Answer:
The foundation is part of the construction where the base of a building meets the ground. Foundation are usually placed below ground level because the surrounding ground provides
1. Stability
2. Protection against impact
3. Protection from the extremes of weather such as excessive rain or drought
Foundations are divided into 2 types
1. Natural foundation. This is the ground under earth the base of the building after the excavations are completed.
2. Artificial foundation. The structure that lies between the building and the natural foundation.
In order the design a safe, yet economical foundation for a building on a particular site, it is necessary to determination loads on the foundation which are:
1. Dead loads - which are the structure of the building including the wells, roofs, ceilings, fittings, plumbing, etc
2. Live loads which are the people living of working in the building together with the furniture, fitting and machines, etc.
3. Wind loads which are the impact on the roof and exterior walls of the building and transmitted down to the foundation.
The foundation is also determined from the type of soil which can be discovered through trial hole excavations.
The artificial foundation is to transfer the building loads to the ground and speeds the load evenly across it. This prevents settlement or building movement which might cause instability and endanger the occupants.
With the above facts in mind, the requirement for the foundation of a building are:
1. The foundation do not rest on made up or previously used ground. This is because the made up ground is non loading bearing. This will likely result in uneven settlement of the building, causing cracks or structural damage to it.
2. The subsoil on which the foundation of the building rests, is of consistent textile hand or weak spots can cause uneven settlement and lead to structural damages.
3. Should strip foundation be selected as the foundation of a building and this is common for low rise buildings, the walls of these buildings must be c?? on the strip foundation. This ensures that the bearing pressure on the foundation is evenly distributed.
4. The foundation are wide enough and deep enough to avoid soil movement that could cause instability. Depending on soil conditions, the maximum depth may be 900mm. Building regulations suggest the suitable minimum width for strip foundations. The concrete must be at least as thick as its projection from the base of the wall.
As shown in diagram above, the thickness D is recommended to be 150mm or more. D Should also be equal to P or more. P is the projection from the base of the wall to the side. This ensure the pressure of the building load is being distributed at an angle of 45% and covers the maximum area.
5. In situation where stepped foundation are being employed, a higher foundation projects ?? and meet a lower foundation for a minimum distance of 300mm or slopping ground.
This is to ensure that the foundation is strong enough to take on the building loads especially at the point where the foundation is 'stepped'.
Above flow chart summarizes the requirements for the foundation of a building and how to ?? at the right choice of a foundation.
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