wells to roof spaces
All hatches, doors and light wells in the roof space to be insulated to the same standard as the
roof, draft stripped and positively fixed.

- 21 -
A6: New external walls
Cavity walls (U-value 0.28 W/m².k - area weighted average value)
Walls to consist of either approved reconstituted stone facings,100mm tooled flush jointed
brickwork or 2 coat rendered 100mm dense concrete blockwork external skin dependant upon
exposure with a 100mm thick lightweight high performance 2.8N/mm² insulation block with
either a 13mm lightweight plaster finish or 12.5mm plasterboard skimmed dry lining. Where
required external natural stone facings to be tied to external block work with wall ties as detailed
below and foundation widths increased by 150mm.
Walls to be built with 1:5/6 cement mortar and tied with BBA approved stainless steel wall ties
suitable for cavity width at maximum spacing of 750mm horizontal (increased to 600mm if
retaining partial fill insulation using proprietary retaining rings as manufacturers details), 450mm
vertical and 225mm at reveals, verges and closings for cavities up to 100mm wide.
Cavity width and insulation details to be constructed as Table below to achieve a U- value of not
more than 0.28 W/m².k. Wall insulation to be continuous with roof insulation level and taken
below floor insulation levels as manufacturer’s details.
Table11: Insulation requirements for external cavity walls with 100mm dense
Brick or rendered block external skin & internal plaster/dry lining plaster finish
Clear cavity
width required
Insulation type &
Minimum thickness
Overall cavity
width required
Internal Block Type
& Thickness
Partial cavity fill
50mm 40 mm Kingspan
Kooltherm K8 or
Other approved with
K value of 0.020
90mm 100 mm insulation
block (k value 0.15 or
lower)
50mm 50 mm Kingspan
Kooltherm K8 or
Other approved with
K value of 0.020
100mm 100 mm dense
concrete block (K
value 1.13)
Alternatives TBA
Full fill
n/a 115mm full fill glass
fiber (K value 0.037)
Suitable for full fill
n/a 100 mm insulation
block (k value 0.15 or
lower)
Alternatives TBA

- 22 -
External timber framed walls with render finish (U-value 0.28 W/m².k - area weighted
average value)
Render finish (to comply to BS 5262) - to match existing or as specified to be applied in 3
coats at least 16mm – 20mm thick overall to render lath. First & second coats 1:3
(cement : sand with plasticizer). final coat 1:6 (cement : sand with plasticizer)- proportions by
volume. Render should be finished onto an approved durable render stop, angle beads or
jointing sections- stainless steel or other approved using drilled or shot fired fixings only.
Stainless steel render lath fixed (using stainless steel staples) to vertical studs at 600mm max
ctrs. laps wired together at 150mm ctrs. (Mesh to be backed by a water resistant membrane) &
fixed to: treated battens - 25 x 50mm preservative treated battens fixed vertically to studs at
max 600mm ctrs using 75mm long hot dipped galv or stainless steel annular ring nails, fixed to:
Breathable membrane- ‘Tyveck or similar approved suitable for timber framed walls to current
BBA certification, fixed to: External quality plywood- 12mm thick marine ply wood (or other
approved) fixed to: Treated timber frame constructed using: 100/150mm x 50mm head & sole
plates and vertical studs at 400mm ctrs, to s/engineers details & calculations. Thermal insulation
board in compliance with table below to be tightly friction fixed between studs with 13mm
vapour checked plaster board fixed to internal face of studs and finished with 3mm skim coat of
finishing plaster. All junctions to have water tight construction & seal all perimeter joints with
tape internally and with silicon sealant externally.
Diagram 8: Typical section through external timber framed walls with painted render
finish (not to scale)
External timber framed walls with cladding finish (U-value 0.28W/m².k - area
weighted average value)
Approved timber/upvc weatherboarding/vertical wall tiling fixed with proprietary rust resistant
fixings to: 50 X 25mm treated battens/counter battens at 400mm ctrs fixed to: Tyvek vapour
permeable membrane suitable for timber framed walls & fixed as manufacturers details to:
12mm WPB ext quality plywood sheathing (joints covered by dpc/battens) fixed to 100 X 50mm
timber studs at 400mm ctrs with 100 X 50mm timber head & sole plates & 2 rows noggins and
diagonal bracing as S/Engineers details. Studs exceeding 2.5m high to be designed by
Structural Engineer. Thermal insulation board in compliance with table below to be tightly
friction fixed between studs with 13mm vapour checked plaster board fixed to internal face of
studs and finished with 3mm skim coat of finishing plaster. All junctions to have water tight
construction & seal all perimeter joints with tape internally and with silicon sealant externally.
Masonry paint finish
16-20mm thick render finish
Stainless steel render lath with water
resistant membrane to stop render
filling cavity
25 x 38mm treated timber battens
at 600mm ctrs fixed vertically to form
drained cavirty
TYVEK or similar breathable membrane
12mm external quality plywood or
other approved
Stainless steel stop bead forming drip
Insect proof mesh (non rust)
100 x 50mm treated stud at 400mm
ctrs
Thermal insulation as guidance
details
board & skim finish
100 x 50mm soleplates fixed to base
Construction details as
guidance

