Groundwork is the excavation and soil preparation needed before you can build — think of digging for foundations, pipes, drainage and site levelling. Nearly every construction project starts with groundwork. For DIYers, groundwork comes into play when building a garden shed, outbuilding, driveway, pond or drainage runs.
Types of groundwork
| Type | What | Example |
|---|---|---|
| Excavation | Removing and disposing of soil | Foundation pit, cellar |
| Trench digging | Digging narrow channels | Foundation trenches, pipe runs |
| Raising | Adding soil or sand | Raising ground level for driveways or gardens |
| Levelling | Making terrain flat | Preparation for paving |
| Compaction | Tamping or vibrating soil | Creating a load-bearing subgrade |
| Disposal | Removing surplus soil | Skip or truck |
Groundwork for a foundation
When pouring a foundation (e.g. for a garden shed or outbuilding):
1. Set out — Mark the outline with pegs and string
2. Remove topsoil — Strip the top 20-30 cm (humus) and keep it aside
3. Dig foundation trench — At least 80 cm deep (below the frost line)
4. Compact the base — Tamp down with a plate compactor or rammer
5. Lay sand bed — 10-15 cm sharp sand, compact
6. Reinforcement and concrete — Set formwork and pour concrete
Soil types
| Soil type | Load-bearing capacity | Considerations |
|---|---|---|
| Sand | Good | Easy to work, water-permeable |
| Clay | Moderate-good | Swells/shrinks with moisture, hard to dig when wet |
| Peat | Poor | Soft, compressible, often needs piled foundations |
| Loam | Moderate | Water-retaining, difficult in rain |
Cost guide
| Job | DIY | Hire out |
|---|---|---|
| Foundation trench (10 m) | Free (+ sweat) | €200-400 (mini excavator) |
| Mini excavator hire | €150-250/day | — |
| Soil disposal | €15-25/m³ (skip) | €25-40/m³ |
| Fill sand delivery | €15-25/m³ | Including delivery |
Common mistakes
- Not digging deep enough — Foundation above frost line = risk of frost heave
- Not locating services — Contact your utility locator service before you dig
- Not compacting soil — Settlement and subsidence over time
- Not keeping topsoil separate — You’ll need it later for the garden
Related terms
- Foundation
- Strip foundation
- Concrete slab
- Frost line
- Reinforcement
- Drainage