Random rubble masonry is extensively used as foundation at places where stones are readily available. An 18” (45 cm) foundation base is adequate for most soils and single or double storey buildings. Depth and size may vary with the addition of number of floors. In case of weak soil, the trench can be widened (50-60cm) and the bottom can be laid with concrete (1:2:4) followed by a 30-35cm wall.
For the foundation, a trench 50 cm wide is dug and laid with rubble. It can be dry masonry or mud mortar. For higher masonry walls, cement mortar (1:10) can be used. (It is always wise to pile the excavated soil between the plinth walls to prevent cost of future filling).
Proper joints (dovetail) must be provided for stronger bonds as in the case of any other masonry works. Stones must be large in size and the gaps between stones must be filled with smaller stones for proper bonding and stability. Care must be taken to ensure bonding of stones along the length of the wall. Bamboo in lime concrete can be used for foundations, especially in the sandy areas along the sea coast. It is resistant to sea water. It remains intact whereas other foundations will crack with shifting sands. For places where stones and bricks are not available, foundation for mud walls can be of moist soil with layers of split bamboo reinforcement inserted.