- 23 -
Diagram 9: Typical section through external timber framed walls with cladding finish
(not to scale)
Wall abutments
Vertical junctions of new and old walls to be secured with proprietary profiled stainless steel
metal crocodile type system with a continuous cavity fixed with DPC and pointed with flexible
mastic as manufacturer’s details.
Lintels & weep holes
Proprietary manufactured lintels to current British Standards/Euro codes (including specialist
lintels supporting stone facings) are to be provided over all structural openings. The positions,
types, sizes, end bearings etc of lintels must be in compliance with the lintel manufacturers
standard tables suitable for the proposed loadings and clear spans. Stop end and dpc trays to
be provided above all externally located lintels in compliance with lintel manufacturer’s details.
Weep holes at 450mm centers with at least two per opening.
Structural columns/beams etc
Non proprietary beams/columns including pad stone to be fabricated and installed in
compliance with details and structural calculations carried out by a suitably qualified and
experienced person, which must be approved by building control before works commence on
site. Dpc trays to be provided above all externally located beams. Weep holes at 450mm
centers with at least two per opening.
Expansion joints
External walls should be provided with adequately spaced and sized expansion joints, in
accordance with masonry manufactures details with adequate tying to each side of the joint and
leaf of masonry using stainless steel wall ties (normally at each block height) and sealed
externally with a proprietary flexible mastic sealant. (Normally expansion joints are 10-12mm
wide and spaced vertically at max 12m ctrs in brick work & 6m ctrs in block work)
Strapping and restraint
Walls to be restrained at intermediate floor, ceiling and gable walls by the provision of 30 x 5 x
1000mm lateral restraint straps or other approved in compliance with BS EN 845-1, at maximum
2m centers carried across at least 3 joists or rafters, etc, with a minimum of 38mm wide x ¾
depth noggins.
Cavity Closers
Proprietary acoustic/insulated fire stop cavity closers, or similar are to be provided to all cavity
openings/closings, tops of walls and junctions with other properties.
Upvc weatherboarding/vertical wall tiling
fixed with proprietary rust resistant fixings
25 x 38mm treated timber battens
at 600mm ctrs fixed vertically to form
drained cavirty
TYVEK or similar breathable membrane
12mm external quality plywood or
other approved
Cladding stop fillet & insect proof mesh
100 x 50mm treated stud at 400mm
ctrs
Thermal insulation as guidance
details
board & skim finish
100 x 50mm soleplates fixed to base
Construction details as
guidance

- 24 -
A7: Internal load bearing walls
Internal load bearing timber stud walls
Load bearing timber stud walls to be in compliance with details and calculations by a suitably
qualified and experienced person, which must be approved by building control before works
commence on site.
Typically load bearing stud walls not exceeding 2.5m high are to be constructed of 100 x 50mm
C24 soft wood studs fixed vertically at 400mm ctrs with head and sole plates and intermediate
noggins fixed at 600mm, with thermal insulation friction fixed air tight between studs as detailed
in table below, with 12mm thick structural plywood glued & screwed to the full height & width of
the room side face of the stud wall and finished with 15 mm plasterboard and skim. Insulated &
draught proofed access hatches to be formed between studs. New rafters to be birds mouthed
over and mechanically fixed to head plate, and mechanically fixed to existing rafters by an
approved method.
Diagram 10: Typical section through internal load bearing timber stud wall supporting
roof loads (not to scale)
Table 12 : Insulation requirements to exposed timber framed walls (U-value 0.28 W/m².k)
Insulation Type Minimum Thickness mm
Kingspan Kooltherm K12 or other
approved with a K value of 0.020
90 mm
Alternatives TBA
Internal load bearing masonry partitions
Internal load bearing walls to be minimum100mm thick 7N/mm2 dense concrete blocks (actual
wall thickness must not be less than the wall it supports above), built off suitable foundations
with pre-cast concrete/proprietary steel lintels over openings (in compliance with lintel
manufacturers span tables) and walls bonded/tied to external or party walls with proprietary ties
each course and restrained by floor or ceiling joists/trusses.
New rafter fixed alongside existing, birds mouthed
over & mechanically fixed over new stud
100 x 50mm timber head plate
100 x 50 vertical timber studs at 400mm ctrs
Thermal insulation friction fixed tightly between studs
12mm structural plywood glued & screwed to studs
15mm vapour checked plaster board & skim
100 x 50 timber sole plate
New structural beam supporting load bearing stud
to s/engineers details & calculations

- 25 -
A8: Internal non load bearing partitions
Internal masonry non-load bearing partitions
Internal non-load bearing partitions to be constructed of 100mm 2.8/mm² dense concrete blocks
built off a thickened floor slab and tied/block bonded to all internal and external walls at
maximum 225mm centers with either a plaster or dry lined finish as the external walls.
Internal timber studwork non-load bearing partitions
Non-load bearing stud partitions are to be constructed of 100 x 50mm soft wood studs, fixed
vertically at 400mm ctrs with head and sole plates and intermediate noggins fixed at 600mm
with a minimum of 25 mm of 10Kg/m² proprietary sound insulation quilt suspended in the stud
and finished with 15 mm plasterboard and skim both sides.

