The Problem Statement:
🌳🛠️ The depletion of building resources like timber, bamboo, and thatch have progressively made the village house-builder’s jobs more and more difficult. Timber used to be the principal structural material while bamboo came in handy for almost everything. Shrinking forests have contributed to removing timber and bamboo from the reach of the poor. Even thatch has become scarce and the frequent repair requires for thatch roofs make them problematic. 😓🌿🚧
The Approach:
The above need was sought to be met through designing a low-cost house with an arched roof of hollow cylindrical clay tiles resting on a ring beam supported by brick pillars, while the non-supporting walls are made from non-erodible and rodent-proof mud walls using special techniques. This technique has been developed and propagated by Centre of Science for Villages (Wardha). 👷‍♂️🏠
Guna Vault Roof: “Guna” in Telugu, is a tapering, burnt clay pipe. The familiar semi-cylindrical pan tiles are obtained by splitting such pipes vertically into two. These “Guna” tapering pipes can be socketed into one another forming an arch over a suitably curved shuttering. A series of such arches make a barrel vault capable of withstanding considerable loads - up to 1 ton/m2. 🏗️🔩💪
The top of the roof is given a plaster finish. After joints are filled and topped with plaster, the roof becomes rigid and waterproof, doing totally without steel or timber. The cost of this roof works out to Rs. 20/sq.ft. 💰💧
It has the following advantages:
👉Air inside the hollow-tiled roof protects from heat and cold. A 10° temperature difference is observed in slab roof and Guna vault roof.
👉It has no under structure, yet can bear weight of 1000 kg/m2.
👉It is fabricated and ready for use within 3 days.
👉Requires no maintenance and has life span of more than 50 years.
👉It is not affected by rain, hail or wind.
👉Being light in weight (less than 12 kg/sq. ft). the vault roof is safe even in earthquakes.
👉Even if the mud walls collapse, the roof remains intact residing on pillars and beams.
After construction of brick pillars, ring beams and gable walls, the M.S. trusses are placed in position above the opposite pillars held with guy ropes and timber poles. Now GI pipes (12 mm dia., 10 nos.) are placed on the trusses in the MS rings provided at specific points. They are supported by gable walls at both ends. Guna pipes are now laid dry on this skeleton shuttering in a plug-socket manner, completing the roof ring by ring. Lime/cement mortar is now poured on the roof, trowelling it into the gaps and leaving the top rough to receive the finishing coat. Care is taken to remove the skeleton support within 12 hours to allow natural setting.