Foundations are the mainstay of house construction as the stability and the performance of the structure above is dependent on it. The main design parameters for consideration in this respect are the depth and width of the foundation. Whereas depth of foundation is a function of the ‘Safe Bearing Capacity’ (SBC) of soil at a specific depth below ground level, the width is a function of the total loads of walls, slabs, finishing etc coming from the main structure.
It would be observed that design and construction of foundations has to be carried out carefully and there should be no laxity in this regard. If the following precautions are taken, a good foundation can be provided for the house.
Precautions
- There should be no trees or their roots near the area where foundations are to be provided.
- Foundations on natural drains of water should be avoided.
- The depth and width of foundations in bricks and/or concrete should be designed properly.
- The foundation surface should be watered and left open for some time and finally compacted either by hand compactor or rollers.
- Anti termite treatment should essentially be done in a proper and prescribed manner.
- Proper shuttering should be provided on the side walls of foundations to prevent soil caving.
- It should be ascertained that the foundations are laid in an absolutely straight line.
- Brick should be properly soaked in water before use. Similarly stones should be washed before use.
- The base concrete to be provided should be 7.5 cm to 15 cm (3″ to 6″) more on either side of the foundation design width.
- The base concrete should also be cured and rammed properly before commencement of work either for brick/stone foundation or for foundations in concrete
- The reinforcement bars to be provided for seismic strengthening should be properly embedded in the foundation as per directions.
- The foundations should be constructed in an absolutely vertical manner.
- The steel reinforcement for foundations in concrete should be provided as per design and placed with a proper cover.
- Proper cover to the reinforcement can be provided by placing cover blocks on base concrete. These can be made out of wood or concrete etc, say of size 2.5×2.5×2.5 cm (1″x1″x1″) or as may be required.
- Proper curing of RCC work in foundations should be carried in order to obtain the required strength.
- The entire depth of foundation should be at the same level to prevent differential settlement. Engineers advice should however be taken in this regard.
- Foundations should also be provided for half brick walls although they can be at a lesser depth and of lesser width.
- A cement mortar/concrete course, say of about 45 cm width, should be provided all along the outer side of the house at ground level. This is known as plinth protection course and prevents ground water from entering the foundations.
- Damp Proof Course (DPC) should be laid properly and its top surface should be at the same level all along the foundation walls.
Conclusion
Providing a good and appropriate foundation for the house is a key to safe construction. Accordingly, it has to be seen that the soil on which the foundation is resting has a good SBC and has the capacity of taking the load of the structure over it. Soil testing is recommended in this regard.
Another area of importance is the type of foundation to be provided for the house. If need be, the advice of a Civil Engineer/foundation expert can be taken who can provide a structurally safe and economical way to provide/construct the foundation.
A good and robust foundation is the first step towards providing structural safety to the house.