Groundworks & Foundations in Berkshire

What affects the cost of groundworks?

Ground conditions are the biggest variable. Clay soils require deeper foundations. High water tables, made ground, or contaminated land all add cost. Tree root protection zones, proximity to drains, and access for machinery all affect price. We identify the key risks at the initial site visit.

Do I need a soil investigation before starting groundworks?

For most residential extensions, an experienced builder can assess ground conditions visually and through local knowledge. For new builds, larger extensions, or sites with unusual ground conditions, we arrange a soil investigation report. We advise at the initial visit.

Do you take on groundworks-only contracts?

We do not take on groundworks-only contracts. Groundworks is delivered as part of a full extension, renovation, or new build project.

How long do groundworks take?

Typically 2–3 weeks for a standard single storey extension, depending on footprint and ground conditions.

How deep do strip foundations need to be for a single storey extension?

The minimum depth for strip foundations under most domestic extensions is 600mm below finished ground level. On shrinkable clay soils — common across Bracknell, parts of Reading, and the London Clay belt — building control typically requires 900mm–1000mm depth to get below the zone of seasonal movement. We always have the ground investigated at the initial visit and include the correct specification in the quote.

What is the difference between strip foundations and raft foundations?

Strip foundations follow the line of the walls — they are concrete trenches under each loadbearing wall. Raft foundations are a continuous reinforced concrete slab under the full footprint of the building. Raft foundations are used where the ground is variable, where there is a risk of differential settlement, or where the soil bearing capacity is low. We specify the correct type based on ground conditions at your site.

When does groundworks require building control inspection?

Building control must inspect foundations before concrete is poured — this is a mandatory inspection stage. They check the trench depth, width, and bearing capacity of the soil. We book this inspection as part of our programme and ensure the ground is ready before pouring. Do not pour concrete without the inspection — it will need to be broken out.

What drainage work is typically included in extension groundworks?

Extension groundworks typically include: excavation and laying new below-ground drainage from the extension to the existing drain run; installation of a new rodding eye or inspection chamber; diversion of any existing drainage affected by the new footprint; and surface water drainage from the new roof. All drainage is installed to Building Regulation Part H requirements and inspected before backfilling.

What is a ground beam and when is it used?

A ground beam is a reinforced concrete beam spanning between pile heads — used where the bearing stratum is too deep for conventional strip foundations. Ground beams are common on sites with deep soft clay, filled ground, or where trees have caused extensive shrinkage. We commission specialist ground investigations if there is any doubt about bearing conditions at your site.