Some useful tips for building foundation in black cotton soil
In order to restrict the load on the soil to 5.5 tonnes/sqr.m, the lowest depth of foundation should have been minimum 1.5m.
The reinforced concrete ties or bands are arranged all around the main walls of the building. The R.C.C ties or bands with depth 10cm to 15cm should be set up at plinth level, lintel level and eaves level. For flat roof, R.C.C slab itself functions as a tie and for that reason, it is not necessary to arrange additional band adjacent to the roof in such cases.
If the deepness of the black cotton soil at a specified site is only 1 to 1.5m, the complete black cotton soil over the hard bed should have been entirely detached and the foundation may be placed on the hard bed below.
If the swelling of soil is directly connected with the foundation material, maximum damage is happened. Therefore, it is essential to take proper measure to get rid of the direct contact of black cotton soil with masonry work underneath ground level.
It should be done by creating wider trenches for foundation and filling spaces on the either side of the foundation masonry through sand or moorum.
The bed of foundation trench should be formed as firm or hard by ramming it well. On the rammed bed a 30cm layer of good hard moorum should be stretched in layers of 15cm, each layer should be drenched well with water and rammed prior to place the next layer.
On this layer either stone or sand bed should have been arranged to the required height to set the foundation concrete bed block upon it.
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