- 26 -
A9: Upgrading existing external walls
Where existing external walls are to be used as part of the loft conversion and have a threshold
U-value worse than 0.7, the U-values should be upgraded to 0.55 for cavity walls & 0.3 for solid
walls. Upgrade walls typically using 75 x 50mm soft wood studs at 400mm ctrs fixed vertically to
existing walls with mechanical fixings (with a strip of damp proof course between stud & wall if
there is a risk of moisture penetration), thermal insulation to be friction fixed air tight between
studs as detailed in table below and 15 mm vapour checked plasterboard fixed to studs with
plaster skim finish. Existing solid external walls less than 328mm thick in rendered stone or
brick or less than 250mm thick in rendered blockwork, should be tanked internally with a BBA or
other approved tanking system to prevent the ingress of moisture into the building.
Diagram 11: Typical plan layout of upgrading existing walls in loft conversion (not to
scale)
Table 13: Insulation requirements for upgrading existing external walls
External wall type Insulation Type Minimum
Thickness mm
Cavity walls with threshold U-
value worse than 0.7, upgrade U-
value to 0.55
60 mm
Solid walls with threshold U-value
worse than 0.7, upgrade U-value
to 0.30
70mm
Existing walls with a
threshold U value worse
than 0.7, upgrade U value
to 0.55 for cavity walls & 0.3
for solid walls as follows:
13mm vapour checked
plaster board & skim
75 x 50mm timber studs at
400mm ctrs fixed to dpc
strip & existing wall
Thermal insulation fixed
between studs as guidance
details
Solid external walls less than
328mm thick rendered
stone/brick or less than
250mm thick rendered
blockwork to be tanked
internally with a BBA
approved water proof
tanking system to prevent
ingress of moisture into the
building

- 27 -
A10: Separating (party) walls & floors between dwellings
( Also see relevant sections in ADE)
Masonry party walls separating dwellings (U-value 0.2 W/m2
.K)
Party walls to be constructed of 2 skins of plastered 100mm dense concrete block with a clear
50mm cavity and BBA approved wall ties spaced as external walls up to the underside of the
roof and fire stopped with mineral wool or an approved proprietary intumescent product to
achieve a minimum 45dB value for airborne sound insulation. The party wall is to be
bonded/tied to the inner leaf and the junction of cavities are to be fire stopped throughout its
length with a proprietary acoustic/ insulated fire stop cavity closer and all other vertical and
horizontal cavities are to be closed in a similar manner to provide effective edge sealing and a
U-value of 0.2 W/m2
.K.
Timber frame party walls separating buildings (U-value 0.2 W/m2
.K)
Timber framed stud walls to achieve a minimum 45 dB value for airborne sound insulation and
constructed with 100 x 50mm sawn timber studs at 400mm ctrs with head & sole plates, with 2x
50mm thick layers ROCKWOOL RWA 45 mineral wool friction fixed between studs, and 2x
15mm thick layers of ‘LAFARGE dB check’ wall board fixed both sides of stud (joints staggered)
with skim coat of plaster finish- as wall board manufacturers details. No electrical fittings to be
fixed into/onto party walls & all gaps to be fire sealed & smoke stopped to the full height and
width of the party wall and upto the underside of the roof coverings using mineral wool (not
glass wool) or an approved proprietary intumescent product to provide effective edge sealing
and a U-value of 0.2 W/m2
.K.
Upgrading sound insulation of existing separating walls
Existing wall should be at least 100mm thick, of masonry construction and plastered on
both faces. With other types of existing wall the independent panels should be built on
both sides.
Construct new independent frame fixed at least 10mm from one side of the existing wall
using either; 100 x 50mm timber studs at 400mm ctrs fixed onto head & sole plates or to
a proprietary galvanised metal frame, fixed as manufacturers details. Fix 50mm thick
ROCKWOOL RWA 45 sound insulation or other approved (min density 16kg/m3) friction fixed
between studs
Fix two layers of 15mm thick dB checked wall board with staggered joint and plaster skim
finish to the independent frame using mechanical fixings. Note- allow a minimum
distance of 35mm between face of existing wall & inner wall board face.
No electrical fittings to be fixed into/onto party walls & all gaps to be fire sealed & smoke
stopped to the full height and width of the party wall and upto the underside of the roof
coverings using mineral wool (not glass wool) or an approved proprietary intumescent
product to provide effective edge sealing and a U-value of 0.2 W/m2
.K.
Party floors separating buildings
Outside the scope of this guidance- see relevant sections in ADE
Sound testing requirements
Pre completion sound testing is required for all new/upgraded party walls/floors which
must be carried out by a suitably qualified person or specialist to demonstrate
compliance with Approved Document E and copy of test results sent to building control.

