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Foundation is the firm concrete base on which the entire building rest on. It’s the lowest and supportive layer of a structure (Wikipedia).
Factors to Consider before even starting the design of a house, you should consider the factors below;
- Type of ground; is it a swampy or dry ground?
- Type of soil; is it loose sandy, firm or deep black cotton?
- The type of building; is it a low level house, or a multistory building?
- The climate of an area, eg area prone to floods.
It’s important that you involve the services of a qualified and experienced person to check the ground for you so as to determine the type of foundation you will put. Let’s look at the four types of foundation
Strip foundation-This is the most common type, it is mainly used where you have strong soil base and non-waterlogged areas. Most low level or buildings with few floors are constructed with this type of foundation. It supports line of loads either due to load bearing wall, or where a line of columns are so close that that individual column bases will impossible to have.
The depth and width of the foundation trench will depends on the structural engineers recommendation, the depth of your foundation could be from 600mm to 1200mm mostly for small scale buildings. The main reason for excavating foundation trench is to establish a firm ground level on which the concrete will settle on and distribute the loads of building evenly to the ground. The structural engineer will determine the thickness of concrete to be laid, otherwise, for low level house bungalow, 150mm (6 inches) of concrete thickness is accepted.
Pad foundation-This is where isolated columns are concreted from the foundation to carry a slab at the top of the ground. This is mostly used when you want to make use of under of a building as parking area est. These columns are thus isolated and their foundations are referred to as pad.
Raft foundation-This is where you have reinforced concrete spread on the entire area of the building, meaning the entire house rest on the reinforced raft concrete bed(foundation). It is mainly used in areas where the soil is sandy or loose, with low bearing capacity. You spend more on this than the other previous two most of the time. It is also recommended in waterlogged areas but with buildings of less storeys.This type of foundation allows the building to “float” on the ground, the load on the raft foundation is evenly spread on the entire foundation.
It has a ground beam which shuts out from the foundation base and is also attached to the ground floor slab to form a network of concrete embedded round the building space. The ground beam is usually from 600mm to 1200mm for low buildings.
Pile foundation.The most expensive and the strongest type of foundation, this requires specialist engineering to do. The soil are bored deep down the earth and filled with concrete to be able to support loads of multistory building on top. Most skyscrapers are constructed with this type OF foundation,a waterlogged area of high building may also require this.
It is the costliest hence it is used for high rise building, mostly Short pile can be typically 2-3m long and reinforced with steel, each pile is the connected with horizontal reinforced beam, where a suspended slab can be built on.
They transmit foundational loads through soil strata of low bearing capacity to deeper soil or rock strata of high load bearing capacity.