Roof types

ROOF
Building Materials and Technology
S1S2 A, SCMS School of Architecture
Ar. Reshma C Beddyson

Roof?
The uppermost part of a building which is constructed in the form of framework to give
protection to the building against rain, heat, snow, wind, etc.
Building Materials and Technology S1S2 A Ar. Reshma C Beddyson

 To keep out rain, wind, snow & dust
 To prevent excessive heat loss in winter
 To keep the interior building cool in summer
 Designed to accommodate all stresses encountered
 Designed to accept movement due to changes in temperature & moisture
content
 To provide lateral restraint & stability to adjacent walls
 To resist penetration of fire & spread of flame from external sources
Purpose?

Requirements of good roof.
 It should be durable against the adverse effects of various agencies such as wind,
rain, sun, etc.
 It should grant the desirable insulation against sound and heat.
 It should be structurally stable and sound and it should be capable of taking the
loads likely to come over it.
 It should be well-drained.
 It should have efficient water-proofing arrangements.
 It should be fire resistance

Classification based on Shape/ Form

• Flat roof- in plains where rainfall is less and climate is moderate.
• Curved roof- Shells and folded plate roofs are used to cover large column free areas
required for auditoriums, factories etc.
• Pitched roof-wherever rainfall is more.
Classification based on shape

Classification based on shape

A FLAT ROOF is not truly flat but
angled slightly (not more than
10°) to allow for water
runoff. It is the cheapest to build
initially but will cost you much
more than other roof types in
maintenance costs.
Flat roof

Advantages and disadvantages
a) The roof can be used as a terrace for playing and
celebrating functions.
b) At any latter stage the roof can be converted as a
floor by adding another storey.
c) They can suit to any shape of the building.
d) Over-head water tanks and other services can be
located easily.
e) They can be made fire proof easily compared to
pitched roof.
a) They cannot cover large column free areas.
b) Leakage problem may occur at latter date also
due to development of cracks. Once leakage
problem starts, it needs costly treatments.
c) The dead weight of flat roofs is more.
d) In places of snow fall flat roofs are to be
avoided to reduce snow load.
e) The initial cost of construction is more.
f) Speed of construction of flat roofs is less.

Shell roof may be defined as a curved surface, the thickness of which is small compared to the
other dimensions. In these roofs lot of load is transferred by membrane compression instead of by
bending as in the case of conventional slab and beam constructions. Caves are having natural
shell roofs.
Curved roof

The FOLDED PLATE
roof has limited use in
single-family homes.
Modular, prefabricated
roof units are available.
The CURVED PANEL
roof is similar to the
folded plate roof in style
and application. It is
available in
prefabricated modules.

Advantages and disadvantages
a) Good from aesthetic point of view
b) Material consumption is quite less
c) Form work can be removed early
d) Large column free areas can be covered.
a) Top surface is curved and hence advantage
of terrace is lost.
b) Form work is costly.

A sloping roof is known as pitched roof.
These are suitable in those areas where rainfall/snowfall is very heavy.
GABLE ROOF:- This is the
common type of sloping roof
which slopes in two direction.
The two slopes meet at the
ridge.
The hip roof is slightly
more difficult to build
than a gable roof. It is a
popular choice, but does
not provide for
ventilation as well as
some designs.
Forms

The HIP ROOF is slightly more
difficult to build than a gable
roof. It is a popular choice, but
does not provide for ventilation
as well as some designs. A hip
roof is a gable roof with angled
ends taking the place of the
gable end of the structure.
A SHED ROOF is basically a
flat roof with a slightly greater
angle allowing for greater
runoff. They are relatively easy
to build and inexpensive as
compared to most other roof
types. They are usually used on
home extension rooms and
porches

MANSARD roof construction
consists of a compound hip
roof design with a lower and
upper hip format.
A DUTCH roof design is a
hip roof with small able ends
at the ridge allowing for attic
ventilation

GAMBREL ROOF design is
similar to gable construction With
two angles on each side. Steep
lower surfaces and shallow
angle top surfaces allow greater
floor space in 1 ½ story
construction
The BUTTERFLY ROOF is an
inverted gable roof design
creating a central valley for
runoff. The design is visually
stunning but impractical for water
tightness.

The WINGED GABLE is
essentially a gable roof,
extended at the peak.
The A-FRAME ROOF
provides a roof and walls
for the structure. Is
popular for cottages,
homes, churches, and
other structures.