- 28 -
A11: Additional provisions for 3 storey buildings/extensions
Compressive strength of masonry units
The compressive strength of bricks and blocks used in three storey construction is as follows:
(i) Outer leaf of cavity wall – Blocks & bricks to be 7N/mm2 from foundation level upto the
underside of the structural roof.
(ii) Inner leaf of cavity wall – Blocks to be 7N/mm2 from foundation level upto the underside of
the first floor level. Blocks above this level upto the underside of the structural roof to be
2.8N/mm2.
(iii) Internal walls – Blocks to be 7N/mm2 and 140mm thick upto the underside of the first floor
level. Blocks above this level upto the underside of the structural roof to be 2.8N/mm2.
A12: Intermediate upper floor(s)
Floor to be constructed of kiln dried structural grade timber joists with sizes and spacing suitable
for the proposed clear span as annotated on the drawing or in compliance with the tables below.
Joists to be supported by heavy-duty proprietary galvanized metal restraint joist hangers built
into walls or fixed to treated timber wall plates (same sizes as joists) resin bolted to walls at
600mm centers using approved 16mm diameter stainless steel fixings. Alternatively, joists can
be built into walls using approved proprietary sealed joist caps. Joists are to be doubled up and
bolted together for trimmers, under partitions and baths.
Floor void between joists to be insulated with a minimum thickness of 100 mm of 10Kg/m³
proprietary sound insulation quilt, ceiling to be a minimum 15mm plasterboard and skim and
floor joist covering to be a minimum of 20mm softwood tongue and groove softwood boards or
moisture resistant particle/chipboard to give overall 30 minutes fire resistance. Floor joists to be
provided with 1 row of 38 x ¾ depth solid strutting at ends between joist hangers or proprietary
galvanized struts to BS EN 10327 fixed as manufacturers details, at mid span for 2.5 – 4.5m
spans and 2 rows at ¹/3 points for spans over 4.5m.
Diagram 12: Typical section through a loft floor (not to scale)
22mm thick moisture resistant t & g floor boards fixed to joists
Floor joists fixed between existing joists. Joists sizes,
spacing & noggins suitable for clear spans as guidance
notes & tables
100mm thick sound insulation as guidance notes
Steel beam to s/engineers
details & calculations with
100 x 50mm timber plate
bolted to top flange.
(beam fixed above existing
ceiling joists on pad stones)
Ceilings to achieve 30 minutes fire resistance from
under side
Heavy duty galvanised hangers supporting floor
joists. Hangers fixed to timber plate bolted into
web of beam using 12mm high tensile bolts at
800mm ctrs

- 29 -
Diagram 13: Typical section through an upper floor (not to scale)
Table 14: Spans for Common Domestic Floor Joist Sizes (Strength Class C24)
Size of joist
Breadth X Depth
(mm) (mm)
Spacing of joist (mm)
400 450 600
47 97
47 120
47 145
47 170
47 195
47 220
75 220
2.12 2.01 1.75
2.70 2.59 2.34
3.25 3.13 2.84
3.81 3.66 3.32
4.36 4.19 3.81
4.84 4.70 4.29
5.41 5.26 4.91
Table 15: Spans for Common Trimmer Joist supporting Trimmed Joists
Length of trimmed joists (m)
1.0 2.0 3.0 4.0
Size of trimmer (mm) Clear span of trimmer joist (m) supporting
trimmed joists
2 x 47 x 145
2 x 47 x 170
2 x 47 x 195
2 x 47 x 220
2 x 75 x 220
2.68 2.27 1.97 1.68
3.21 2.68 2.33 1.99
3.69 3.09 2.69 2.31
4.17 3.50 3.06 2.62
4.81 4.13 3.62 3.21
Table 16: Spans for Common Trimming Joist supporting Trimmer Joist
Length of trimmer joist (m)
1.0 2.0 3.0 max
Size of trimming joist
(mm)
Clear span of trimming joist (m) supporting
trimmer joist
2 x 47 x 145
2 x 47 x 170
2 x 47 x 195
2 x 47 x 220
2 x 75 x 220
2.62 2.42 2.25
3.08 2.84 2.65
3.54 3.27 3.05
3.99 3.70 3.46
4.66 4.32 4.05
Double glazed window bedrooms/
inner rooms to be fitted with openings
suitable for escape as detailed in
the specification
100mm minimum width insulation block (see
options in specification)
Wall grade insulation (see options in
specification)
50mm clear cavity if using partial fill cavity
wall insulation (see options in specification)
Wall ties and spacings as detailed in
specification
100mm minimum width external wall in
materials to match existing or as specified in
planning permission
Proprietary insulated steel lintels (with dpc
trays and stop ends) suitable for clear spans
and loadings in compliance with lintel
manufactures standard tables
Galvanized steel
straps at 2m ctrs built
into cavity and fixed
over 3 joists with
noggins
Sound insulated stud partition
22mm t & g moisture resistant floor boarding
Strutting between joist (see
specification for spacings)
Floor joists (see construction
details and table in
specification for sizes of joists
suitable for clear spans)
Sound insulation quilt
as specification
Sound insulated plaster
board achieving 30
minutes fire resistance
100mm dense
concrete partitions
precast
concrete/proprieteray
steel lintols, sizes
suitable for clear spans
as manufactures
standard tables
Floor joists doubled
up under partition
walls & baths
Damp proof course
and insulated closer

