Domes: stylish, inexpensive
When time-tested ideas get fogged, revalidating them demands fresh efforts. Take domed roofs for instance.
A simple question: besides the flat and sloped roofs, what roof types do we commonly see in historic buildings? The answer from a majority of us would be: domes. Until about 100 years ago when steel entered the construction industry followed by RCC applications, domes and vaults (long roofs semi-circular in shape) were among the most common approaches for large buildings all over the world. Even today, in areas where only mud is available as the local material, the smallest of houses also has domed roofs.
If masonry roof structures ruled the world for thousands of years, they cannot be invalid now just because RCC is in vogue today. When time-tested ideas get fogged, re-validating them demands fresh and new efforts. This is what Hassan Fathy, an Egyptian architect did, about 70 years ago, in re-discovering the Nubian methods of making brick domes and vaults. While designers had written off masonry domes as an obsolete idea, Fathy sought masons who knew about the dying art of building them and went ahead with the projects. In India, Auroville and ASTRA group at IISc. played a pivotal role in making them once again popular.
Built in short time
Natural semi-circular domes can be built in a short time without formwork using Nubian methods. The centre pint of the dome is marked on the ground where a pipe is pivoted, which could be rotated to ensure the designed distance and radius of each course. Bricks are applied with stabilised mud mortar and placed along the radius. Since they are guided by the pivoted radius rod, as the courses rise, dome shape automatically evolves. Being a curved surface, one face will have wider joints, which can be tightly wedged. The mortar should be paste-like with high water content, such that each brick gets stuck to the other. Thinner the bricks the better, because lesser the masonry block weight, lesser the downward thrust.
RCC domes are equally well possible, but will cost more and have greater construction complications; hence the alternative modes of dome construction could be considered. Corbelling is another option to get either the vault or the dome. Here every subsequent course of brick projects out of the previous by few inches, resulting in a circular form, finally to close in on the top. The oldest surviving corbelled dome found in Greece is now over 3,500 years old!
In recent times, masonry domes have resurfaced with hundreds of buildings already built around us. They work out cheaper, appear unique and above all highlight the feasibility of the alternative ideas. Of course, domes have never been a regular part of our traditional residential architecture, though many masonry domes and vaults are found in traditional public buildings designed for a cultural image or for large gatherings. Anyway, in many parts of India, local masonry materials still being available and skilled labour possible, masonry constructions continue as a viable option.