Dränering

What dränering does

Dränering (drainage) is the system of pipes laid around the house foundation that carries water away before it reaches the foundation structure itself. It also keeps the groundwater level down around the house, so the footings (sulor) of the foundation are not in direct contact with free-standing water. It is the home’s most important protection against ground moisture.

If the drainage sits too high or has stopped working, the foundation can stand in groundwater, and that brings a real risk of moisture damage in the basement and foundation. The tricky part is that moisture from the ground moves slowly: it can take many years before the problem shows, so a dry basement today is no guarantee.

Lifespan and cost

There is no official lifespan for drainage, but the trade usually reckons a drainage system lasts around 25-50 years and is often ready for renewal after 25-35 years. Replacing it typically costs around 3,000-7,000 kr per linear metre, which for an average-sized villa (detached house) usually works out to roughly 100,000-250,000 kr. These are approximate trade ranges, not fixed prices, so use them only to get a sense of the order of magnitude.

What you should do

Ask the estate agent when the drainage was last replaced. If it is older than 25-30 years, it is reasonable to expect a replacement within the foreseeable future and to build it into your budget. And remember: drainage alone is usually not enough for a dry basement. The basement wall normally also needs moisture sealing on the outside. A surveyor (besiktningsman) can assess the condition on site if you are unsure.