Technical terms and types of roof coverings

Technical terms used in pitched roof



Span:-
 clear distance between the supports.
Rise:-
 vertical distance between ridge and
wall plate.
Pitch:-
 ratio of rise to span.
PREPARED BY : PROF. D.V.PATEL

• Eaves :- lower edge of a sloping roof
• Gable:-If roof slopes in two direction, the closing wall in that portion may
be combination of triangular and rectangular wall.The triangular upper
part of the wall formed at the end of pitched roof is known as Gable.
• Valley:-When two roof surfaces together at an angle less than 180
degree,a valley is formed.

• Purlins:-
–
– wooden members are connected to trusses and to support common
rafters
It placed horizontally over the principal rafter
• Rafters:-
–
– Inclined member placed above the purlins and extend from ridge to
eave.
Common rafters are intermediate rafters, which give support to the
roof covering (30-45cm spacing)

 Batten :-Small c/s of wood, fixed on common rafter to support
roofing material.
 Cleat:-Small pieces of steel or timber, angel or channel section, used
to connect purlins to principal rafter.

STEEL ROOF TRUSSES
 Fabricated from rolled steel
structural members
 Channels, angles, T and plate
sections
Mostly angles used - can resist
both tension and compression
Advantages:
 Economical, Easy to fabricate
Fire proof, Rigid
Permanent, Suitable for speedy
construction

Connections in a roof truss

Types of flat roof
• Madras terrace roof
• Bengal terrace roof
• Reinforced brick cement roof
• Reinforced cement
concrete roof
• Filler slab

Madras terrace roof
 Steps in construction
• Teak wood joist are placed on rolled steel joists.
• Sufficient slope is provided
• Terrace bricks of size 15x75x25mm to be laid diagonally.
• Brick bat concrete of thickness 75mm to be laid
• Rammed and allow to set for three days.
• Flat tiles are then laid over this concrete.
• Surface of this roof is finished with 3 coats of plaster.

Bengal terrace roof
 Used for covering verandah portion.
 Consists of rafters having slight inclination and one end
penetrated into wall.
 Battens are placed over this rafter with spacing 15cm.
 Over that Flat tiles are laid in mortar.
 Surface is finished with fine jelly concrete or flat tiles are
provided.

Reinforced brick cement roof
 Bricks are laid horizontally between the steel bars and concrete mix
is inserted in the joints.
 Top surface of the slab is plastered with a 2cm thick cement mortar.


Over that apply two layers of hot bitumen for water proofing.
Over that bitumen coat apply one more coat of cement paste of
thickness 5cm.
 Provide sufficient slope at top surface for drainage of water

Reinforced cement concrete roof
• Made up of concrete and steel.
Types of roof slab:-
• One way slab:- length/width > 2
• Two way slab:- length/width <
2
• For one way slab
Reinforcement to be run parallel to the
shorter span
• For two way slab
Main reinforcement runs parallel to both
sides of the room
At corners suitable mesh reinforcement to be
provided to resist temperature stressesPREPARED BY : PROF. D.V.PATEL

Filler slab
Concrete slab in which the bottom
portion of the slab is replaced by flat
clay tiles or
Mangalore pattern tiles.
Above the formwork
• Steel reinforcements of designed size are
tied together to form a grid.
• Pairs of clay roofing tiles are placed in the
gap between the reinforcement in line.
• Pour freshly prepared concrete in between
the reinforcement and tiles.
• Level the concrete surface and cured it for
14days.

TYPES OF ROOF COVERING
• Roof covering is depends on the selection of covering material
according to local condition and requirements, such as cost, roofing
structure, availability of material, durability, heat insulation, weight
of covering, fire resistance, slop and so on.
There are many types of roof covering commonly used.
• Thatch covering
• Shingles
• Tiles
• Asbestos- cement sheets
• Slates
• Galvanized corrugated iron sheets
• Sheet metal roof covering
• Bituminous felts
• Glass covering

THATCH COVERING
Mainly used in rural areas
and very low costhouses
The frame work to support
the thatch consists of round
bamboo rafters,
tied with split bamboos and
are placed at right angles at
suitableintervals.
This roofs give very bed
smell due to rotting of
materials it difficult to stay
under the roof, so never
allowed to good work.

SHINGLES
• Shingles are nothing but thin
timber rectangular boards
about 1cm thick.
• Preferred in hilly areas where
wood is easily available at low
cost, in place of tiles orslate.
• Wooden shingles from well
seasoned timber are placed in
a similar manner.
• Shingles length vary from
30cm to38cm and widths
from 6cm to 25cm.
• Shingles do not provide
adequate protection against
cold or heat.

TILES
• The tiles are named
according to their shapes,
sizes and their region.
• Plain tiles, pan tiles, half
round tiles , pot tiles are
some names according to
theirshapes.
• Allahabad tiles, Mangalore
tiles are some of the
patterned tiles derived
names from the regions.
• For laying the tiles a
ground work is prepared
by fixing batten to the
commonrafters,.
• I case of superior work
tiles are laid on batten
fixed over the boarding.PREPARED BY : PROF. D.V.PATEL

ASBESTOS CEMENT SHEETS
• Asbestos cement is a mixture of
cement and powdered asbestos
then converted in to thin sheets
or tiles.
• Do no require any protective
coating and not decay or eaten
by insects , durable, light,
cheap and fire resistance that’s
why commonly used for
sloping roof.
• Big six and Trafford sheets are
commonly used , available in
2to 3cm. Length.
• While laying A.C. sheets ,
should be ensured that their
smooth surface is kept upwards
and end marked kept towards
the ridge ,not towards eaves.PREPARED BY : PROF. D.V.PATEL

SLATES ROOF COVERING
• Slates are is obtained from
sedimentary rocks of lime stone.
• Common size of slates vary
from 60cm * 35cm to 25cm*
12cm. And thickness from
1.6mm to 4.8mm.
• Available in grey, purple, red,
blue and black color
• It can be fixed by various method
such as fixed on the batten or
fixed on timber rafters, or laid on
wooden boarding or fixed on
roof framework.
• There are two methods of fixing
slates depending upon the
position of nail holes–
• Centre nailing and
• Head nailing

GALVANISED CORRUGATED IRON
SHEETS
• G. I. sheets are
manufactured like Big six
• A.C. sheets.
• The sheets are gal vanished
with zinc to prevent from
rusting and other weather
effect .
• Durable, fire resistant, light
in weight but transmit heat
orcold easily
• Very much as roof covering
for factories , workshops
etc.

SHEET METAL ROOF COVERING
• Copper sheets, lead sheets,
zinc sheets are some ex.
of this type of roof
covering.
• Copper and lead sheetsare
very costly
however zinc
sheetscan be used butnot
long lasting.
• Sheets may be 7.5cm
wide and 20cm long and
14 to 16 gauge thick.
• The ground work for
fixing of these sheets
more or less same asPREPARED BY : PROF. D.V.PATEL

TAR OR BITUMINOUS FELTS
Tar or bituminous is used
as covering material. It is
not a roof covering itself
but a sort of flexible
membrane which can be
laid to render the roof leak
proof.
Durable, impervious, non
porous, do not melt or
soften under heat, flexible.
But can not stand the
wear and tear traffic, do
not give good appearance,
do not provide a self
supporting structure . PREPARED BY : PROF. D.V.PATEL

GLASS COVERING
Mostly used on roofs
of industrial
buildings, factories etc
to admit light through
theroof.
It is not used these days
because of Very costly
covering, Difficult to
keep these surfaces clean
and water tight, etc.

Technical terms and types of roof coverings

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Technical terms and types of roof coverings