Groundworkers: What They Do and When You Need One
Foundations, drainage and site prep — the first trade on any extension.
4 min read · Updated 2026
Key takeaways
- ›Groundworkers do the foundations, drainage and slab — before the bricklayer starts.
- ›Strip foundations cost £100–£150 per linear metre.
- ›Always agree who obtains Building Control sign-off for the foundation depth.
What a groundworker does
Groundworkers prepare the site: stripping topsoil, excavating trenches for foundations, pouring concrete, laying drainage and soakaways, building the sub-base, and casting the floor slab. They also install drainage runs to the sewer and handle muck-away. On most extensions they are the first trade on site and work to Building Control for foundation depth.
Typical prices (UK 2026)
- •Strip foundation (dig + concrete): £100–£150 per linear metre.
- •Soakaway crate system: £400–£900.
- •Drainage run (new): £80–£150 per metre.
- •Concrete slab (supply + lay): £60–£100 per m².
- •Muck-away grab lorry: £250–£400 per load.
Questions to ask and common mistakes
Ask whether they arrange Building Control inspections and whether muck-away and concrete are included. Common mistakes: digging foundations too shallow for the soil, not allowing for the concrete pour in the price, and poor compaction of the sub-base causing the slab to crack.
- ☐Do you arrange Building Control inspections?
- ☐Are concrete, muck-away and plant hire included?
- ☐What depth will the foundations be dug to?
- ☐Who signs off the drainage connection to the sewer?
Frequently asked
Do I need a groundworker or a builder?
Many builders include groundworks in a package; on smaller jobs a dedicated groundworker may be cheaper. For a new build or large extension, a specialist groundworker is usually better.
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