Many of us may not be familiar with the term Chajja. ‘Chajja’ is the projected element just above the window, which shades the opening, stops rain from entering the room and reduces sky glare while looking out of the room. It is also known as “Sun-Shade” that is a sloping or horizontal structural overhang, usually provided for protection from sun and rain or for architectural considerations at lintel level. Previously a small cornice band would appear above the void, acting as a drip mould, directing the water flowing down the surface away from window. Creating shade for the whole wall is among the early knowledge people picked up while designing for the climate. Initially achieved through simple ideas such as projected roofs, closely placed dense housing, deep verandahs, planting trees and such others, slowly led to windows set in thick walls, projected ‘jharokhas’ and roof stone extensions. Traditionally, designs had deep roof eaves such that sunlight and rain would not penetrate deep into verandahs, porches, porticos, entrance, ‘mukha mantapas’, balconies and walls facing south and west.
Chajjas are normally 2–5 feet in length and 2 feet wide Chajjas is an essential part of the structure. Chajjas are mainly used for protection against elemental forces like the Sun and rains. Chajjas are mainly made of cement concrete, wood, fibers sheet-asbestos materials or from composite material etc. according to the requirement for the structure. Traditionally, most regions of India did not have the projection, nowadays called as concrete chajja. The sloping roof overhang was so deep; it would cover up the wall and window opening. Alternately, there would be a wooden bracket supporting the sloping sunshade over the windows. In case of flat roofs in hot arid regions, small stone slabs or sometimes an ornate window design as a box can be seen. The formal concrete slab projection as chajja appears to be a post-independence phenomenon, further popularised by PWD norms. Irrespective of cardinal directions, sun movement patterns, degree of shading required, type of building or any such criteria, we have been adding this concrete slab over the window everywhere. Most often, we do not know how effective this shading device has been.
Importance of Chajja
- Usually protects from external sunlight.
- Also protects from rainwater entering into the building.
- It also serves as aesthetic decoration with little design on it from architectural point of view.
- Windows-Chajja will not let water drip from above and soak the woods of windows. Otherwise the wood will absorb water and expand.
- Can be used as a support for AC.
Are Chajjas necessary?
Yes it is necessary. The first and the most important reason for making a chajja are to restrict the direct entry of rainwater. It decreases the amount of direct sunlight entering in the room. In some cases chajja also has been proven good for security purpose. Many engineers and architects also suggest constructing an outward projected frame around the window to stop the entry of rainwater from the sides of window. It provides a good aesthetic to the structure. Chajja protects building from sun and rain. Few people avoid chajja for elevation purpose. But it is not correct, At least you should not avoid chajja at south and west sides, which will get harsher sun exposure. In my opinion chajja is must for an opening in the building, to protect it from sun rays and rain.