MIXED ROOF STYLE is a
combination of two or more types
of roof such as flat, curved,
pitched etc.,
Combination roof

Roofing Materials

ROOF COVERING FOR PITCHED ROOF
Roof covering is an essential part of pitches roof ,to be placed over the roof frame work.
It protect from rain, snow, sun, wind & other atmospheric agencies.
Selection of roofing materials depends upon:-
a) Type of framework
b) Initial cost
c) Maintenance requirement
d) Appearance
e) Durability
f) Availability
g) Climate

Following are the roof covering materials
a) Thatch Covering
b) Wood Shingles
c) Tiles
d) Asbestos cement sheets
e) Galvanized corrugated iron sheets
f) Light weight roofing
ROOF COVERING MATERIALS

• This is the cheapest roof covering,
commonly used in villages.
• It is very light, but is highly combustible.
• It is unstable against high winds. It
absorbs moisture & liable to decay.
• The framework to support thatch consists
of round bamboo rafters spaced 20 to 30
cm apart & tied with split bamboos laid at
right angles to the rafters.
• In order to drain roof effectively a
minimum slope of 450 is kept.
• The thickness of thatch covering should
at least be 15cm, normal thickness varies
from 20 to 30 cm.
THATCH COVERING roof

• It’s use is restricted to hilly areas where
local timber is easily available at low cost.
• Though it is light weight, it is not fire &
termite resistant.
• It is obtained from well seasoned timber.
• They are obtained in lengths varying from
30 to 40 cm & widths varying 6 to 25 cm.
• They are approximately 10mm thick at the
tail or
• butt end and taper to 3mm.
WOOD SHINGLES roof

It is the oldest type of roof covering
materials &
is still preferred for residential building and
country houses.
This is because country tiles are
manufactured from locally available earth.
Following are the various types of tiles
generally
used:-
A)Plain tiles
B)Curved tiles
C) Italian or Allahabad tiles
D) Interlocking tiles
E) Spanish tiles.
TILES roof

A)Plain tiles B)Curved tiles C) Allahabad tiles D) Interlocking tiles E) Spanish tiles
Pan tiles
THATCH COVERING roof

Following points should be noted while fixing A.C.
sheets:-
• The A.C. sheets should be laid with smooth
side upward.
• End lap and side lap should be properly
maintained. General end lap is 15cm but this
can be varied to suit
• purlin spacing.
• Purlin spacing and length of sheets should be
properly checked before linked.
• The holes for fixing accessories should be
drilled (not punched) in the crown of the
corrugations. The diameter of the holes should
be 3 mm greater than the diameter of the
fixing bolt or screw. Thus 8mm dia. drilled
holes and screwed lightly.
ASBESTOS CEMENT SHEETS roof

• G.I. sheets are also widely used.
• They are stronger than A.C. Sheets.
• Due to higher cost, they are replaced by
A.C. sheets.
• They are not used for slopes flatter than
1in 4.
• G.I. sheets are made from iron sheets
which are galvanized with zinc to protect
them from rusting action of water & wet
weather.
• These sheets are fixed in a manner
similar to A.C. sheets.
GALVANIZED IRON CORRUGATED SHEETS
(G. I. SHEETS) roof

The wide span industrial structures, it is
desirable to reduce the weight of roof , so
that structural framing can be economical.
The light weight roofing materials are of two
types:-
A) Sheeting:-
i) Aluminum Sheet
ii) Asbestos cement sheet
B) Decking:-
i) Wood Wool
ii) Straw board
iii) Aluminum alloy and Steel decking
LIGHT WEIGHT roof

• It is made from wood fibres interwoven
together & cement bonded under
pressure in mould.
• They are available in the form of slabs,
having thickness 12 to 100mm, 0.6m
width & up to 3.9m length.
• It has good sound absorbing & thermal
insulation properties.
WOOD WOOL roof

Classification based on Support
Span is the distance between two intermediate supports for a structure, e.g. a beam or a bridge

In the areas of heavy rain falls and snow fall sloping roof are used. The slope of roof shall be more than
10°. They may have slopes as much as 45° to 60° also. The sloped roofs are known as pitched roofs.
The sloping roofs are preferred in large spanned structures like workshops, factory buildings and ware
houses. In all these roofs covering sheets like A.C. sheet, G.I. sheets, tiles, slates etc. are supported on
suitable structures.
The pitched roofs are classified into;
a) Single roofs
b) Double or purlin roofs
c) Trussed roofs
Pitched roof