- 30 -
Sound insulation to floors within the dwelling
Intermediate floors to be provided with sound insulation as described in the relevant floor
section in this document.
SVP pipe boxing
SVP pipe boxing to consist of soft wood framing, 2 layers of 15mm plasterboard and skim and
mineral wall sound insulation quilt. Boxing to be continuously carried up to roof space for soil
and vent pipe and provided with air grills where an air admittance valve is used.
Exposed intermediate upper floors
Semi exposed intermediate timber floors over unheated areas such as garages, porches,
walkways, and canopy’s to be insulated with the following minimum thickness and types of
insulations to achieve a U-value 0.22w/m².k as in Table 6 below. Where the construction is
open to the environment a vapour barrier and proprietary external mineral fiber or similar 30
minute fire and moisture resistant boarding is to be applied to the underside of the floor.
Table 17: Insulation requirements to exposed intermediate floors
U-value 0.22 W/m².k
Insulation Type Minimum Thickness
Jablite Jabfloor 70
Celotex & Kingspan
Polyfoam
Rockwool Rockfloor
125 mm
70 mm
100 mm
120mm

- 31 -
Part B: Fire safety & means of escape
Means of escape from single storey dwelling with new second storey
The conversion of Bungalows or similar single storey building to form a new first floor do not
require a protected hall, landing or fire doors, but the supporting floor must still be provided with
30 minute fire resisting construction. The stair may be positioned in a ground floor room such as
living room, provided there is an external door that opens directly to the outside for means of
escape. All rooms or bedrooms on the first floor (except bathrooms or toilets) must be directly
accessible off the stair landing. Smoke detection must be installed as detailed below, with an
additional interlinked heat detector at ceiling level in kitchens which are open to the stairs at
ground level.
Means of escape windows to be fitted with proprietary hinges to open to the minimum required
clear width of 450mm. Escape windows must have minimum clear opening casement
dimensions of 0.33m² and 450mm (typically 450mm wide x 750mm high), located within 800-
1100mm above floor level to all bedrooms and habitable rooms at 1st floor level and inner
habitable rooms on the ground floor. Windows above the ground floor storey and within 800mm
of floor level are to be provided with containment/ guarding/ proprietary catches which should be
removable (child proof) in the event of a fire. Where escape windows cannot be achieved, direct
access to a protected stairs (or protected route to inner rooms) is acceptable in compliance with
the guidance sections below & ADB1- par 2.6 (a) or (b).

- 32 -
Means of escape from two storey dwellings with new third storey
4 options are available:
Option 1: Protected stairway
The new and existing stairs, landings and hallway from the new 3rd
storey down to the ground
floor must be protected and enclosed in 30-minute fire resisting construction and the protected
stairs must discharge directly to an external door as diagram below. 30 minutes fire resisting
construction is required to the underside of the new upper storey floor.
Key to works indicated on diagram above
FD 20: 20 minute fire resisting door to BS 476-22:1987 fitted with intumescent strips rebated
around sides & top of door or frame excludes toilets/bathrooms/en-suite providing the partitions
protecting the stairs has 30 minutes fire resistance from both sides. Existing doors can be
upgraded with proprietary intumescent paint/paper system. (Note: self closing FD30 fire door
with intumescent strips, smoke seals & 100mm high fire resistant thresholds is required
between the dwelling/garage)
SD/HD: Interlinked mains operated smoke alarm/heat alarm with battery back up fitted at ceiling
level to BS 5446 & installed to BS 5839 pt6
Note: Where applicable, any glazing in walls enclosing the protected stairs is to have 30
minutes fire resistance and located 1.1m min above the floor level, and unlimited in the fire
doors. No glazing is permitted elsewhere including between the dwelling & garage unless 30
minutes fire insulated glazing & beading system is installed.
DINING KITCHEN
LOUNGE HALL
BED 2 BED 3
BED 1
LANDING
BATH
ENSUIT
UP
UP
UP
NEW BEDROOM
FD20
FD20
FD20
FD20
FD20
SD
SD
SD
FD20
ALL PARTITIONS
ENCLOSING THE STAIRS
IS TO HAVE 30 MINUTES
FIRE RESISTANCE
INCLUDING GLAZING*
ALL PARTITIONS
FIRE RESISTANCE
INCLUDING GLAZING*
ALL PARTITIONS
FIRE RESISTANCE
INCLUDING GLAZING*
FIRE SEPARATION AT
SECOND STOREY LEVEL
ALTERNATIVELY THE FIRE
SEPARATION CAN BE PROVIDED AT
THE BOTTOM OF THE STAIRS AT
FIRST FLOOR LEVEL

