Knowledge base foundation investigation

Anyone buying a house in Amsterdam that was built before 1970 is almost always buying a house on timber piles. You cannot see how those piles are doing, and the seller often does not know either. Even so, the foundation is the item that can change a purchase more than any other. This knowledge base covers foundation investigation from the buyer’s point of view: what you can check beforehand, what a quick scan during the building inspection does and does not show, how to read measurement values, and what to do when the result is disappointing.

Nederlandse versie: kennisbank funderingsonderzoek

We are Premiumkeur, a cooperative of building inspectors with its head office on the Heiligeweg in Amsterdam. All Premiumkeur inspectors carry out foundation investigations. If you want to go deeper into foundation repair, monitoring bolts and the different investigation phases, you will find that on our site on foundation investigation.

In brief

• Until about 1970, homes in Amsterdam were usually built on timber piles. The year of construction says something about the type of foundation, but nothing about its condition. Our advice: have the foundation investigated before you buy any house built before 1970.
• We carry out a foundation quick scan (phase 0) during the building inspection. Together they cost from € 898; the quick scan itself then costs € 399.
• A quick scan measures tilt, but it does not see the piles. Only an investigation in which the foundation is dug open (phase 2) shows the piles themselves.
• Foundation repair costs from € 2,500 per m², from € 3,500 per m² with a cellar, and the finishing work comes on top. That makes it the most important question for an old house.
• We work only for buyers and owners, not for sellers, and we do not recommend foundation repair companies or contractors.

1. Why the foundation is the biggest uncertainty when buying in Amsterdam

Amsterdam stands on soft ground. Until about 1970, homes here were often built on timber piles (RVO (in Dutch)). As long as those piles stay below the groundwater, they can last a long time. In our practice we see timber piles stay in good condition for about ninety years on average, but that is an average, not a guarantee for any particular building.

The causes we meet most often in Amsterdam are bacterial attack of the pile wood, rot at the pile head, and piles that were set too shallow at the time. Drying out because of a groundwater level that is too low almost never happens in Amsterdam, because the groundwater here is high.

The difficulty for a buyer: from the outside you only notice something once the foundation has already subsided considerably. Cracks, sloping floors and sticking doors can also have other causes. Only measuring tells you how the building stands, and only digging tells you what the piles look like.

2. Foundation label (funderingslabel), foundation map and what they do not tell you

The foundation label in the valuation report

Since 1 April 2026, every valuation report contains a foundation label from A to E (Ministry of the Interior and Kingdom Relations (BZK) (in Dutch)). The valuer sets the label based on visible signs and online data. It is a risk indication, not a foundation investigation. So it says nothing definitive about the technical condition or the remaining life of the piles. An A does not mean you do not need an investigation, and a D or E does not automatically mean the foundation is bad.

Foundation map and foundation code

For many Amsterdam buildings there is a foundation code or an entry on a foundation map. That information is often old and not always reliable. In one of our cases, the municipal map reported repair in an earlier year, while the building archive held no documents about it. Use such a code as a reason to ask further questions, not as an answer.

The building archive

The Amsterdam building archive is public and free to consult. There you can find drawings and earlier permits, for example for a foundation repair or for a renovation in which a floor was replaced. With a phase 1 investigation we can do the archive research for you.

3. Step-by-step plan: foundation investigation when buying a house

1. At the viewing. Look for tilting facades and floors, joints that run at an angle, cracks above windows and doors, sticking doors, and a clear difference with the neighbours. Ask about the year of construction, foundation repair, monitoring bolts and, for an apartment, what the owners’ association (VvE) knows about the foundation.
2. Offer subject to a purchase condition (voorbehoud). Include a condition allowing you to withdraw if a building inspection turns up problems. Call us straight after the verbal agreement; the condition period usually lasts only a few weeks.
3. Inspection with foundation quick scan. During the inspection we measure the bed joints and level the floors. Inspection and quick scan together take about an hour and a half. You will have the report within two working days.
4. Reading the result. If the building is within the usual margins, there is no reason for further investigation above ground. That does not give certainty about the piles; that can only be had by digging.
5. If in doubt: follow-up. A more extensive investigation above ground (phase 1), an investigation in which the foundation is dug open (phase 2), or monitoring bolts to follow the subsidence over the years.
6. Decide. With the result you can negotiate on the price, make additional agreements, or dissolve the purchase within the purchase condition. We do not give legal advice; discuss this with your buyer’s agent or lawyer.

