Foundation and drainage: lifespan and cost
The foundation holds the house up and the drainage keeps water away, and it is moisture at the bottom that causes the most expensive damage. The table shows how long the parts last and what a fix usually costs.
The ranges apply to a normal house. Actual cost depends on size, access and region. Lifespan means technical lifespan with normal upkeep.
| Component | Lifespan | Replacement cost |
|---|---|---|
| Foundation wall | 80 yrs (60-100) | 150 000-500 000 kr |
| Drainage | 32 yrs (25-45) | 150 000-350 000 kr |
| Crawl space | 50 yrs (40-70) | 80 000-250 000 kr |
| Slab-on-ground | 80 yrs (60-100) | 100 000-300 000 kr |
How long does drainage last?
The foundation wall itself is nearly permanent, but the drainage around the house is a wearing part that needs redoing at intervals. When it stops leading water away, moisture rises in the foundation wall and basement. Signs are damp or salt on the basement wall and water pooling near the house. See the dedicated page on drainage for when it needs redoing.
What does redoing the drainage cost?
Redoing the drainage means the ground is dug up around the house, new drainage and moisture proofing are laid against the foundation wall and the soil is filled back. The price is driven by how deep it is, how close the house sits to the plot boundary and shrubbery, and whether the ground slopes. Crawl spaces and slab-on-ground have their own risks and fixes. The cost in the table applies to a normal house.
What the age of the house tells you
Some build years carry known risks for exactly these parts. Here are the most common ones.
Dry rot (Serpula lacrymans) Houses built 1800–1960
Dry rot — rare, but the most destructive wood-rotting fungus.
Radon (bedrock) Houses built 1800–2026
Norway has high radon levels because of granitic bedrock, especially in basements.
Crawl space — moisture problems Houses built 1950–1980
Crawl spaces from this period often have insufficient ventilation.
How do I know if the drainage needs redoing?
Ask for the year of the last drainage work. Damp, a musty smell or salt deposits on the basement wall and water pooling against the house are signs it is no longer doing its job.
Is a crawl space a risk?
Crawl spaces from certain years often have poor ventilation and ground moisture barrier and can develop mould. Checking smell and moisture in the crawl space is part of a condition report; see the age note below.
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