How to make the design of a Foundation
Foundation is the portion of structure underneath plinth level up to the soil. It is directly connected with soil and it transfers the load of super structure to soil. Normally, it is located under the ground level.
If some portion of foundation is situated over ground level, it is also enveloped with earth filling. This part of structure is not in touch with air, light etc, It is considered as the concealed part of the structure.
Depth of Foundation: Depth of foundation is based on the following points-
1. Sufficient bearing capacity should exist
2. Depth of shrinkage and swelling for of clay soils, because of change in climate that may lead to appreciable movements.
3. Depth of frost penetration for fine sand and silt.
4. Chances of availability of excavation
5. Depth of ground water table
6. Practical lowest depth of foundation should not be under 50 cm. to facilitate subtraction of top soil and deviations in ground level.
7. So, the desired depth of foundation should vary from 1.00 meter to 1.5 meter from original ground level.
Footing: Footing belongs to a structure that is built up in brick work, masonry or concrete under the base of a wall or column for dispersing the load over a extended area.
Width of Foundation/Footings
The width of footings is based on the structural design. For light loaded buildings like houses, flats, school buildings etc which do not contain over two stories, the width of foundation is provided below :-
1. The width of footing should not be under 75 cm for one brick thick wall.
2. The width of footing should not be under 1 meter for one and half brick wall.
Various methods in Foundation Work: The following methods are involved in the foundation works -
1. Excavation of earth work in trenches for foundation.
2. Work out cement concrete.
3. Set the footing for raft or column construction.
4. Arrange Anti termite treatment.
5. Set Brick work up to plinth level.
6. Set Damp proof course on the walls.
7. Refilling of earth around the walls
8. Refilling of earth in the building portion up to the desired height as per plinth level.