Roofing
1
ROOFS
 It is constructed to protect the building
from weather (rain, wind, heat, snow, etc)
 Roof is the uppermost part of the building
REQUIREMENTS OF A ROOF
 Durable against various natural agencies
 Adequate thermal insulation
 Water proof
 Fire resistant
 Sound insulation
 Good drainage arrangement
CLASSIFICATION OF ROOFS
1. Pitched or sloping
Single roof,
2. Double roof,
3. Trussed roof.
2. Flat or terraced
1. R.C.C roof,
2. Madras terrace roof.
3. Curved
1. Shell roof,
2. Dome roof.
1.
PITCHED ROOFS
 These roofs have sloping top surface
 Suitable in those areas where rainfall/snowfall is very heavy
 Span: clear distance between the supports of beams,
roofs or truss
 Rise: vertical distance between the top of the ridge
and the wall plate
 Pitch: inclination of sides of a roof to the horizontal
 Ridge: an apex line of a sloping roof
PITCHED ROOFS
TERMS - ROOF
 Gable: triangular upper part of a wall formed at the
end of a pitched roof
 Purlin: horizontal member placed over the principal
rafters to support the roof membrane.
TERMS - ROOF
TYPES OF PITCHED ROOFS
 Single roofs
 Double or purlin roofs
 Trussed roof
King post truss
Queen post truss
Mansard truss
Bel fast truss
Steel truss
Composite truss
SINGLE ROOF: 1.LEAN TO-ROOFS
 Rafters slope to one side only.
 Upper ends- rafters are fixed by
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
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nails to the wooden plates.
Lower ends- rafters are
notched & nailed to the
wooden post plate.
Battens are placed and fixed
over rafters.
Roof covering materials.
Spans upto 2.5 m.
2.COUPLE ROOF
 Pair of rafters
 Slopes to both sides
 Upper ends- nailed to
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common ridge piece
Lower ends- notched &
nailed to wooden wall
plates.
Battens are fixed
Roof covering materials
Span upto 3.60 m.
3.COUPLE CLOSE ROOF
 Tie beam
 Prevent from
spreading
 Spans upto
4.20 m.
COLLAR BEAM ROOF
 Span increase or heavy
load- leads to bend
 Prevent by raising the tie
beam
 1/3rd to ½ of the vertical
ht. from wall plate to the
ridge.
 Spans upto 5m
DOUBLE OR PURLIN ROOFS
 Rafters- rest at the ends
on wall
 Purlins- intermediate
supports
 Spans upto 5.5 m.
TRUSSED ROOF
A
number
of
straight members
connected in the
shape of triangle
and forming a frame
is known as truss.
 Truss are provided
at regular interval of
about 3m along the
length.
 Used for the span
more than 5m.
KING-POST TRUSS
 King post- central
post
 Struts- inclined
members
 Principal rafterssupport the purlins
 Spans- 5 to 8 m.
QUEEN-POST TRUSS
 2 vertical posts
 Straining beam
 2 struts
 Straining sill
 Spans- 8 to 12 m.
MANSARD TRUSS
 Combination of king
& queen post trusses.
 Upper portion- king
post truss
 Lower portionqueen post truss.
 Upper pitch- 30 to 40
degree
 Lower pitch- 60 to 70
degree.
BELFAST TRUSS/ BOW STRING
TRUSS
 Thin sections of timber
 Top chord – curved
 30 m span – if roof
covering is light
 Rise not more than 1/8th
of the span
STEEL
TRUSSES
KING-POST STEEL TRUSS
COMPOUND FINK & COMPOUND HOWE’S
STEEL TRUSS
ADVANTAGE:
 stronger than wooden truss
 Very large span (5m to 30m)
 Easy to construct
 Fire-proof
 More rigid
 Permanent
 More economical
STEEL TRUSSES…..Cont 1
DISADVANTAGE:
 Likely to get rusted
 Need anti corrosive paints.
 Periodical maintenance
required.
USES:
 Building with large span
 Building with no intermediate
columns.
 Place of heavy rainfall of snow
fall.
COMPOSITE TRUSS
 Timber and steel
 Tension
members – steel
 Compression
members –
timber
 Light and
economical
FLAT ROOFS
 It is one which is either horizontal or horizontal with
slope less than 10°.
TYPES OF FLAT ROOFS:
 Madras terrace roofs
 Reinforced cement concrete slab roof
MADRAS TERRACE ROOF
MADRAS TERRACE ROOF
REINFORCED CEMENT CONCRETE
ROOF
 Easy to cast
 Very smooth surface
 Length / width > 2 – one way
 Length / width < 2 – two way
CURVED ROOFS
 Modification of pitched roof and are frequently
employed in modern age to cover large areas.
 Useful for assembly halls, recreation centres, factories,
monumental works
 Pleasing appearance
 Types
 Shell roofs
 Domes
NORTH LIGHT SHELL ROOF
 Mostly used in
 Factories
 Work shops
 Where good day light id
desired
BARREL VAULT SHELL ROOF
 Long multiple cylindrical shell
 Feather edge beams
 Where day-lighting is not must
DOMES
 Semi-elliptical or semi-
spherical
 Uniform or varying thickness
 Brick, stone, steel, wood,
concrete or tile