First, investigate what type of foundation the home is likely to have and what is known about the property and the surrounding area. The year of construction, a risk map or a visible crack is only an indication. Reviewing the documents and, where necessary, arranging a specialist foundation survey are the only ways to get enough clarity for your purchase decision.
Do not wait until after the purchase. Uncertainty about foundation risk can affect the value, your offer, your financing and the costs you may later have to pay as the owner.
Step 1: identify the foundation type
Start by finding out what the home rests on. Wooden piles and shallow foundations are relatively common in older homes. The year of construction alone is not proof: the soil, groundwater, construction method, alterations and load on the property also play a role.
Look for architectural drawings, structural drawings, pile-driving records and information in the municipal building archive. Also ask the seller whether the foundation type has previously been established. If the answer is only an assumption, record it as an assumption.
An unknown foundation type does not automatically mean that the home has a poor foundation. It does mean that you do not know enough yet.
Step 2: review information about the surrounding area
Check whether the municipality has a foundation information desk, foundation map, land subsidence data or other local information. The national Funderingsviewer can also show indicative areas of concern. These maps can help you decide whether to investigate further, but they do not provide a technical assessment of the home itself.
A favourable colour on a map is therefore not a guarantee. Nor is a lack of data. The information may be based on models, characteristics of an area or data from nearby properties. You should also look at the block and the street:
- Have foundation problems been identified in neighbouring properties?
- Have any homes visibly been repaired or had new foundations installed?
- Are subsidence measurements or groundwater measurements available?
- Are there works or developments that could be relevant?
Step 3: request the complete documents
Do not simply ask whether a survey has “ever been carried out”. Request the original report. Check its date, which properties were investigated, which measurements were taken and what limitations the surveyor mentions.
In any case, ask the seller about:
- previous foundation surveys, QuickScans and subsidence measurements;
- known cracks, subsidence and sticking windows or doors;
- repair work and the reason it was carried out;
- permits, invoices, guarantees and drawings for completed repairs;
- reports or investigations concerning adjoining homes;
- agreements about monitoring or groundwater measures.
An old report may still contain useful information, but its conclusion may no longer be current. For example, check whether monitoring was recommended and whether those measurements were actually carried out afterwards.
When buying an apartment
In addition to technical reports, request the documents needed to check the VvE: the deed of division, the division regulations, the meeting minutes, the maintenance plan and information about the financial reserve. Look for previous reports, quotations and decisions about investigations or repairs.
Then check whether the foundation is part of the common areas, how costs are divided under the division documents and which decisions still need to be made. With a VvE, you depend on the available funds and the VvE’s decisions; the required majority is set out in the division documents.
Even with a house, the structure may be part of a larger block. Investigating or repairing only your future home may not always be technically or practically possible.
Step 4: look for warning signs during the viewing
Cracks in façades and walls, sloping floors, sticking doors and windows, or a difference in height compared with neighbouring properties may be reasons for further investigation. Also inspect the connections between properties, the front and rear façades, and the overall street view.
Look out for conspicuously new plasterwork, recent repointing or localised repairs. Ask why this work was carried out. A repair may be routine maintenance, but it may also conceal damage.
These signs are not a diagnosis. Cracks and leaning can have other causes. Conversely, there may be a foundation problem without any obvious damage being visible during a viewing. KCAF lists cracks, sticking windows and doors, and leaning as possible warning signs, but also stresses, for example, that cracks can have other causes.
Step 5: decide what investigation is needed
A standard building survey may identify above-ground warning signs. Such a survey usually does not provide a complete assessment of the foundation’s technical condition and remaining lifespan. Ask explicitly in advance what will and will not be investigated.
If the uncertainty is limited, reviewing the documents or arranging a QuickScan may help clarify the risk. If serious questions remain, a specialist foundation survey may be necessary. An investigation following the KCAF guidelines may include archive research, measurements of leaning and subsidence, an assessment of cracks and an inspection of the foundation.
Ask a foundation specialist to advise you on the appropriate level of investigation. Agree in advance:
- which question the investigation must answer;
- which parts of the property or block will be included;
- whether inspection pits and access to other homes are needed;
- how current and useful the conclusion will be for the valuation and financing.
Further investigation is an obvious step when several factors come together, such as an unknown or vulnerable foundation type, an elevated risk in the area, problems affecting neighbours, visible warning signs, or missing and conflicting documents.
Arrange the investigation before making an unconditional offer
Try to get the clarity you need before making your offer. This prevents you from being contractually committed while access to the home, crawl space or neighbouring properties still needs to be arranged.
If an investigation cannot be completed beforehand, include a specific condition in your offer. Record, among other things, what investigation may be carried out, who chooses the specialist, who pays the costs, what deadline applies and what outcome allows you to withdraw or renegotiate. A general condition for a building survey does not necessarily cover a specialist foundation survey.
Translate the outcome into your offer and financing
Do not only consider whether immediate repairs are needed. A report may also recommend monitoring, a new investigation within a few years or preventive measures. You should therefore prepare several cost scenarios.
In addition to foundation repairs, take into account the cost of investigations, structural advice, permits, repairing floors and walls, pipework, finishing work and possibly temporary accommodation. For a block or VvE, the schedule and costs may also depend on other owners.
Do not automatically treat this uncertainty as a single amount to deduct from the asking price. Also assess whether you can finance the work, when it needs to be done and whether the home will still suit your budget and plans afterwards.
Since 1 April 2026, the model Taxatierapport Woonruimte has included more specific information about foundation risk, using classes A to E. For class D or E, an additional limited foundation investigation is generally required. The valuer takes the outcome into account when assessing the value. The mortgage lender then decides how the risk and any future costs are factored in.
Discuss any known or suspected foundation risk with your mortgage adviser before making a binding offer. The valuer will later make an independent assessment. Ask which reports your intended mortgage lender requires and what a lower valuation or a requirement for further investigation could mean for your maximum mortgage.
Do not assume in advance that a special repair scheme will be available. The Funderingslening Maatwerk is intended as a safety net for certain existing owners who cannot finance necessary repair costs through a standard loan. The scheme is not a guaranteed solution for your purchase.
When do you know enough?
You do not need to open up the foundation of every older home immediately. But you should be able to explain what your decision is based on. Are the foundation type, local information and existing reports consistent and current, with no additional warning signs? If so, reviewing the documents may provide enough certainty.
Are essential details missing, do sources contradict each other or are several warning signs present? Do not treat “unknown” as “good”. Arrange an appropriate investigation or address the uncertainty specifically in your conditions, financing and offer.
