Making Foundations On The Building Site
The foundations to a house are not a terribly glamourous affair. The site is normally begun with digging machinery of some type, mini digger or backhoe as a rule, and this when the site starts looking “like a building site”.
Once laid, the foundations are unlikely to be seen again for years, but they are one of the most important parts of the build, supporting the weight of the whole construction and have to follow the planning requirements to the letter.
At other points of the build, in the brickwork or carpentry, running alterations and changes can be addressed, but the foundations must be exactly in place first.
The type of foundation depends on the size of the structure, and most of all, on the make-up of the ground itself. If a professional ground survey is not carried out, then until the ground is broken into, the type of foundations intended can change, from what may have been an original assumption.
Soil types vary greatly in their strengths and stability, and soil with good structure is more stable. Clay textures are often better than sand textures because they have better structure, but a mix of particle sizes is best for foundation engineering.
Clay requires good run off to lessen the effects of expansion and shrinkage through moisture content and foundations are normally dug to a depth where the moisture content stays stable.
Dry, compressed gravel and sand will generally take a standard foundation, but trench walls may have to be reinforced until the concrete is poured in.
Firm chalk will take should take foundation works, provide the trench-work reaches a depth of around one metre to avoid any frost action. Run off is also important, given chalk’s liability of erosion.
Building on rock has obvious advantages, and if it has a high bearing capacity, such as solid hard chalk, granite, limestone sandstone etc. all that may be needed is to strip it back and build straight from it, once it is levelled. Precipitations, and waste water running can be problematic.
Poor subsoils may need an engineering approach. If they are water bearing, such as peat or water logged sandy type expansive soil, a reinforced concrete slab or raft which “floats” on or in the soil.
Few building sites start with ideal conditions, and good engineering designs will incorporate corrective measures and management practices, and it is important to know what soil properties exist to avoid future problems.