Watch the time. A phase 2 investigation takes about one and a half to two months from order to report. That often does not fit within a purchase condition of a few weeks. If you want that certainty up front, discuss at the time of bidding whether there is room for it, or have such an investigation done before you make an offer.

4. What a foundation quick scan measures

We assess the measurements according to the guideline of the KCAF, the Knowledge Centre for Foundation Problems (Kenniscentrum Aanpak Funderingsproblematiek). A tilt is a snapshot: it shows how much the building has subsided in total, not how fast it is subsiding now. For that you need repeated measurements with monitoring bolts.

5. Reading measurement values

• Tilt is expressed as a height difference over a length, for example 30 mm over 6 metres. In our reports we compare it with the limit values from the KCAF guideline.
• Rate of subsidence comes from monitoring bolts measured over several years. In our practice, Amsterdam buildings subside by about 1.5 mm per year on average; above 2.5 to 3 mm per year we find it worrying.
• Monitoring bolts in Amsterdam are often only on the front facade. The measurement then says something only about that side of the building. We place at least eight monitoring bolts, on all load-bearing walls; 8 to 10 bolts cost € 1,179, a repeat measurement € 816.75.
• After a renovation, facade and floor only show the tilt since that renovation. A low result then does not mean the foundation has been renewed.

6. Apartments, the owners’ association and the neighbours

Most homes in the old city are apartments in an owners’ association. Foundation repair to the building is paid for by the owners’ association, and each owner contributes in proportion. So before buying, ask for the minutes, the multi-year maintenance plan, the state of the reserve fund, and any earlier foundation investigations or monitoring bolt data. If foundation repair is already on the agenda, you want to know what your share will be and whether the owners’ association has the money for it.

If the building shares a party wall with the neighbours, their consent is usually needed for repair and they often pay a share. If you want to divide a building into apartments, a phase 2 foundation investigation is generally required, and if the result is poor, the foundation has to be renewed.

7. What repair costs and how long it takes

For foundation repair we deliberately quote a price per square metre and not a total amount, because the differences between buildings are large. Amounts include VAT, Amsterdam, 2025 price level, starting prices:

In practice, repair and renovation together take at least eight to twelve months. Keep in mind that during that time you will have to live somewhere else, with removal and storage costs, and that you may have double housing costs for a while.

8. Cost of the investigation

9. A free inspection: what to look out for

You will come across offers for a free foundation check, a free roof inspection or free leak detection. These are often companies that also carry out the repair afterwards: foundation repair firms, roofers and plumbing companies. Free usually means you do not pay separately for the inspection; the cost is earned back through the work that follows. The party who assesses the problem then also earns from the solution. Many tradespeople work honestly, but the advice is harder for you to check.

Foundation repair involves large sums. So always ask which measurements were taken, have an independent report made before you request quotes, and have several parties quote on the basis of the same report. Be extra careful with doorstep selling, pressure to decide quickly and cash payment. For an agreement made at the door above € 50, you have in principle a 14-day cooling-off period according to the Rijksoverheid (in Dutch).

10. Practical cases: thirteen foundation investigations in Amsterdam

These cases come from our own reports of 2025 and 2026: foundation investigations and quick scans during inspections. They show how different the result can be for buildings from the same period, and why measurements say more than a year of construction or a label. Addresses and names have been left out; the borough comes from the postcode. Amounts are given only where the report mentions them.

Case 1: Sunken bathroom floor and tilted staircase, Amsterdam-West

Situation. Apartment in a building from 1890 with five storeys, owners’ association yes. February 2026. The resident reported that the floor joists seem to slope down towards the bathroom. Foundation risk quick scan.

Findings. Bed joint measurement: front facade straight between the measured points; rear facade not accessible. Floor levelling (± 2 mm): moderate to very large subsidence towards the bathroom, slight tilt towards the rear (negligible to small) and to the left. Staircase: rotations 1:23 to 1:44, KCAF very large. Ground floor staircase: rear left -13 mm, rear right -9 mm, front left -3 mm, front right 0 mm. The archive and foundation map are not mentioned.

