In this presentation, I have explained pitched roofs in details as follows: 1. external parts of pitched roofs 2. internal parts of pitched roofs 3. types of pitched roofs and their suitability

1. 2.4. Pitched Roofs
Rohan Dasgupta
Mod. 2: Components and Services of a Building

2. Pitched roof is a roof that slopes downwards from a ridge (the highest point of a roof).
Image courtesy: https://www.homedit.com/classic-gable-roof-style/house-of-hunting-gable-roof-arkitema-architects/

3. Pitched roofs may slope downwards on one side or both sides.
Image courtesy:https://www.houzz.in/photos/green-built-modern-phvw-vp~4360777 Image courtesy: https://www.homedit.com/classic-gable-roof-style/house-of-hunting-gable-roof-arkitema-architects/

4. Any roof having a slope less than 10° is called as a flat roof.
However, the general slope of pitched roof ranges from 1:40 to 1:80.
Pitch of a roof = vertical rise / horizontal span
Image courtesy: https://www.homedit.com/classic-gable-roof-style/house-of-hunting-gable-roof-arkitema-architects/
vertical rise
horizontal span

5. External Parts of a Pitched Roof
Image courtesy: https://en.wikipedia.org/wiki/Roof#/media/File:Roof_diagram.jpg

6. Internal Parts of a Pitched Roof

7. (a) Single roofs
1. Lean to roof (verendah roof)
2. Couple roof
3. Couple close roof
4. Collar beam roof or collar tie roof
(b) Double or purlin roofs
TYPES OF PITCHED ROOFS
(c) Triple membered or framed or trussed roofs
1. King post roof truss
2. Queen post roof truss
3. Combination of king post and queen post truss
4. Mansard roof truss
5. Truncated roof truss
6. Bel-fast roof truss or latticed roof truss
7. Composite roof truss
8. Steel sloping roof trusses

8. Single Roof:
If the span of roof is less than 5 m the following types of single roofs are used: (i) Lean to roofs (ii) Coupled roofs, (iii)
Coupled-close roof, (iv) Collar beam roof
In all these roofs rafters placed at 600 mm to 800 mm spacing are main members taking load of the roof. Battens run over
the rafters to support tiles.
This is provided when wall on one side is higher than the other.
This type of roof is suitable for out-houses and sheds attached to the main building.

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

11. Trussed Roof:
If span is more, a frame work of slender members are used to support sloping roofs.
These frames are known as trusses.
A number of trusses may be placed lengthwise to get wall free longer halls.
Purlins are provided over the trusses which in turn support roof sheets.
For spans up to 9 m wooden trusses may be used but for larger spans steel trusses are a must.
In case of wooden trusses suitable carpentry joints are made to connect various members at a joint. Bolts and straps are
also used.
In case of steel trusses joints are made using gusset plates and by providing bolts or rivets or welding. Depending upon the
span, trusses of different shapes are used. End of trusses are supported on walls or on column.

13. Thank you
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- Rohan Dasgupta
B.E. (Civil), M.E. (Structural), Ph.D. (pursuing…)
Navi Mumbai, Maharashtra, India
+91 9967569336