Foundation investigation in Amsterdam: knowledge base

This knowledge base explains what you need to know about foundation investigations in Amsterdam: why foundations here are a risk, which types of investigation exist, how measurements are taken, what the foundation codes mean, what investigation and repair cost, and what to look out for when you buy a home. The information is based on the daily practice of Premiumkeur Funderingsonderzoek in Amsterdam. Premiumkeur has an average rating of 4.9 stars from 698 Google reviews and 100 Trustpilot reviews.

In short: many Amsterdam homes stand on wooden piles. A foundation risk investigation (phase 0) costs € 399 including VAT when combined with a building inspection, and you receive the report within 2 working days. A phase 1 investigation costs € 699 to € 1,499; a phase 2 investigation costs on average € 3,000 to € 4,000 excluding excavation. Foundation repair in Amsterdam costs roughly € 2,000 to € 2,500 per square metre, excluding the renovation afterwards.

Why foundations in Amsterdam are a risk

Most older houses in Amsterdam stand on wooden piles. Wood has a limited lifespan: wooden piles last about 90 years on average, but that can be shorter because of:

• a low groundwater level, which leaves the pile heads dry so they start to rot;
• bacteria that attack the wood, even under water;
• leaking main sewers that lower the groundwater level locally;
• overloading of the piles, for example by an extra storey or a renovation.

Signs of foundation problems

Common signs are sloping floors, cracks in façades and interior walls, and windows and doors that stick. A sloping floor on one storey can also have another cause, such as rot in the floor joists. When floors on several storeys slope in the same direction, a foundation problem is more likely.

Types of foundation investigation: phase 0, phase 1 and phase 2

Foundation risk investigation phase 0 (quick scan)

A phase 0 foundation risk investigation is a quick assessment without excavation, carried out during the building inspection. The inspector carries out a floor levelling survey and a masonry joint measurement, inspects the façades and interior walls and analyses cracks. This tells you how the foundation is doing before you sign the purchase contract.

Foundation investigation phase 1

A phase 1 foundation investigation is more extensive and follows the KCAF guideline. Besides the measurements, archive research can be done at the municipality for building drawings and earlier foundation reports. Phase 1 is also used as an exploratory investigation when a building is to be split into apartments.

Foundation investigation phase 2

In a phase 2 investigation the wooden pile foundation is exposed through an inspection pit of about 2.5 by 2.5 metres and 2 to 3 metres deep. The piles and the wood are inspected directly, if necessary with laboratory testing of wood samples. A foundation code can only be assigned after a phase 2 investigation. A phase 2 investigation is required for a permit to split a building in Amsterdam.

How the measurements work

Floor levelling survey

In a floor levelling survey (vloerwaterpassing) the inspector uses precise measuring equipment on several storeys to determine how much the floors slope. It is not a separate service, but part of a phase 0 or phase 1 investigation.

Masonry joint measurement

In a masonry joint measurement (lintvoegmeting) the horizontal course of a continuous mortar joint in the façade is measured. Because that joint was laid level when the house was built, its course shows whether and how the façade has settled. Together with the floor levelling survey this gives a good indication of whether a home is subsiding. On a rendered façade a joint measurement is not possible; the inclination of the walls is measured instead.

Crack analysis and archive research

Cracks in façades and interior walls are mapped and assessed by pattern and direction. Archive research at the municipality looks for building drawings and earlier foundation reports.

Measuring bolts: determining the rate of subsidence

Measuring bolts (meetbouten) are stainless steel bolts of 6 mm that are fixed about half a metre above ground level in the façade and the party walls, usually 8 to 10 per building. They are measured against a fixed reference point. The first measurement is the zero measurement; by measuring again later (usually once a year) the rate of subsidence is determined to a tenth of a millimetre.

• The average rate of subsidence in Amsterdam is about 1.5 mm per year.
• A rate above 2.5 to 3 mm per year is a cause for concern.
• After 2 to 3 years of measuring it is usually clear whether the foundation is in order.
• Measuring bolt data older than 10 years is unreliable, and a proper assessment needs bolts on all walls (front and rear façade and both party walls).

Foundation codes 1 to 4

After a phase 2 investigation a foundation receives a foundation code:

• Code 1: the foundation is very good; it is new or has been renewed.
• Code 2: the foundation is good; minor but acceptable damage is expected within 25 years.
• Code 3: the foundation is reasonable; damage is expected within 10 to 15 years.
• Code 4: the foundation is poor; repair is necessary within 0 to 10 years.

Note: a foundation code is a snapshot and may be 10 to 20 years old. Because wooden piles deteriorate gradually, the current condition may be worse than the code suggests. When a building in Amsterdam is split, code 3 or 4 means the foundation must be renewed; with code 2 this is not required.

What does a foundation investigation cost?

Current prices are listed on the Dutch page Diensten en tarieven.

What does foundation repair cost in Amsterdam?