Advice and costs. Bathroom: inspect the floor joists with an endoscope through the ceiling of the downstairs neighbours, and if needed call in a structural engineer afterwards. Foundation: no immediate high risk; place monitoring bolts, or go straight to phase 2. Staircase: make a crawl space hatch and inspect the crawl space. No amounts in the report.

What this shows. Floor subsidence and the foundation can have different causes and each calls for its own next step.

Case 2: Tilted cellar under a level raised ground floor (bel-etage), Amsterdam-Centrum

Situation. Ground-floor apartment from 1828 with two storeys, owners’ association yes. March 2026. An independent building inspection with foundation quick scan investigation was requested.

Findings. Floor levelling of the raised ground floor: the floor is level. Cellar: 7 cm (70 mm) height difference between front and rear facade; length, rotation and KCAF category are not in the report. Damp patches and mould were seen near the wastewater pumps, black damp patches in an oak floor, and the cellar tank was not renewed during the renovation. Roof cracks: according to the seller caused by work at the neighbours, according to the inspector more likely caused by the foundation. Archive or foundation map: not mentioned.

Advice and costs. The inspector is convinced that the foundation has not been renewed and that the cellar very probably leaks. According to the report, renewing the foundation including the renovation afterwards costs at least € 350,000 (2026 price level). Follow-up investigation or monitoring bolts are not mentioned.

What this shows. A buyer receives a firm conclusion here based on a single floor measurement, without rotation, KCAF category or phase 2.

Case 3: Straight facades, tilted floors and staircase, Amsterdam-Zuid

Situation. Apartment in a building from 1933 with five storeys, owners’ association yes. June 2026. Foundation risk quick scan; the building is presumably part of one structural unit with the buildings to the left.

Findings. Bed joint measurement front facade 18 mm over 6000 mm, rotation 1:333; rear facade 5 mm over 5500 mm, 1:1100; both negligible. Floor levelling 3rd floor: left 50 mm over 9900 mm (1:198), right 51 mm over 10000 mm (1:196), diagonal 62 mm over 11320 mm (1:182), all moderate; front and rear 11 and 12 mm over 5500 mm, negligible. On the 4th floor: diagonal 28 mm over 8400 mm, 1:300, small. The shared staircase falls in KCAF category large, with many cracks.

Advice and costs. Conclusion: moderate risk. Have the stairs and floor joists examined by a structural engineer or specialist firm; a latent foundation defect cannot be ruled out. Check past works through archive research and the multi-year maintenance plan (MJOP). No amounts in the report.

What this shows. Straight facades do not rule out moderately tilted floors and a tilted staircase.

Case 4: Fault line in a poured floor between two parts of a building, Amsterdam-Centrum

Situation. Apartment in a building from 1740 with five storeys, owners’ association yes. January 2026. Foundation risk quick scan. The building shares its foundation with the neighbouring building. The seller reports foundation repair in the front house.

Findings. Floor levelling living room (poured floor, according to the seller from the 1990s, so possibly levelled): approx. 10 cm over 12.5 m between rear right and front left, rotation 1:120, KCAF moderate. At the fault line 1.3 cm over 50 cm, rotation 1:38, very large (structural). The measurement on the underside of the joist floor confirms the slope towards the front left; the fault line widens towards the front facade. Ground subsidence 1.3 mm per year.

Advice and costs. There is presumably a foundation problem in which one part of the building subsides faster than the other; according to the seller an expansion joint was missing. Check the nature and extent of the reported repair through archive research (building permits, deed of division) and the MJOP. No amounts in the report.

What this shows. A fault line shows the difference between parts of a building, even if a poured floor evens out the rest.

Case 5: Foundation plans without proof of execution, Amsterdam-Zuid

Situation. Apartment in a building from 1913 with five storeys, owners’ association yes. In March 2026 we carried out a foundation risk quick scan.

Findings. Floor levelling in the apartment: 29 mm over 5310 mm (rear to front), rotation 1:183, KCAF moderate. Staircase: 6 mm over 900 mm, 1:150, moderate. Bed joint measurement front facade: 4 mm over 4000 mm, 1:1000, negligible. The plasterwork had seams and slight cracks. The archive contained a pile plan, calculations and a geotechnical investigation for a foundation renewal, but no proof of execution. The monitoring bolt in the front facade showed 4.5 mm of subsidence between 24 June 2022 and 15 December 2025. The starting situation is uncertain: that first measurement lies close to the presumed renovation.