(a) Single roofs
Lean to roof (verandah roof)
Couple roof
Couple close roof
Collar beam roof or collar tie roof
(b) Double or purlin roofs
(c) Triple membered or framed or trussed roofs
King post roof truss
Queen post roof truss
Combination of king post and queen post truss
Mansard roof truss
Truncated roof truss
Bel-fast roof truss or latticed roof truss
Composite roof truss
Steel sloping roof trusses
Pitchedroof

Eaves
In the roof, the lower portion of the inclined roof which is projecting
beyond the outer face of the wall. The main function of eaves is to
rainwater to pour from the roof directly on the exterior wall. I also give
protection from sunlight. Sometimes eaves are highly decorated to
increase architectural beauty.
Gable
The Triangular upper part of the wall at the end of a ridge roof.
Flashing
A strip of impervious material, usually metal used to exclude water from
the junction between a roof covering and another part of the
structure.Flashings are provided to prevent moisture from entering the
wall and roof through joints in copings, parapet wall, and other
penetrations through the roof plane.
Hip
The outer angle (more than 180 degrees) formed by the inclined ridge
between two intersecting roof slopes.
Ridge
The horizontal intersection at the apex of the two rising roof surfaces
inclined in opposite directions.
Purlins
These are horizontal members laid on principal rafters on wall-to-wall
to support common rafter of a roof when the span is large. Purlins are
made from wood or steel.
The top surfaces of the purlins shall be uniform and plane. They shall
be painted before fixing on top.
Fascia
This is wooden board fixed to the feet of the common rafter at eaves.
The ends of the lower-most roof covering material rest upon it.
Rafter
Rafter is a structural component of a pitched roof. Typically it starts
from roof support (column or wall) to ridge or hip. Multiple rafters are
used side by side with equal spacing to support the purlin. In typical
home construction, wooden rafters are used. For large industrial of
commercial sheds, steel rafters are used.
Battens
These are thin strips of wood which are fixed on the common rafters
or on the top of ceiling boards to support the roofing materials such
as tiles, sheets, etc. Batten could be also made of metal or plastic.
Terminology

1. It is used covering verandah, sheds and outhouses
connected to main building.
2. Upper side common rafters are supported on a
wall plate which in turn rest on a projecting corbel
stone from the wall.
3. Lower side rest on the wall plate.
4. Roofing material rests on battens, battens on
common rafter and common rafter on wall plate.
Maximum span of the roof is 2.5m
Mono pitched roof structure/ single roof
Lean to roof structure

1. It is formed by a pair of inclined rafters, centre
ridge piece and wall
2. plate for supporting the whole roof.
3. Battens are supported on common rafters and
roofing material on battens
Span of couple roof is limited to 3.5m
Couple roof structure

Similar to couple.
Two rafters are connected by a wooden member which acts
as a tie.
Tie prevents the outward spreading of roof
It can also act as support for ceiling.
It can be economically used for spans up to 4.2m
Couple closed beam roof structure

Members are same but just raising the position of tie
beam.
Used to increase the height of room
For spans between 4 to 4.5m
Couple collar beam roof structure

This roof is similar to the collar beam roof expect
that two collar beams which are crossing each
other to present an appearance of scissors are
provided
Collar and scissors roof structure

Double and purlin roof structure
If span exceeds, the cost of rafters increase and
single roof becomes uneconomical.
For spans more than 5 m double purlin roofs are
preferred.
The intermediate support is given to rafters by
purlins supported over collar beams.
Figure shows a typical double or purlin roof.
Double roof structure

Used over large span: > 6.00m
• Trusses are structurally designed frames based on triangle
principle, serve to carry purlins
• Trusses are spaced at 1800mm centre with the space between
being filled by common rafters
Truss roof structure

For spans of 6.00 –9.00m
• A triangular frame which support the
ridge & purlins, spanned from truss to
truss & carried common rafter & roof
covering
• Roof load transmitted through principal
rafters to wall below
• Principal rafters were bolted to a tie
beam to prevent them spreading under
load
• Strut to prevent sagging
King post truss roof

Spans from 9.00 –12.75m
• Similar to king post but it has 2 vertical
post, strutted apart at their
heads by a straining beam
• Principal rafters are supported by 2
purlins
• Feet of queen post are held in position
by tenons, straps & staining sill
Queen post truss roof

King post
truss roof
Queen post
truss roof

Depending upon the span, trusses of different shapes are used.
https://www.youtube.com/watch?v=MzJAdyWMvRw

Icons for sheets
scales
hatches
Line
weights
Wall
section
Shallow
foundation
Pile
foundation
1
2
3
4
5
6

Thank you

Roof types

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to Roof types

Similar to Roof types (20)

Recently uploaded

Recently uploaded (20)

Roof types