- 33 -
Option 2: Protected stairway with alternative exits at ground floor level
The new and existing stairs, landings and hallway from the new 3rd
storey down to the ground
floor must be protected and enclosed in 30-minute fire resisting construction and the protected
stairs must give access to 2 or more FD20 fire doors on the ground floor that discharge into
different rooms which are separated from each other by 30 minute fire resisting construction
both of each must have external doors for escape as diagram below.
SD/HD: Interlinked mains operated smoke alarm/heat alarm with battery backup fitted at ceiling
LOUNGE
BED 2 BED 3
BED 1
LANDING
BATH
ENSUIT
UP
NEW BEDROOM
FD20
FD20
FD20
FD20
SD
SD
FD20
ALL PARTITIONS
FIRE RESISTANCE
INCLUDING GLAZING*
ALL PARTITIONS
FIRE RESISTANCE
INCLUDING GLAZING*
ALL PARTITIONS
FIRE RESISTANCE
INCLUDING GLAZING*
FIRE SEPARATION AT
SECOND STOREY LEVEL
THE BOTTOM OF THE STAIRS AT
FIRST FLOOR LEVELUP
FD20
cupb
SD
UP
KITCHEN/DINING ROOM
U/SIDE OF STAIRS TO
HAVE 30 MINUTES
FIRE RESISTANCE

- 34 -
Option 3: Fire separated 3rd
storey with alternative external/internal fire exit
The new top 3rd
storey should be separated from the lower storeys by 30 minute fire resisting
construction and provided with an alternative escape route leading to its own final exit as
diagram 3.
The external stairs must not be within 1.8m of any unprotected opening at the side of the stairs,
and no openings are permitted below the stairs- unless the opening is fitted with 30 minute fire
resisting glass and proprietary bead system and is permanently sealed shut- subject to
adequate ventilation.
The external stairs is subject to obtaining planning permission etc where necessary before the
works commence on site. (Please contact the FODDC planning department for further
information).
The alternative fire exit can also be formed internally as a protected stairway.
SD/HD: Interlinked mains operated smoke alarm/heat alarm with battery back up fitted at ceiling
DINING KITCHEN
LOUNGE HALL
BED 2 BED 3
BED 1
LANDING
BATH
ENSUIT
UP
UP
NEW BEDROOM
SD
SD
SD
FD20
PARTITIONS ENCLOSING THE STAIRS IS
TO HAVE 30 MINUTES FIRE RESISTANCE
INCLUDING ANY GLAZING*
FIRE SEPARATION AT
SECOND STOREY LEVEL
FIRST FLOOR LEVEL
EXTERNAL FIRE EXIT STAIRS
(CAN BE AN INTERNAL
PROTECTED STAIRS) SEE
GUIDANCE NOTES

- 35 -
Option 4: Residential sprinkler systems for means of escape
Where fire safety requirements of the building regulations cannot be met for loft conversions,
proposals for fire engineered solutions may be allowed against the requirements of Approved
Document B where a risk assessment has been carried out by a suitably qualified and
experienced fire engineer and approved by building control before works commence on site.
The residential sprinkler system is to be designed and installed to BS 9251:2005 incorporating
BAFSA technical guidance note No.1 June 2008 by a suitably qualified specialist- which must
be approved by Building Control before works commence on site.
If the condition not being met is a ground floor open plan arrangement and the stairs discharge
into a habitable open plan area then a partial sprinkler installation to the whole of all connected
open plan areas may be used. Fire separation of the route will be required from the upper floor
from this open plan area with a 30 minute fire resisting partition and FD20 fire door fitted with
intumescent strips. Instead of the separation it may be possible to fully sprinkler the whole
dwelling and retain the open plan arrangement with the agreement of building control.
With the agreement of the building control, it should be possible to reduce fire protection
throughout the dwelling by 30 minutes with the introduction of a full sprinkler installation.
Contact: The British Automatic Sprinkler Association (BAFSA)- Sprinklers for Safety: Use and
Benefits of Incorporating Sprinklers in Buildings and Structures (2006) ISBN: 0 95526 280 1.
See also: www.bafsa.org.uk ISBN 0-9552628-3-6 technical guidance note no.1 see also
www.firesprinklers.org.uk
IMPORTANT NOTE: The above 4 options need not be followed if the dwelling house has more
than one internal stairway, which afford effective alternative means of escape and are physically
separated from each other.
Fire doors
All rooms onto the protected stairs (except bathrooms or toilets providing the enclosing walls
have 30 minutes fire resistance) are to be provided with FD20 (or FD30) fire doors to BS 476-
22:1987 fitted with intumescent strips rebated around sides & top of door or frame with
intumescent strips. Any glazing within the fire door or stairway enclosure is to have 30 minutes
fire resistance including the beading as detailed in above options.
Existing solid/hardwood doors may achieve the required 20 minutes fire resistance or can be
upgraded with proprietary intumescent products applied as manufacturers details to achieve 20
minutes fire resistance, as agreed with building control before works commence on site. Contact
Cotswold Intumescent Products on: 01453 731006. A copy of the purchase invoice will be
required by building control on completion to confirm product used.
Doors between garages and dwellings to have 100mm high fire resisting threshold step down
into the garage, FD30 fire door & frame fitted with an approved mechanical self closing devise,
intumescent strips and cold smoke seals.
Smoke alarms
All floors to be provided with mains operated interconnected fire detection and fire alarm system
to BS 5446 & installed in accordance with the relevant recommendations of BS 5839 – 6: 2004
to at least a Grade D Category LD3 standard.
Self contained mains operated smoke alarms (heat alarms installed in kitchens) with battery
back up to be fixed at ceiling level in all circulation areas at each storey level, within 7.5m of all
doors to habitable rooms.

