Roofing practices

Evolution of roofs.

20bgh-greensens_20_2116785eAsk any one with experience in construction about formwork and shuttering, they are likely to say how it is time consuming, expensive and often a headache. More so in urban centres where it is difficult to get skilled people who can erect the formwork to precision. To cast a flat concrete roof, we need to create the flat surface in advance, complete with supports and capacity to take the load of the roof. If it is complicated with levels, curves, varied thicknesses, different geometries and such others, that’s then a prescription for errors.

Incidentally, our traditional buildings escaped this burden – most often they lifted the wooden beams and masonry materials one by one to assemble at roof level. Flat or sloping roof profiles made no difference to this simple technology. Of course, they would have erected temporary supports for some kind of forms like domes, but most common buildings were built without formwork.

Would it not be wonderful to build roofs without or with minimum formwork? After all, what we finally need is the final roof and not this temporary roof support. This thought led our modern engineers to discover methods that would use components made ready on floor to be lifted up. The initial ideas explored pre-cast beams to replace wood and then place smaller segments of roof elements made in site, which led to the arch panel roof which uses no formwork at all. Everything is assembled on top.

Challenge

Considering they are multiple elements, ensuring a water-proof surface has been a challenge in this technique. To that end, some prior experience is required to do the arch panel roofs. What if the roofs are homogenous? We can avoid many irritants like cracking joints, water proofing the roof and such others. The scientists at Indian Institute of Science, mainly Dr. Jagadish and Dr. Reddy, focused on the traditionally popular domes and vaults, to know how to re-introduce them as a cost cutting measure.

The main inspiration came from roof forms in historical buildings, primarily revolving around domes and vaults, i.e. curved roof forms. Architect Hassan Fathy had demonstrated an ancient technique to build them without any formwork and slowly the idea percolated to India also. These ideas are generally cheaper, appear more unique and make the job much simpler. Accordingly, we see them at the Development Alternatives building in Delhi and the building centre in Auroville. Slowly many architects practising alternative design ideas took these ideas and tried spreading it.

While the pre-condition for the research was to reduce cement joints, it also led to newer architectural forms and challenges. Coupled with further alternative materials like stabilised mud block, the roofs without shuttering met the expectations of many clients.

These alternative roofs create larger volumes inside, in case of hot regions, increasing the indoor thermal comfort. Mostly they are made of natural materials, thus reducing the embodied energy of the structure as a whole, becoming green.

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Posted on September 20, 2014, in concepts, fundamentals and tagged , , . Bookmark the permalink. Leave a comment.

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