When building on rock, there are two things to consider. Firstly, most rock is very good at bearing heavy loads, so sometimes the actual foundation installation requires minimal work. But as rock doesn’t deal well with water, topsoil usually needs to be implemented to assist with drainage.
We’ll usually opt for strip foundations with chalk sites. A width of around 450mm is usually sufficient for smaller buildings, with a depth of around 700mm. It depends on how hard the chalk is, however. If we find soft chalk we’ll need to dig down until we find the hard variety.
Again, strip foundations are usually the optimal choice here, to a depth of 700mm depending on load bearing capabilities. In the case of sand, sometimes we can employ sheet piling to hold the ground in trenches while we add in concrete.
The main concern here is the expansion/contraction of clay based on moisture content. This means our groundwork contractors will usually dig below 1m, to reach more stable clay and allow for some movement. If it’s an especially volatile area, we might dig further down to a maximum of 3m.
If we’re lucky, we’ll dig down at least 1.5m and find more suitable load-bearing ground beneath the peat. But oftentimes, we’ll need to use a reinforced raft foundation installation to get the job done.
While not quite a soil type, it’s worth noting that if your building site is on an incline, then we will need to use a stepped foundation to provide proper support.
Designed to support load-bearing walls, these are usually 450-600m wide (single-storey vs two-storey), and 200mm deep. Made from concrete, they take the form of a continuous strip. There are also deep strip foundations, designed for jobs where we need to dig down to reach suitable ground. Wide strip foundations, on the other hand, are ideal for soft soil as they spread the load over a greater area.
A very common foundation type for projects in Surrey, these are one of the lowest cost varieties. Simply put, we dig to a depth where we can find sufficient load-bearing characteristics, then fill the entire trench with concrete. Sometimes steel is added in if there are nearby trees, whose roots could otherwise compromise the foundation installation over time.
This approach involves the use of columns which are 2-3m long, driven into place. Each column is joined by a reinforced concrete beam. Then a suspended ground floor is built on top. Columns are pre-fabricated or built on site, depending on the job at hand.
Ideal for weak/expansive soils like peat and softer clays, these get their name from allowing a property to “float” on the soil. They’re made from reinforced concrete poured into a large slab which helps spread the load.
Every type of foundation fulfils the same purpose – to evenly spread the weight of a structure over enough of a surface that the subsoil below doesn’t move and make the structure uneven, or at risk of collapse.
When you next require foundation installation in Cobham, Claygate, Haslemere, Guildford, Farnham, Woking, Weybridge or the surrounding areas, get in touch with the expert team at Lucas Groundworks. We’ll conduct a site survey and draw up precise plans to ensure your foundations support further building work, and last indefinitely.
You can reach us on 01483 861 187. Our groundwork contractors can handle foundation installation for anything from an extension in Guildford, to a new office scheme in Farnham.
