The most crucial part of any building is its foundations as they provide enough support to the structure in order to keep it upright. If you’re thinking of building or having serious work done on a property, it’s essential that you understand what’s going on underneath the surface.
Usually, foundations are split into two categories: Shallow Foundations and Deep Foundations, which refer to the depth of soil in which the foundation is made. Subsequently, there are a few different types of shallow and deep foundations. The type of foundations needed will depend on the following factors:
- Weight of building
- Wall construction type and height
- Soil type
- Drainage requirements
Here we’ll take you through the different building foundation types and advise on the types of buildings they are best suited to.
Shallow foundations are used for smaller buildings such as houses and can be made in depths of as little as 3ft (1m). Generally, when discussing shallow foundations it means that the depth in which the footing is placed is less than the width of the foundation. Types of shallow foundations include:
Individual footings are one of the most common types of foundations and are used when the load of the building is carried by columns. They distribute loads from the superstructure horizontally across sufficient surface area so that the bearing strength of the soil is not exceeded.
Holes are dug into the ground and fitted with a reinforcement cage then filed in with a concrete mix to ground level. Individual footings are often used to support lightweight structures such as timber-framed houses.
Strip footings are where concrete is placed into trenches and then built up to ground level using blockwork, where the walls then switch to brick or stone. They are often used where the building loads are carried by entire walls rather than isolated columns, such as in older buildings made of masonry.
Raft or Mat Foundations
Raft or Mat Foundations are used where the soil is weak, and therefore building loads have to be spread over a large area. They are often used in basements, where the entire basement floor slab acts as the foundation and the weight of the building is spread evenly over the entire footprint of the building.
Deep Foundations are used for large, heavy buildings like blocks of flats or offices and can be made at depths of 60 – 200 ft (20 – 65m). They are also used in environments where there is a layer of unsuitable soil at the surface that cannot support the weight of the building.
In this case, the load of the building must bypass this layer and be transferred to the layer of stronger soil or rock that’s deeper underground. Types of deep foundations include:
A pile is basically a long cylinder of a strong material such as concrete, timber or steel that is driven into the ground so that structures can be supported on top of it. You’ll need to find reputable piling contractors to install these types of foundations. They are used in the following situations:
- When there is a weak layer of soil at the surface which cannot support the weight of the building
- In a very heavy concrete building which will need very deep foundations to stabilise it such as a high rise block of flats.
There are two types of piles, they are:
End bearing piles
With end bearing piles, the piles are long enough so that the bottom end of the piles rest on a layer of very strong soil or rock, deep in the ground. The load of the building is then transferred through the pile onto this strong layer.
If the very strong soil or rock is too deep, friction piles can be driven into the ground instead. Here, the pile transfers the load of the building to the soil across the full height of the pile, by friction.
Dart & Co Foundations
Dart & Co Foundations are specialist UK Piling and Foundations Contractors that provide piling, underpinning and foundations solutions in the UK. For more information or to enquire about a project, please give us a call or fill out our contact form.