Building house at flood prone site: Things to keep in mind

After the recent floods that unleashed unparalleled devastation across Kerala experts have been pointing out aspects that can help houses withstand natural calamities like floods or storm.

Sreekant Pangapadu, an engineer with the PG Group of Designs in Kanjirappally, lays down a few instructions to be followed while constructing houses, especially in the flood prone areas.

Before purchasing plots to construct houses, a soil test should be strictly conducted. It would reveal the capacity of the soil in the plot to absorb water. Plots where puddles are formed easily should be avoided.

Do not cut the trees that stand on the purchased plot. If houses are constructed by filling small rivulets or streams with sand, chances of the foundation of the house to get sunk are high. Experts warn against building houses by hindering the natural flow of water. This would help to avoid extensive damage to the house during floods.

It is dangerous to build houses by levelling sloped lands by removing soil in huge amounts. During monsoon, the water seeps into the soil above and may lead to soil erosion or landslides.

Houses should be constructed only at a safe distance from the regulation zone of the rivers. New houses should be built at a distance farther than the level where the rivers changed its course during the recent floods.

A trial pit should be dug before beginning the construction, and seek expert advice from an engineer regarding the appropriate kind of foundation that would suit the soil in the plot.

Do not fill the small streams and rivulets that flow through near the houses or plots. The paving tiles prevent the soil from absorbing water properly. The rain water which flows out of the plot may increase the severity of floods. It is the water which gets seeped into the soil that keeps the wells always filled.

Proper waste disposal measures should be included in the plot as soon as the construction of the house is over. Tonnes of waste materials dumped back into the land by the rivers after the flood should be a lesson for people against polluting water resources.

In flood prone areas, houses should be built on a raised column or plinth beam foundation. The space below the house should be left open to facilitate the natural flow of water.

Low weight houses can be built on concrete pillars on moderate budget. Besides, houses built this way could withstand earthquakes and floods.

Experts say that the foundation of the concrete buildings should be built with PCC concrete and filling the top of it using hard rock chips mixed with cement. RR foundation can prevent, to a certain extent, moisture getting trapped on the foundation. In such cases, the foundation should be built on a certain height as well.

The concrete corner pillars in single-storey houses would be effective against cracks from appearing on the walls after a flood.

1:6/1:5 ratio should be strictly followed in the building of walls. PCC securing in 1:3:6 ratio and 2 inches width should be done around the foundation to prevent moisture from getting seeped into it.

Enough drainage facilities or slopes should be made for the water to flow out from the plot. It shouldn’t, however, block the public drainage system on the roads.

Concrete walls, and not hard rock structures, should be strictly built when cellar floor is built.

The DPC belt over the foundation should be built by making beams of 15 cms thick using iron rods. Good quality concrete in 1:1.5:3 ratios should be used to plaster it.

The plastering of the exteriors and shades should be done on a ratio of 1:4.

It is important to understand that the land or plot where cases of soil erosion or landslides have been reported are totally unfit to build houses or buildings.