- 36 -
Fire resistance to new storey floor
The new 3rd
storey floor storey should be separated from the remainder of the house by 30
minute fire resisting construction e.g. a minimum of 12.5 mm (if existing or 15mm if renewed)
plasterboard and skim to ceilings and sides of stud walls and provided with a 20 minute fire door
with intumescent strips at either the bottom or top of the new stair leading to the loft conversion.
Permitted building openings in relation to a boundary:
Openings within 1.0m of a boundary
An unprotected opening of 1m2
(e.g. window) is permitted every 4.0m on the same building
face. This unprotected opening can consist of two or more smaller openings within an area of
1m2
(openings less than 0.1m2
is permitted every 1500mm on the same building face). There
are no restrictions on dimensions between openings separated by compartment walls & floors.
Please refer to Diagram 20 of ADB4 Volume 1 for full details.
Openings more than 1.0m from a boundary
Permitted unprotected openings to be in compliance with table below for buildings not
exceeding 3 storeys high (excludes basements) or more than 24m long.
Table 18: Permitted unprotected areas in relation to a relevant boundary
Minimum distance between side of
building & relevant boundary
Maximum total area of unprotected
openings
1.0m
2.0m
3.0m
4.0m
5.0m
6.0m
5.6m2
12m2
18m2
24m2
30m2
no limit
If sprinklers are fitted throughout the building to BS 9251, the above distances can be reduced
by 50% (min 1.0m) or the unprotected opening area doubled. Please refer to
ADB4 Volume 1 for full details relating to space separation and other methods of calculating
unprotected areas.
Fire resistance to elements of structure etc
Please refer to Table A1: Appendix A of ADB: Volume 1 for full details.
Table 19: Fire resistance to common elements of structure etc
Building element Fire resistance
in minutes
Method of protection
Beam, column or frame 30 All exposed faces
Load bearing wall 30 Each side separately
Upper floors (Max 3 storey building) 30 Underside
Roof (only if forming part of an escape route) 30 Underside
External walls:
(i) Less than 1.0m to relevant boundary
(ii) More than 1.0m to relevant boundary
(max 3 storey building)
60
30
Each side separately
From inside building
Walls & upper floors separating an integral
garage from the dwelling 30 From garage side
Compartment walls & floors separating
Dwellings 60 Each side separately
Protected stairs & lift shaft (not forming
part of a compartment wall) 30 Each side separately
Cavity barriers etc 30 Each side separately

- 37 -
Note: 13mm plasterboard & skim finish applied to 100 x 50mm timber stud partitions/ ceiling/
floor joists as detailed in this specification will achieve 30 minutes fire resistance, two layers of
13mm plaster board (joints staggered) will achieve 60 minutes fire resistance. Masonry walls
detailed in this specification will achieve 60 minutes fire resistance.
Surface spread of flame: wall & ceiling linings
Table 20: Surface spread of flame: Classification of wall & ceiling linings
Please refer to Table 1: Section 2 of ADB: Volume 1 for full details.
Location National class European class
Small rooms upto 4m2 &
Domestic garages upto
40m2
3 D-s3,d2
Other rooms over 4m2 inc
Garages over 40m2 &
Circulation spaces within
Dwellings (e.g. hall, stairs
& landings)
1 C-s3,d2
Note: Plaster on masonry walls & plaster board & skim linings in this specification will achieve
class 1. Exposed timber linings should be treated with a proprietary treatment to achieve the
above classifications.
IMPORTANT NOTE: Means of escape windows – are not required where the stairs is
protected as detailed above

- 38 -
Part C: Site preparation and resistance to contaminants & moisture
Horizontal damp proof courses & trays (dpc’s)
Horizontal Dpc’s and Dpc trays with weep holes at 1.0m ctrs to be provided 150mm above
ground level continuous with and sealed to the floor Dpm & radon dpc tray.
Vertical damp proof courses & trays etc (dpc’s)
Stepped and horizontal Dpc/cavity trays are to be provided over all openings, roof
abutments/projections and over existing walls with different construction or materials. Install
vertical dpc or proprietary insulated cavity closers at all closings, returns, abutments to cavity
work and openings etc.
Part D: Cavity wall filling with insulation by specialists
The suitability of the cavity wall for filling must be assessed before the works is carried
out by an insulation specialist in accordance with BS 8208: Part 1: 1985.
The insulation specialist carrying out the work must hold or operate under a current BSI
Certificate of Registration of Assessed Capability for the work being carried out.
The insulation material must be in accordance with BS 5617: 1985 and the installation
must be in accordance with BS 5618: 1985
The Installation of urea-formaldehyde (UF) in cavity walls is to be carried out in
compliance with paragraphs 1.1 — 1.2 of ADD1
Part E: Resistance to the passage of sound
New Internal walls & floors in loft conversion
Sound insulation details between internal walls & floors separating bedrooms or a room
containing a WC and other rooms to be carried out in accordance with the relevant
details contained within this guidance and Approved Document E .
New/existing party walls and floors in loft conversion
Sound insulation details for new party walls and floors and upgrading of existing party walls
and floors to be carried out in accordance with the relevant details contained within this
guidance and Approved Document E .