Advice and costs. Ask the current owner for a written statement that the foundation has been fully renewed according to the plans. The report does not mention follow-up investigation. No amounts in the report.

What this shows. Plans do not prove execution. As a buyer, you first ask for supporting documents and a statement.

Case 6: Moderate tilt that is not increasing, Amsterdam-West

Situation. Home in a building from 1925 with four storeys and a flat roof, owners’ association yes. In October 2026 we carried out a foundation quick scan investigation. In 2007 an earlier investigation gave foundation code II.

Findings. Bed joint measurement front facade: 13 mm over 8500 mm, 1:653, negligible. Floor levelling across the depth of the home: 71 mm over 7600 mm, rotation 1:107, KCAF moderate (architectural). Practically identical to the 2007 measurement: absolute subsidence over 19 years negligible. No cracks inside or in the front facade. The archive shows a concrete foundation beam with pile caps on timber pile groups. The pile heads lie more than two metres below ground level, the groundwater at around 0.4 m below ground level. No monitoring bolts on the building; the nearest one shows 0.10 mm per year (negligible).

Advice and costs. Foundation risk low, no reason for further investigation. No amounts in the report.

What this shows. A moderate tilt is less worrying if a repeat measurement shows it is not growing. As a buyer, ask about older measurements.

Case 7: Large tilt and diagonal cracks, Amsterdam-Zuid

Situation. Home from 1902, owners’ association no. September 2025: foundation risk investigation phase 0, with leak detection on the roof.

Findings. Bed joint measurement front facade: 40 mm over 4.70 m, rotation 1:117.5, structurally large according to the report. Rear facade, measured at roof height because of a conservatory: 93 mm over 4.70 m, 1:50.5, very large. Floor levelling living room: 21 mm over 4.30 m, 1:204, moderate; rear side 14 mm over 4.30 m, 1:307, small. Side measurements (18 mm and 11 mm) are less reliable because of the staircase, toilet block and possibly levelled floors. Front facade without notable structural cracks, leaning to the left. Rear facade with stepped diagonal cracks. Archive or foundation map: not mentioned.

Advice and costs. The foundation is not in order, which given its age is not exceptional. Place monitoring bolts and measure annually for at least five years. Phase 2 for more certainty, but with a shallow foundation that adds nothing extra. No amounts in the report.

What this shows. A phase 0 shows the tilt, not the speed. As a buyer, you should count on years of measuring.

Case 8: Tilted apartment with its lowest point at the bay window, Amsterdam-Zuid

Situation. Apartment in a building from 1934 with five storeys, owners’ association yes, occupied. March 2026. Foundation risk quick scan; a reason is not stated in the report.

Findings. Bed joint measurement front facade 55 mm over 9700 mm, rotation 1:173; locally 61 mm over 8000 mm, 1:131; rear facade 64 mm over 9300 mm, 1:145; all KCAF moderate. Floor levelling 4th floor: diagonal 68 mm over 13600 mm, 1:200; right side 16 mm, 1:644, negligible. On the 3rd floor: diagonal 88 mm over 14340 mm, 1:162, moderate. Heavy cracks in the front facade, sticking doors and windows, and tilted frames. Archive or foundation map are not mentioned.

Advice and costs. High risk of a foundation defect. Phase 2 is necessary; monitoring bolts can additionally show further subsidence. In line with the report, we advise mapping the severity fully before you take on any obligations. No amounts in the report.

What this shows. KCAF moderate on the measured values can go together with a high-risk verdict once cracks and sticking parts show the same pattern. A buyer then has phase 2 carried out first.

Case 9: Cracks in the staircase despite a negligible facade measurement, Amsterdam-Zuid

Situation. Mid-terrace house from 1922 in a block of 7 homes, five storeys, owners’ association yes (client). April 2026. Foundation quick scan investigation.

