The frost line is the maximum depth to which the ground can freeze in winter. In the Netherlands, the frost line is approximately 60-80 cm below ground level. Foundations must be placed below this line to prevent frost damage: freezing water in the ground expands and can lift a shallow foundation.
Why is the frost line important?
Water in the ground expands by approximately 9% in volume when it freezes. If the ground beneath a foundation freezes, the foundation can be pushed upward (frost heave). This causes:
- Cracks in walls
- Subsidence after thawing
- Uneven settlement
Frost line in the Netherlands
| Region | Frost line (indication) |
|---|---|
| Coastal area | 50-60 cm (milder climate) |
| Inland | 60-80 cm |
| Eastern Netherlands | Up to 80 cm |
The official guideline: place foundations at least 80 cm below ground level. With a frost skirt, shallower foundations are possible.
Frost line in DIY projects
| Structure | Minimum foundation depth |
|---|---|
| Strip foundation (garage, shed) | 60-80 cm |
| Pad foundation (garden building) | 60-80 cm, or use a frost skirt |
| Concrete slab | Use a frost skirt with a shallow slab |
| Fence posts | 60-80 cm deep |
Related terms
- Frost skirt
- Shallow foundation
- Pier (pad foundation)
- Concrete slab (floor slab)
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