- 39 -
Part F: Ventilation
Purge (natural) ventilation
Purge (natural) ventilation to be provided to all habitable rooms equal to 1/20th
(5%) floor
area where the external windows/doors open more than 30 degrees and increased to
1/10th
(10%) of the floor area where the windows opens between 15 - 30 degrees.
Window openings which open less than 15 degrees is not suitable for purge ventilation
and alternative ventilation details are required as detailed below and in compliance
section 5 & Appendix B of Approved Document F1. Purge (natural) ventilation openings
to habitable rooms to be typically 1.75m above floor level. The area of external windows, roof
windows & doors should not exceed 25% of the usable internal floor area otherwise SAP
calculations may be required from a suitably qualified person to confirm design flexibility where
they exceed 25% of the usable floor area. (ii) See the relevant section in this guidance for
permitted unprotected external openings in relation to relevant boundaries.
Means of escape windows to be fitted with proprietary hinges to open to the minimum required
clear width of 450mm. Escape windows must have minimum clear opening casement
dimensions of 0.33m² and 450mm (typically 450mm wide x 750mm high), located within 800-
1100mm above floor level to all bedrooms and habitable rooms at 1st floor level and inner
habitable rooms on the ground floor. Windows above the ground floor storey and within 800mm
of floor level are to be provided with containment/ guarding/ proprietary catches which should be
removable (child proof) in the event of a fire. Where escape windows cannot be achieved in two
story buildings, direct access to a protected stairs (or protected route to inner rooms) is
acceptable in compliance with the guidance above. Escape windows are not required where
protected routes are provided in compliance with this guidance.
Mechanical extract ventilation & fresh air inlets for rooms without purge ventilation
Mechanical extract ventilation & fresh air inlet are required for habitable rooms without
purge (natural) ventilation which must designed by a ventilation specialist having
a minimum of 4 air changes per hour & manually controlled in compliance section 5 of
Approved Document F1.
Background ventilation
Background ventilation to be provided equivalent to 8000mm² to habitable rooms and 2500mm2
to wet rooms via hit and miss or 2 stage catches fitted to windows
Mechanical extract ventilation rates
Mechanical ventilation is to be provided to the rooms listed below directly ducted to the outside
air equivalent to the following rates.
Kitchen 30 litres per second over hob or 60 litres elsewhere
Utility room 30 litres per second
Bathroom 15 litres per second (including shower rooms & en-suites)
Toilet 6 litres per second W/C (with or without a window)
General requirements for mechanical extract ventilation
Mechanical ventilation to rooms without open able windows to be linked to light operation
and have 15 minutes overrun and a 10mm gap under the door for air supply. Fans must not be
installed in rooms containing open flue appliances unless the interaction of mechanical
ventilation & open flue heating appliances is checked and certified by an approved method &
suitably qualified person as contained in ADJ.
Mechanical ventilation to be ducted in proprietary insulated ducts to outside through
walls to proprietary vent or through roof space to proprietary matching tile /soffit vent

- 40 -
Part G: Sanitation, hot water safety and water efficiency
Sinks with hot and cold running water is to be provided in all food preparation areas,
bathrooms to be fitted with either a bath or shower. Hot & cold water taps to wash basins,
baths, showers & sinks including external taps to have water from a wholesome water
supply. Outlets from domestic hot water storage vessels to be fitted with an in line hot
water supply tempering valve to prevent water temperatures exceeding 60 ºC.
Where a building is converted into a new dwelling, the bath should be fitted with an in line
blending valve fixed at 48 degrees centigrade.
Hot water storage systems to be restricted to 100 degrees C max and outlets from domestic hot
water storage vessels to be fitted with an in line hot water supply tempering valve to prevent
water temperatures exceeding 60 degrees C max.
Hot water storage vessels to be fitted with a non-self-setting energy cut out to instantly
disconnect the power supply.
Wash hand basins to be provided in all rooms containing a w/c and a door must separate the
w/c from any food preparation area in a dwelling
Water tanks/cisterns must have an adequate designed flat platform base to support the
proposed loads.
Pumped small bore foul water drainage from a toilet is only permitted if there is also access to a
gravity draining toilet in the same dwelling. Proprietary pumped foul water macerator systems
must have BBA or other approved accreditation and fitted in compliance with manufacturers
details to a suitable foul water drainage system.
Commissioning certificates for fixed building services are required on completion with
copy sent to building control

Building Control Guidance For Domestic loft conversion

Building Control Guidance For Domestic loft conversion

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Building Control Guidance For Domestic loft conversion