Findings. Archive: investigation from 2003; at other building units in the block the foundation has been renewed or repaired, and the archive calls the foundation vulnerable. Division 2003: foundation code 2. One monitoring bolt (1998 to 1999): 1 mm per year, not usable. Bed joint measurement front facade 21 mm over 7200 mm, 1:342, negligible. Floor levelling 1st floor: 18 mm over 10500 mm, 1:583; internal load-bearing wall 28 mm over 5300 mm, 1:189. The 2nd floor gave different values. Staircase: cracks moderate and large; no measurement was taken there in 2003.

Advice and costs. Raised average risk, no clear-cut verdict. Monitoring bolts in the facades and around the staircase, for two to three years. Uniform and at most 1 to 2 mm per year: cause presumably the superstructure. Uneven above 2 mm per year: phase 1 and possibly phase 2. No amounts in the report.

What this shows. Calm facade measurements do not rule out a local problem. A buyer waits here for the monitoring bolts.

Case 10: Foundation code 3 from 2022 adjusted to code 2, Amsterdam-Oost

Situation. Mid-terrace house from 1909 with three storeys and a loft, owners’ association no, occupied. March 2026. Reason: application for a division permit, repeating a phase 1 investigation from 2022.

Findings. Archive: building unit of 8 plots, Amsterdam pile foundation. The 2022 investigation gave rotations between 1:75 and 1:100 on the 1st floor and foundation code 3. Monitoring bolt in the facade: 1.2 mm per year over 16 years, small. Own monitoring bolts, 4 years: less than 1 mm per year. Bed joint measurement front facade 19 mm over 8100 mm, 1:426, negligible. Floor levelling 2026: 1st floor at most 1:132, 2nd floor 1:118, ground floor small and negligible. The 2022 values were not confirmed, and an explanation is missing.

Advice and costs. Foundation is adequate, foundation code 2, no follow-up investigation; the municipality determines the level and the report is valid for six months. No amounts in the report.

What this shows. A single floor measurement can give a heavier code than monitoring bolts and measurements on three floors. A buyer asks for both.

Case 11: Progressively subsiding homes in a building block, Amsterdam-West

Situation. Two mid-terrace houses in a block of four buildings from 1910, four storeys with a loft and basement level, owners’ association yes. February 2025. Basic foundation investigation commissioned by the owners’ association. A resident had bought a renovated home three years earlier; the damage appeared afterwards.

Findings. Archive: Amsterdam pile foundation, pile heads far below the groundwater, ground subsidence at the rear facade on average 5.7 mm per year. Foundation code 2 in 2003. Bed joint measurement front facade 21 mm over 8500 mm, 1:404, negligible. Floor levelling 1st floor: 176 mm over 10300 mm, 1:58, very large; rear facade 104 mm over 7820 mm, 1:75. Other home: 137 mm over 7930 mm, 1:57. On average 5.4 mm per year since 2003. Cracks moderate to large, sticking doors.

Advice and costs. Insufficient; structural damage within 5 years, repair necessary. Start immediately, quotes from several parties. If in doubt, phase 2, around € 10,000 (2025 price level). No repair amount in the report.

What this shows. A negligible facade measurement hides serious floor rotations here. So a buyer also looks at the floors.

Case 12: Moderate foundation with subsidence of 2.8 mm per year, Amsterdam-West

Situation. Mid-terrace house from 1903 in a block of four buildings, four storeys with a loft, owners’ association yes. September 2025. Brief phase 1 investigation commissioned by the owners’ association.

Findings. Archive: Amsterdam pile foundation; the block received quality level III, this home level II. Absolute subsidence 0.21 m (0.80 laid, 0.59 measured). Monitoring bolt front facade 2000 to 2006: 1 mm per year. Bed joint measurement front facade 14 mm over 4500 mm, 1:321, negligible. Floor levelling: 101 mm over 12,000 mm, 1:118; front facade width 41 mm over 4300 mm, 1:105; both moderate. Around the staircase, rotations below 1:75, attributed to the joist floor. Up to 70 mm more subsidence, on average 2.8 mm per year. Little damage.

Advice and costs. Condition moderate; repair in due course. Monitoring bolts for 1 to 3 years: below 2 mm per year no action, above 2 mm per year phase 2. No amounts in the report.

What this shows. The absence of damage says little about subsidence that continues. A buyer asks for the monitoring bolt series.

