Timber roofs

Timber Roofs

1. TIMBER ROOF TRUSSES

2. Pitched Roof- Basic elements

3. Pitched Roof- Basic elements

4. TIMBER PITCHED/SLOPED ROOFS
1. SINGLE ROOFS
•Lean-to-roof
•Couple roof
•Couple-close roof
•Collar-beam roof or collar tie
•Collar and scissors roof
2. DOUBLE OR PURLINROOFS
3. TRUSSED ROOFS
•King-post roof Truss
•Queen-post roof Truss
•Mansard roof Truss
•Truncated roof Truss
•Belfast roof Truss
•Composite roof Trusses
•Steel sloping roof Trusses

5. SINGLE ROOFS
1.LEAN-TO-ROOF
•This is the simplest form of a
pitched roof and it is known as
the pent roof or aisle roof.
•One wall is carried up higher than
the other one to give necessary
slope to the roof.
•The rafters are suitably secured
on the wall plates and eaves
boards, battens and roof covering
are provided.
•A lean to roof is generally used
for sheds, out-houses attached to
main buildings, verandahs,etc.
•It is suitable for a maximum span
of 2.40m.

6. SINGLE ROOFS
COUPLE ROOF
•The roof is formed by couple or pair of rafters which slope to both the
sides of the ridge of the roof.
•The upper ends of each pair of rafter is nailed to a common ridge piece
and their lower ends are notched and nailed to the wooden wall plates
embedded in the masonry on the top of the outer walls.
•Not very favourable as it as the tendency to spread out at the feet and
thrust out the walls supporting the wall plates.
•Suitable for spans upto about 3.60m.

7. SINGLE ROOFS
COUPLE CLOSE ROOF
•A couple close roof is similar to the couple roof, except that the ends of
the couple of common rafters is connected by horizontal member called
tie beam, to prevent the rafters from spreading and thrusting out of the
wall.
•The tie beam may be wooden member or a steel rod.
•The connection between wooden tie and feet of rafters is obtained by
dove tail halved joint.

8. SINGLE ROOFS
COUPLE CLOSE ROOF
•For inferior work, the ties may just be spiked to the rafters.
•There is one tie beam for each pair of rafters.
•These tie beams can also be used as ceiling joists when required.
•Span upto 4.20m.
•For increased span or for greater loads, the rafters may have tendency to
sag in the middle.
•This can be checked by providing a central vertical rod, called King rod or
King bolt which connects the ridge piece and the tie beam.

9. SINGLE ROOFS
COLLAR BEAM ROOF
•When the span increases, the rafters of the couple close roof have the
tendency to bend.
•This is avoided by raising the tie beam and fixing it at one third to one
half of the vertical height from wall plate to the ridge. This raised beam is
known as the collar beam.
•Span upto 5m.
•A collar beam provides roof greater height of the room.

10. SINGLE ROOFS

11. SINGLE ROOFS
COLLAR AND SCISSORS ROOF
•It is similar to the collar roof, except that two collar beams. Crossing each
other to have an appearance of scissors is provided.

12. TRUSSED ROOFS
KING – POST TRUSS
Span varying from 5m to 8m.

13. TRUSSED ROOFS
QUEEN – POST TRUSS
Span varying from 5m to 8m.

14. ROOF COVERING MATERIALS
THATCH:
•Very light roof covering
•Combustible, absorbs moisture rapidly and is easily liable to decay.
•Unstable against high winds.
•A bed of matting is prepared to receive the thatch and in order to drain
the roof easily, a pitch of 45 degrees is kept.
•The thatch is used in rural areas because it is the cheapest form of roof
covering and it is simple in construction.

15. ROOF COVERING MATERIALS

16. ROOF COVERING MATERIALS
ORDINARY HALF ROUND COUNTRY TILES:
•These are used for cheap buildings.
•If tiles are laid in two layers, the roof is known as a double-tiled roof.
•An overlap of at least 80mm should be provided when these tiles are
used.
•These tiles are liable to break easily and hence they require frequent
replacement.

17. ROOF COVERING MATERIALS
SHINGLES:
•The wood shingles are obtained from the well-seasoned timber with
lengths varying from 300mm to 380mm and widths varying from 60mm
to 250mm.
•They are laid in a similar fashion as tiles and slates, and this roof covering
is found to be useful especially in hilly areas where the wood is easily and
cheaply available.

18. ROOF COVERING MATERIALS
Eternit slates:
•These are fire-resisting, light and cool.
•They are not easily affected by weather.
•Abought eight slates are required for covering one square metre of roof
area.
•The eternit slates are generally available in three colours-grey, black and
red.

19. ROOF COVERING MATERIALS
Corrugated galvanized iron sheets:
•They are prepared by pressing flat wrought-iron plates between rollers
with grooves or teeth and they are galvanized with a coat of zinc.
•These sheets are commonly known as the G.I.Sheets.

20. ROOF COVERING MATERIALS
Asbestos cement corrugated sheets:
•The cement is mixed with about 15% of asbestos fibres and the paste so
formed is pressed under rollers with grooves or teeth.
•Thus A.C. sheets have series of waves or corrugations and are used for
factories, workshops, gargares, big halls, etc.
•They do not require any protective paint and cannot be eaten away by the
vermins.

21. TIMBER ROOF TRUSSES