EVERY HOUSE has four walls, floor and a roof, all acting as protective shields against nature and harmful elements. Good architecture is the play of all the six planes to create forms that are interesting and appealing. Roof is an essential element of the six planes and is as important an element as the other five planes.
Michelangelo's painting on the ceiling in the "Sistine Chapel" is a classic example of how important roofing has been. But of late it has not been explored well. With ample options available, the choice of the roof depends on the cost factor, the climate and the kind of aesthetics one is looking at. For a hot and humid climate like that of India, a proper roofing system demands to have a good insulation from heat and it can lend a strong character to any building for the aesthetics part of the roofing choice.
Reinforced Cement Concrete (RCC) has become the most preferred material for all structural works in building and for roofing as well. RCC flat roofs are the most commonly used system in south-eastern India. Due to its simple form, and the ease of execution, the flat slabs are easy to fabricate and can be quickly cast as well. The flat slabs usually rest on roof beams and load bearing walls. Their thickness varies from 4" to 5" depending upon the size of the room.
Flat slabs can be classified as one-way slabs and the two-way slabs. One-way slabs, as the name suggests, can be used for narrow rooms with a maximum width of 10' to 12' and have steel reinforcement designed to be spanned one way only making them more economical.
On the other hand, two-way slab can be spanned both ways. The steel usage is more but large column-free rooms (16' x 20', 18' x 18' etc) are possible. Other means of achieving large span roof slab is to provide grid slabs or coffered slabs. In such roofing systems, large span halls (say 30' x 70') are possible.
The spatial feel inside a room can be well articulated by the height of the roof plane, its shape and its slope. The Structural Engineering Research Centre (SERC) and the IIT have developed cost effective RCC funicular shell roofing, and brick funicular shell roofing, which have a hemi-cylindrical shape giving a sense of continuity and newness to a space as against the conventional flat roofs. These brick funicular shell-roofing systems cost 70 per cent of a conventional RCC slab. Parabolic or hyper parabolic shell roofs are exciting roof forms but can be executed by a good engineering team with the architects supervision. These shell roofs can be traced back to the medieval domes and vaults, which were worked on in a detailed manner with painters and artwork .
Skylighting an internal space can also be done by puncturing the roof slab. This puncture can be sealed with fibre-glass or poly carbon sheets or wired glass. This proves vital in continuous development zones like Triplicane, Mylapore, George Town and Purusawalkam.
Sloped roofs are the next option. They have become a part of the south Indian culture through the British contribution during their reign.
Improvising on the sloped roof system, Mangalore tile on the top with a combination of decorative handmade tiles in the inside laid over MS flat, this technique helps achieve a roof cover that breathes and hence keeps the room cool.
Thinking of some futuristic material, aluminium or metal sheet roofing over metal trusses can be tried for some modern and bold roofing system just as in the Ford and Hyundai factory.
The author is the chief architect of Murali Architects, Chennai