Case 13: Building rotating forwards without cracks, De Pijp

Situation. Mid-terrace house from 1896 in a unit of 3 homes, five storeys with a loft and basement level, owners’ association yes. June 2026. Purchase; building inspection with foundation risk quick scan (only this part is used here).

Findings. Archive: Amsterdam pile foundation; basement level and extension on steel tubular piles in 2002. Monitoring bolt front facade, 23 years: 1.7 mm per year, small. Division 2004: foundation code II despite rotations below 1:200, advice missing. Bed joint measurement front facade 18 mm over 5000 mm, 1:277, small. Floor levelling 100 mm over 11400 mm, 1:114, moderate, about 30 mm more than the previous measurement. No cracks or defects in the structure.

Advice and costs. Possibly active subsidence at the front, partly historical. First request the phase 2 investigation of the neighbouring building (shared foundation); otherwise monitoring bolts, for at least three years. No amounts for the foundation in the report.

What this shows. Subsidence and a clean structure can go together. A buyer gets no conclusive answer here and has to wait for the follow-up investigation.

11. Frequently asked questions about foundation investigation when buying

Should I have a foundation investigation done for a house in Amsterdam?

Our advice is yes for every house built before 1970. Until about that time, Amsterdam was mostly built on timber piles. The year of construction says something about the type of foundation, not about its condition.

What does a foundation quick scan cost?

We carry out the quick scan (phase 0) during the building inspection. Inspection and quick scan together cost from € 898 including VAT; the quick scan itself then costs € 399. You will have the report within two working days.

What is the difference between phase 0, phase 1 and phase 2?

Phase 0 is a quick scan during the inspection: measuring bed joints and levelling floors. Phase 1 is a more extensive investigation above ground, possibly with archive research. In phase 2 the foundation is dug open and the piles themselves are examined, possibly with wood samples.

Is the foundation label in the valuation report enough?

No. The label from A to E is a risk indication based on visible signs and online data. It is not a foundation investigation and says nothing definitive about the condition of the piles.

The seller says the foundation has already been repaired. Is that enough?

Ask for the repair report, the drawings, the permit and any warranty. Without those documents we cannot establish that the foundation has been renewed. Measurements after a renovation only show the tilt since that renovation.

Does a foundation investigation fit within my purchase condition?

A quick scan does, since we do it during the inspection. A phase 2 investigation takes about one and a half to two months from order to report. That often does not fit within a purchase condition of a few weeks; discuss this before you bid.

Who pays for foundation repair in an apartment?

The owners’ association, and each owner contributes in proportion. Before buying, ask about earlier foundation investigations, monitoring bolt data, the minutes and the reserve fund of the owners’ association. We do not give legal advice.

What does foundation repair cost?

In Amsterdam from € 2,500 per m², from € 3,500 per m² with a cellar, and then finishing work from € 3,000 per m² (2025 price level). We do not quote a total amount, because the differences between buildings are large.

Do you recommend a foundation repair company?

No. Premiumkeur does not recommend foundation repair companies or contractors, so that we have no interest in the repair. With our report you can have several parties quote for the same work.

Do you also inspect for the seller?

No. We work only for buyers and owners.

12. Videos of our foundation investigation

On the Premiumkeur YouTube channel you can see our inspectors at work, including bed joint measurements, floor levelling and in crawl spaces.

13. Further reading

• Building inspection Amsterdam knowledge base: the building inspection, the purchase contract and buying in Amsterdam.
• Mold and damp Amsterdam: when damp in a cellar or basement level is the problem.
• Services and rates (in Dutch).

Sources: the cases on this page come from Premiumkeur’s own reports (2025 and 2026). Addresses and names have been left out. Prices and practical figures according to Premiumkeur, October 2026. External sources: RVO, Funderingsproblematiek; Ministry of the Interior and Kingdom Relations (BZK), Nieuw taxatierapport: fundering eindelijk volwaardig onderdeel (1 April 2026); Rijksoverheid, rights for doorstep sales. Reference date: October 2026.

Contact details Premiumkeur Amsterdam

Premiumkeur B.V., Heiligeweg 30, 1012 XR Amsterdam
Phone: +31 20 773 6842
Email: premiumkeur@gmail.com
Chamber of Commerce (KvK) 81106130

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