Foundation repair is drastic and expensive, partly because contaminated Amsterdam soil has to be removed by truck and basements need a thick watertight concrete structure. Indicative amounts:

• foundation repair: € 2,000 to € 2,500 per m²;
• renovating the ground floor after the repair: € 2,000 to € 2,500 per m²;
• building permit, drawings and structural calculations: € 10,000 to € 15,000;
• adding a basement: € 2,500 to € 3,000 per m² for excavation, plus € 1,500 to € 2,500 per m² to finish the basement;
• removal of extra contaminated soil: up to € 30,000.

For a house of about 80 m² the total comes to more than € 300,000. Repair and renovation take 6 to 8 months on average. Residents usually have to move out temporarily; moving and storage cost about € 20,000, and buyers of a ground-floor apartment may face up to 12 months of double housing costs.

How long does a foundation investigation take?

• Phase 0: about 1.5 hours, together with the building inspection; you receive the report within 2 working days.
• Phase 1: about 2.5 hours on site; reporting according to the KCAF guideline takes about a week.
• Phase 2: the on-site inspection takes about 2 hours, but because of the excavation the whole process from order to report takes 1.5 to 2 months on average.

Foundation investigation when buying a home

For a home on wooden piles it is wise to have the foundation investigated before you sign the purchase contract, or within the period of a building inspection condition (ontbindende voorwaarde). The outcome helps you decide whether to buy, to negotiate the price and to estimate future costs. A phase 0 investigation during the building inspection is the fastest route.

Confidentiality of the foundation report

Some inspection companies store foundation data in a shared database, such as that of the Nationale Alliantie Fundering Onderzoek (NAFO), to which parties in the property chain can also have access. At Premiumkeur the foundation report is confidential: we share it only with the client and never with third parties without permission.

Questions to ask any foundation investigator

• Do you carry out both a floor levelling survey and a masonry joint measurement?
• Do you work according to the KCAF guideline?
• Do you work with estate agents, valuers or repair companies, or do you receive referral fees?
• Who will the report be shared with?
• What is excluded from the investigation, and what happens if something cannot be measured?

Pre-construction survey when work is done nearby

Are your neighbours repairing their foundation, is a basement being built, or is there demolition or pile driving? Have a pre-construction survey (nulmeting) carried out before the work starts. It records the condition of your home, so that you can later prove that new damage was caused by the work. Premiumkeur follows the NIVRE guidelines for this. If you have your own foundation repaired, we also advise a survey of the neighbouring buildings.

About Premiumkeur Funderingsonderzoek

Premiumkeur Funderingsonderzoek is part of Premiumkeur B.V. (Chamber of Commerce 81106130), an independent building consultancy in Amsterdam. We do not work with estate agents, valuers, mortgage lenders, financial intermediaries, contractors or foundation repair companies, and we do not carry out foundation repairs ourselves. Premiumkeur is NHG-recognised and NEN 2767 certified, works according to NTA 8060 and carries out foundation investigations according to the KCAF guideline. More information in English: Foundation investigation Amsterdam: information and reviews in English. The Dutch version of this knowledge base: Kennisbank funderingsonderzoek Amsterdam.

Frequently asked questions about foundation investigations in Amsterdam

How much does a foundation investigation cost in Amsterdam?

A phase 0 foundation risk investigation costs € 399 including VAT when combined with a building inspection. A phase 1 investigation costs € 699 to € 1,499 and a phase 2 investigation on average € 3,000 to € 4,000 excluding excavation.

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

Phase 0 is a quick assessment without excavation during the building inspection. Phase 1 is a more extensive investigation according to the KCAF guideline, optionally with archive research. In phase 2 the wooden pile foundation is exposed and inspected; only then can a foundation code be assigned.

How long do wooden piles last?

Wooden piles last about 90 years on average. A low groundwater level, bacteria, leaking sewers and overloading can shorten that lifespan.

What is a normal rate of subsidence in Amsterdam?

On average Amsterdam homes subside about 1.5 mm per year. A rate above 2.5 to 3 mm per year is a cause for concern. This is determined with measuring bolts.

What does foundation code 3 mean?

Foundation code 3 means the foundation is reasonable, but damage is expected within 10 to 15 years. When a building in Amsterdam is split, a foundation with code 3 or 4 must be renewed.

How much does foundation repair cost in Amsterdam?

Foundation repair costs roughly € 2,000 to € 2,500 per m², plus € 2,000 to € 2,500 per m² for the renovation afterwards and € 10,000 to € 15,000 for permits and drawings. For a house of about 80 m² this comes to more than € 300,000.

How quickly do I receive the report?

For a phase 0 investigation you receive the report within 2 working days. Phase 1 reporting takes about a week; a phase 2 process takes 1.5 to 2 months on average from order to report.

Is my foundation report shared with others?

Not at Premiumkeur. The foundation report is confidential and is shared only with the client, never with estate agents, valuers, banks or a database without your permission.

Contact details Premiumkeur Funderingsonderzoek

Premiumkeur B.V.
Assendelftstraat 180
1013 SP Amsterdam
Phone: +31 20 773 6842
Email: premiumkeur@gmail.com
Chamber of Commerce (KvK): 81106130

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