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).