Foundation problems: what to look out for

Types of foundation

• Timber piles: widely used in the west and north of the country until around the middle of the twentieth century. Wood is durable as long as it stays under water.
• Shallow foundation (fundering op staal): without piles, resting directly on a load-bearing layer. Susceptible to settlement if the subsoil sinks or dries out.
• Concrete piles: the standard technique in soft soils since the 1960s and 1970s.

What causes problems?

With timber piles, a falling groundwater level can lead to pile rot (paalrot): the pile heads are exposed to air and attacked by fungi. Bacteria can also slowly degrade wood. With shallow foundations, clay or peat drying out can lead to uneven subsidence, especially after dry summers.

Signs in and around the home

• Cracks in façades or interior walls, especially diagonal cracks above windows and doors.
• Sticking doors and windows, sloping floors or thresholds.
• A home that visibly differs from its neighbours in height or alignment.

Which public data helps?

The construction year, soil type, groundwater monitoring points and earlier public notices about foundation repairs in the street are objective starting points. Cone penetration tests and boreholes in the Basisregistratie Ondergrond (the national subsurface register) describe the soil structure in the area. The Klimaateffectatlas (Climate Impact Atlas) gives an indication of the risk of foundation damage at neighbourhood level.

How does a foundation survey work?

A foundation survey usually starts with archival research: building drawings and earlier reports from the municipal archive. A specialist can then dig an inspection pit down to the foundation, examine the pile heads, take wood samples and measure the groundwater level. Sometimes the floors and façades are also measured to establish any tilt. A survey typically costs a few thousand euros; with terraced houses it is often more efficient to investigate together with the neighbours, because the foundation of a block is interconnected.

If repair is needed

Foundation repair can easily cost tens of thousands of euros per home. Because homes in a block can share the same foundation, repairs are often carried out per block, in consultation with neighbours. Financing schemes exist, such as loans through the Fonds Duurzaam Funderingsherstel (Sustainable Foundation Repair Fund), and some municipalities have their own foundation advice desk. KCAF provides independent information on how to approach it.

Questions to ask when buying a house

• Has there ever been a foundation survey or repair on this home or the block? Ask for the reports.
• Has foundation repair been carried out in the street or neighbourhood before? Public notices and the municipality can show this.
• Are there any known cracks, sticking doors or sloping floors, and have they been repaired?
• Include a condition precedent (ontbindende voorwaarde) for a building survey in the purchase agreement, so you can still withdraw from the purchase if serious defects come to light.

Only an investigation of the home itself gives certainty: a foundation survey or a building survey. When buying, also ask about previous surveys and check the municipal archive.