A prefab basement (Dutch: prefab kelder) is a cellar made in the factory as a ready-built, watertight concrete tank (or in large elements) and then placed on site in one go. Instead of casting the cellar in place and letting it cure, the heavy work is done in a controlled factory environment.
How it works
Once the excavation is dug and prepared to the right level, the prefab basement is lifted into the pit with a crane:
- Monolithic tank — smaller cellars arrive as one piece, watertight straight away.
- Element construction — larger cellars are built up from prefab wall and floor elements joined watertight on site.
- Fast placement — the cellar is often in position within a day.
Application
- Housing — extra space beneath a new-build home.
- Stores and plant rooms — quick, dry storage below ground.
Advantages and points to watch
- Speed — much faster than casting in place; short build time.
- Quality — factory production gives a consistent concrete quality and reliable watertightness.
- Groundwater — like any cellar, prone to uplift; the design must allow for it.
- Access — a crane and enough space are needed to lift the heavy tank; on existing sites this is not always possible.
- Ground investigation — have the groundwater level and bearing capacity determined beforehand.
Related terms
- Cellar
- Concrete
- Water barrier
- Excavation
- Foundation
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