Where does the efficiency of roof design lie? In green architecture, it is rooted in how far we work with nature or go against it and then use technical solutions to make up for it. Incidentally, majority of the people cannot afford the costs of mitigating ecological problems created by our designs and silently suffer the house which is a heat trap or pay for maintenance costs of a multi-storey apartment block or clean a school that goes wet with every rain. Very few can pay for air-conditioning, but if the majority seek this solution, the city would suffer!
Roofs play a major role in the efficiency we are discussing about — be it in cracks, leakages, heat gain, activity space, structural costs or design aesthetics.
The roof has to be specifically designed to take and transfer the load to the walls or beams. As such, the stability of a structure is much dependent on its design. Simply stated, there are two ways by which the weight affects the constructed member: the factor that may bend the member, known as tension; and the factor that may crush the member, known as compression.
Wood, steel, reeds, thick stone section and such others which act like a beam are good at transferring tension loads. Arches, vaults and domes, along with other related masonry details like corbelling, take good care of compressive loads.
All roof options resolve how these two forces of tension and compression are balanced.
While professionals freshly calculate the design values for each roof case by case, where they are not involved, as is the majority, people simply do the roof by precedence. Most professional follow some default practice which they keep repeating, where the building owners have no clue at all.
Design options
Would we believe if we were told about a dozen types of roofs in Bangalore? The following list is amazing but true. Sloping thatch roof; sloping Mangalore tile roof (with or without ceiling tile); Hourdi block roofs (in slope & in curve); flat roof with stone slab; normal RCC roof (flat, sloping, curved); filler slabs in flat, slope or curve (wpc tiles, Mangalore tiles, cement blocks, clay hollow blocks etc as optional materials as fillers); arch panel roof; Madras terracing; wood plank roofs; vaults in RCC or masonry; masonry domes; corbelled roofs and sheet roofing (in varied materials). Including the variations, the list extends beyond two dozens! Each comes with its set of climatic comfort and carbon footprint; issues of execution and attractiveness; cost and benefit; problems and potentials; appropriateness and design style; and such other criteria. Incidentally, most of us do not explore all these options before deciding the final form of the building.
Options like thatch roofs could be totally out of race for an urban school, yet searching for the right fit would not only popularise some of the lesser known ideas, but also generate newer ideas.
(The writer is an architect working for eco-friendly designs and can be contacted at >varanashi@gmail.com)
