A foundation is the lowest and supporting layer of a structure. Foundations are generally divided into two categories: shallow foundations and deep foundations.

Pile foundation/deep foundation

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 foundation type, a waterlogged area of high building may also require this.

It is the costliest hence it is used for high rise building mostly.There are different types of deep footings including impact driven piles, drilled shafts, caissons, helical piles, geo-piers and earth stabilized columns. The naming conventions for different types of footings vary between different engineers. Historically, piles were wood, later steel, reinforced concrete, and pre-tensioned concrete.

Cost of pile foundation

Cost of pile foundation depends upon the  type of soil,Design of the pile foundation and the design of the building.

Shallow foundations

1)Spread footing /Strip foundation: This is the most common type, it is mainly used where you have strong soil base and non-waterlogged areas. Most small buildings of just a floor are constructed with this type of foundation. It consists of strips or pads of concrete (or other materials) which extend below the frost line and transfer the weight from walls and columns to the soil or bedrock.

2) Pad foundation-This is where isolated columns (pillars) are cast from the foundation to carry a slab at the top of the ground. This is mostly used when you want to make use of the under of the building as parking space or when the other space is not conducive to have the foundation. Imagine you are planning to build a house across a flowing stream and you want a situation where you can use your boat to pass under the building because the stream is under. Then you may not need to dig foundation that will cut across the river but just by applying columns (pillars) at the edge of the river like a bridge, this columns are thus isolated and there foundations are referred to as pad.

3)Raft foundation-This is where you have concrete spread around your building from the base of foundation all through to the german floor/oversite concrete/ground floor slab. It is mainly used in areas where the soil are sandy and loose, 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
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 are usually from 600mm to 1200mm for low buildings.