Roof of a building is the upper most protective covering provided over the building. Its objective is to protect the building from rain, heat, wind, snow etc.
The selection of type of roof depends upon the span, type of building, location, wind velocity, intensity of snow fall, heat insulation, lighting and ventilation etc.
The roofs can be classified into four categories:
- Pitched or sloped roofs
- Flat roofs
- Shelled roofs
- Domed roofs
For home construction, the first two types of roofs i.e. Pitched roofs and flat roofs are adopted whereas, the last two i.e. Shelled roofs and Domed roofs are used in Public buildings like recreation centres, libraries, theatres etc. Therefore, here we will discuss only about Pitched roofs and flat roofs.
1. Pitched or sloped roofs:
Roofs are termed as sloped or pitched, when their angle of inclination exceeds about 10o with the horizontal. Angle of slope is kept small if conditions of wind and rain are not severe and also snowfall is not likely to take place. As the conditions of wind, rain and snow fall become more and more critical, slope of the roof is increased proportionately. But slope is normally not allowed to exceed 60o.
This type of roof is the only roof adopted in hilly areas or areas subjected to extreme winds, rains and snow fall. Also this type of roof is commonly used for roofing large spanned structures like factory buildings, ware houses, workshops etc. in plane areas.
Advantages of Sloped roofs:
- In regions of heavy rainfall and snowfall, sloped roofs are most suitable as their drainage is very easy.
- Sloped roofs are much cheaper than flat roofs.
- Sloped roofs can be constructed in comparatively less time than flat roofs.
- They can be used over large spans.
- It gives better architectural appearance.
Disadvantages of Sloped roofs:
- Its construction and maintenance is not simple.
- It’s not easy to rectify the leakage problems in sloped roofs.
- Sloped roofs cannot be used for other activities.
2. Flat roofs:
The flat roof is such a roof, whose top finished surface has a slight slope to drain off rain water. The construction of flat roof is similar to that of upper floors except that the top surface is made slightly sloping and also they are given such a treatment that they do not leak even in heavy rains. Flat roofs may be constructed in R.C.C., Flagstone, bricks, tiles etc.
This roof is widely used in plane areas and in multi-storeyed buildings.
Advantages of Flat roofs:
- Its construction is easy and simple.
- The roof area can be used for roof gardening, playing and sleeping in hot season.
- In case of multi-storeyed buildings, flat roofs give better appearance than sloped roofs.
- It is easier to make flat roofs fire resistant.
- It has better insulating properties.
- Surface area to be covered in flat roofs is smaller than curved or sloped roofs.
Disadvantages of Flat roofs:
- Flat roofs are costlier than sloped ones.
- They develop cracks when their top surface is subjected to violent variations in temperature.
- In regions of heavy rainfall, flat roofs are not preferred as their drainage becomes difficult.
- It is difficult to trace and rectify the leakage.