Laying a Foundation: How to Choose the Right One

There are many different types of foundation that can be used to build your property or extension on, and it is important to know which will be the best solution for you. Variables such as soft ground, closeness of trees and drains, as well as wind speed, all affect what type of foundation you should use to build on.

For our latest post, we have put together a list of the different types of foundation available to you and the key features of each option.

Strip Foundation

This type of foundation is the most common and is used to build the majority of properties within the UK. Trenches are dug at least 150mm deep and are filled with concrete, creating a strip of concrete around the area of the property. In general, it is a rule that the distance from the front face of the wall to the edge of the foundation will be equal to or less than the depth of the foundation, as long as the foundation exceeds 150mm.

It is important to consider the proximity of trees when thinking of laying a strip foundation as the moisture they use will cause the ground to rise and fall. When a tree is chopped down, it can cause the ground to swell up due to the lack of moisture and could cause potential issues surrounding drainage of the property. For detailed information on strip foundations, have a look at this article from ‘Construction Studies’.

Trench Fill Foundation

Trench fill foundations are thinner in size than strip foundations but thicker in concrete. This type of foundation is preferred by self-builders, and so may be a good option if you are planning to build your own property. Best used in clay and chalk soils, trench fill foundation must be used on stable ground as the sides of the trench play a big part in supporting the home; due to the amount of concrete being poured to fill the entire trench, this solution rules out the need to use bricks below the surface.

Engineered Foundation

This option covers numerous types of foundation, all of which are called engineered foundations as they often require a structural engineer to advise the best solution. The most common engineered foundation involves building deeper trenches and filling them with more concrete, usually placing polystyrene sheets to prevent slipping.

If the trenches need to deeper than 2.5m, you will need to build different foundations as the amount of concrete used becomes incredibly expensive and the depth creates more danger for work. The decision to choose engineered foundations is difficult as they are more expensive and time consuming to build, but are the perfect option for building on difficult ground. Two of the engineered foundations available to you are:

1.    Piling

Piles are built into the ground vertically and filled with concrete. The entire foundation then lies of the piles and the ground beam that will hold the house. This option is particularly useful when building on water or really wet soil.

2.    Rafts

A concrete raft designed to float on the ground you are planning to build on will act as the foundation for your home. If your land is prone to flooding, or weather conditions are a worry, this option can help prevent damage to your property. For more information on raft foundations, have a look here.