Groundworks Costs in Wales 2026
Groundworks costs in Wales vary significantly by job type, depth of excavation, ground conditions, and access. Welsh geology — including made ground in South Wales valleys, clay in coastal areas, and rock in upland regions — affects both cost and programme.
Typical groundworks costs in Wales:
| Job type | Typical cost range |
|---|---|
| Strip foundations (per m run) | £80–£180 |
| Concrete slab (per sq m) | £100–£200 |
| Raft foundation (per sq m) | £150–£280 |
| Deep pile foundation (per pile) | £800–£2,500 |
| Drainage installation (per m run) | £40–£120 |
| Soakaway installation | £600–£1,800 |
| Retaining wall (block/concrete, per m) | £200–£450 |
| Excavation and removal (per cubic m) | £50–£120 |
Groundworks typically represent 15–25% of a building project's total cost. In Wales, factors that add cost include: sloping sites (common in valley and hillside locations), high water table (coastal South Wales), and rocky ground (Mid Wales and North Wales).
Types of Groundworks in Wales
Strip foundations: The standard for most extensions and new builds in Wales. A trench is excavated, concrete poured, and the blockwork base built up from below ground level.
Concrete slab: Used for outbuildings, garages, and some extensions. Cost depends on thickness (100mm domestic vs 150–200mm for commercial loads) and reinforcement requirements.
Drainage: New drainage systems — soakaways for surface water, foul drainage connections — often form part of groundworks packages. In Wales, groundwater conditions and Environment Agency guidance on soakaways (not permitted in some Welsh areas) affect options.
Retaining walls: Common in Wales given the sloping terrain. Costs depend on height, backfill conditions, and whether engineering design is required (walls over 600mm typically need structural calculation).