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Last edited 19 Dec 2022
 What are foundations?
Very broadly, foundations can be categorised as shallow foundations or deep foundations. Shallow foundations are typically used where the loads imposed by a structure are low relative to the bearing capacity of the surface soils. Deep foundations are necessary where the bearing capacity of the surface soils is not adequate to support the loads imposed by a structure and so they need to be transferred to deeper layers with higher bearing capacity.
 What are strip foundations?
Strip foundations (or strip footings) are a type of shallow foundation that are used to provide a continuous, level (or sometimes stepped) strip of support for linear structures such as walls or closely-spaced rows of columns that are built on top of the foundation, placed centrally along their length.
 When are strip foundations suitable?
Strip foundations are suitable for supporting linear loads in most types of subsoil, but they are most suitable where soil is of relatively good bearing capacity. They are particularly suited to light structural loadings such as those found in many low-rise or medium-rise domestic buildings - where mass concrete strip foundations can be used. In other situations, reinforced concrete may be required. Older buildings may variations on strip foundations such as brick strip foundations.
The size and position of strip foundations is typically related to the overall width of the wall they are supporting. The depth of a traditional strip foundation is generally equal to or greater than the overall wall width, and the foundation width is generally three times the width of the supported wall. This results in the load being spread at 45º from the wall base to the soil.
Approved document A of Building Regulations defines minimum widths for strip footings based on the type of ground and load-bearing wall, although it is generally advisable to consult a structural engineer when designing foundations.
 What sort of foundations might be used if strip foundations are not suitable?
Where ground conditions are poor, settlement is likely, or where it may be impractical to create individual strip or pad foundations for a large number of individual loads, raft foundations may be used. See Raft foundations for more information.
Where the bearing capacity of the surface soils is not adequate to support the loads imposed by the structure, deep foundations such as pile foundations may be used. See Pile foundations for more information.
Additional guidance is available in BRE's Simple foundations for low-rise housing: 'rule of thumb' design.
- Approved Document A.
- Bearing capacity.
- Brick strip foundation.
- Building foundations.
- Driven piles.
- Footings in foundations.
- How deep should foundations be.
- How to design a pad foundation.
- Pad foundation.
- Pile foundations.
- Raft foundation.
- Rubble trench foundation.
- Stepped foundation.
- Trench fill foundation.
- Types of excavation.
- Types of pad foundation.
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