Anyone considering or currently undertaking a self-build project will be aware of how much planning and work is involved, but did you know that the type of soil you build on can have a dramatic effect on which foundations are suitable?
Foundations are essential to evenly spread and carry the weight of a building over the ground surface, and the foundation you choose will depend on the soil type being built on.
In most cases your local authority will be able to tell you the soil type of the plot you’re building on, but it’s important to be aware of the different types before you plan your build. With this in mind, see our handy guide below for the different types of soil and the most suitable foundations.
Common types of rocks include limestone, granite, sandstone or shale, and all have a high bearing capacity as they are more dense and solid than softer ground types. In some cases, the rock can simply be stripped and levelled off to provide a suitable building surface, or you can use a strip, pad or raft foundation.
The top layer of clay (up to a depth of 1,200mm) is prone to expansion on shrinkage depending on the moisture content, so it’s vital to excavate foundations to a point where the moisture content is stable. With firm clay, the trench is often lined with a compressible layer such as clayboard before the foundations are concreted.
As you might expect, soft clay is much more unstable so requires a more secure foundation. A common solution is to use a wide strip foundation with steel reinforcement, although an engineered foundation may be needed in some cases.
Peat is a pretty unreliable soil to build on, but it is possible. If the peat can be stripped back to find suitable ground to bear weight (at a depth of at least 1.5 metres), then it may be possible to use strip foundations. If not, then a reinforced raft foundation should provide the strength required.
Chalk soils are susceptible to erosion, so bear this in mind when building on this type of ground. Strip foundations are the most suitable for chalk; these are concrete strips which support load-bearing walls, and can be reinforced with steel to increase their load-bearing capacity. Just bear in mind that if the chalk is soft it will have to be excavated until you reach firmer ground.
If you need expert piling or foundations for your next building project, get in touch with 118 Foundations. We specialise in mini piling, grundomat piling, excavations, new build foundations and much more, and are on hand to give you specialised advice about which foundation will work best for your project. For more information or to discuss your requirements, give us a call or visit our website today.