Coconut shells Filler slab roofs are basically solid reinforced concrete slabs-Dr.K.Govindaraju

Cocunut shell filler slab roof of SEVAI centre

Energy efficient SEVAI School building

The quest for cost-effective, innovative and environment-friendly housing has focussed on the appropriate use of locally available materials, skill and technology without compromising on the quality and life of the structure. Finding a substitute for the heavy roof slab has been one of the major challenges for structural engineers, mainly because of the difficulty in managing the heavy stress forces. After years of research and development, engineers came up with the filler slab as an alternative even with Coconuts shells as roofing slabs. Despite initial hesitation in accepting the new technology, the filler slab has today become popular as a practical low-cost alternative. Coconut shells Filler slab roofs are basically solid reinforced concrete slabs with partial replacement of concrete by a filler material that is cheaper and lighter. In a roof slab, the upper portion bears compressive loads whereas the lower is subjected to tensile load. While bricks or concrete absorb the compressive loads on the upper portion of the slab, tensile strength is imparted by the framework of steel rods on the lower side. The filler slab is a mechanism to replace the concrete in the tension zone. The filler material, thus, is not a structural part of the slab. By reducing the quantity and weight of material, the roof become less expensive, yet retains the strength of the conventional slab. The most popular filler material is the roofing tile. Mangalore tiles are placed between steel ribs and concrete is poured into the gap to make a filler slab. The structure requires less steel and cement and it is also a good heat insulator. The uppermost part of a constructed structure is called roof, provided to protect the building from rain, wind, snow, sun etc. It protects human beings, animals and also materials kept inside building.  The roof should be strong, stable, weather proof and safe against fire and disaster. One way to make a boring and expensive concrete slab lighter and cheaper is to use a 'Filler Slab'. A filler slab is where we replace a portion of concrete in the 'tension' zone of the slab with inexpensive lightweight filler materials such as coconut shells, glass bottles or any other creative material we can think of. In a simply supported RCC slab, the upper part of the slab is in compression while the lower portion of the slab experiences tensile forces. The steel reinforcement in such a slab is in the lower part to counter the tensile forces but the concrete (which is weak in tension) in that zone is mostly redundant except for a small portion required to hold and protect the steel rods. This redundant concrete can be replaced with a cheaper filler material. By choosing the filler material judiciously, we could save about 30-35% of concrete compared to a traditional RCC slab. A light weight filler material also reduces the dead load hence less steel reinforcement is required. In all we may expect to save about 25% of the cost. A filler slab with two stacked clay tiles as shown in the sketch above also increases the thermal insulation of the slab.  A filler slab can be used to Reduce use of energy intensive materials,. Save on construction cost, Increase thermal comfort, and create an interesting look. Coconut Shell roofs are made to meet functional and architectural requirements. -Govin