Foundations are the least glamorous but most important part of any building project. Get them right and everything above works. Get them wrong and you have expensive problems you cannot easily fix later. Here is how we choose the right foundation for projects across Warwickshire.
The five common foundation types
Strip foundations
A continuous strip of concrete running below load-bearing walls. The default choice for most extensions in stable ground. Typical depth 1–1.5m.
Trench fill foundations
A wider, deeper strip filled with concrete right up to near-ground level. Faster to build than strip foundations because there’s no need to build up in bricks or blocks from the base. Common on newer housing developments.
Raft foundations
A single reinforced concrete slab covering the whole footprint of the building. Useful where the ground bearing capacity is low, or where individual strip foundations would need to be very deep. More expensive but predictable.
Pile foundations
Concrete columns driven or bored deep into the ground to reach a stable stratum. Used on very poor ground, near trees, or where existing services or basements prevent traditional foundations. Piles are then connected by a reinforced ground beam.
Pad foundations
Individual square or rectangular concrete pads under specific load points (e.g. steel columns). Common on portal-frame commercial buildings and some timber-frame houses.
How we choose
The choice depends on:
- Ground conditions: Warwickshire has a mix of clay, gravel and made ground. A ground investigation report tells us what we’re dealing with.
- Trees nearby: Trees affect clay soil to depths of 3–4m or more. NHBC guidelines give minimum foundation depths depending on tree species and distance.
- Slope: On sloping sites we sometimes need stepped foundations or retaining structures.
- Existing services: Drains, gas, water and cables all constrain where foundations can go.
- Building load: A single-storey extension is much less demanding than a full two-storey house.
When to pay for a ground investigation
For extensions on established houses in known-good ground, a full ground investigation is often not needed. For new builds, extensions on sloping sites, or extensions near mature trees, a Site Investigation Report (SIR) from a geotechnical engineer is money well spent. It stops you from over-specifying (wasting money) or under-specifying (creating future problems).
Serving homeowners across Warwickshire, Worcestershire, Gloucestershire and the wider region.