Knowledge base foundation investigation phase 1

This knowledge base is based on almost 2,900 of Premiumkeur’s own reports from 2013–2026: building inspections, foundation surveys, roof, damp and crawl space inspections and maintenance plans.

In brief. In a phase 1 foundation investigation (in Dutch: funderingsonderzoek fase 1) we investigate the foundation without digging. We measure whether the facades and floors have settled, calculate how far the building leans, look at cracks and search the archive for drawings, earlier foundation investigations and repairs next door. That leads to an assessment of the risk and advice: do nothing, install levelling bolts, or a phase 2 investigation in which the piles are dug up. Phase 1 at Premiumkeur costs € 699 including VAT for a standard home, and up to € 1,499 or more for a large home, several buildings or a complex investigation. Choose the inspector yourself, and do not let the estate agent steer that choice.

Lees deze kennisbank in het Nederlands

1. What is a phase 1 foundation investigation?

Phase 1 is the above-ground foundation investigation. We do not see the foundation itself; we assess it through what happens above it. If a house has settled unevenly, you see it in sloping mortar joints, sloping floors and cracks.

Phase 1 is more thorough than the quick scan (phase 0) we do during a building inspection. We measure in more places and on more floors, convert the lean into a rotation and do archive research. Phase 0 is only available together with an inspection; without one, phase 1 is the first step.

One caveat that is in all our reports: a building can stand straight while the foundation is still poor. Phase 1 gives a good picture of the risk, not certainty about the piles. Only phase 2 gives that. And every foundation investigation is a snapshot. We give no guarantees for the future, because a foundation can deteriorate quickly for various reasons, for example a falling groundwater level, dewatering or building work nearby.

2. When is phase 1 useful?

• You are buying an old house in an area with wooden pile foundations and want to know how big the risk is.
• You see cracks, sloping floors or sticking doors and want to know whether the foundation is the cause.
• You want to know whether a more expensive phase 2 investigation is needed.
• Your neighbours are about to repair their foundation and you want to know what that means for your home.
• An owners’ association (VvE) wants a picture of the whole building.

3. What we do in phase 1

1. Archive research. We look for the year of construction, original drawings, a pile plan, earlier foundation repair and permits in the same block, and earlier foundation inspections or foundation codes. We also look at the municipality’s levelling-bolt data. Separate archive research at the municipality costs from € 199. If you choose a very extensive phase 1 investigation, that archive research is already included in the price.
2. Mortar-joint measurement. With a laser level we measure, per facade, how a continuous horizontal joint runs from party wall to party wall. Size differences in the bricks can cause up to about 7 mm deviation. If there is reason to during the inspection, we also measure how far a facade leans out of plumb (plumb measurement). That is not a standard part of every phase 1.
3. Floor levelling. We measure the floors along the party walls, on several floors. An old wooden floor is never completely flat; that gives 10 to 20 mm inaccuracy. A lean on one floor can also be rot in the joists; sloping floors on several floors point more to the foundation.
4. Calculating the rotation. From the measurements we convert the settlement difference into a rotation: the difference divided by the distance, such as 1 : 200.
5. Visual inspection. Facades, interior walls, frames and doors, with an analysis of the cracks: where they are, which way they run and whether they were repaired before.
6. The neighbours. If the neighbours’ foundation has already been renewed, your building can start to "hang" or become a hinge building. We take that into account.

We are on site for 1.5 to 2.5 hours. You receive the report within 5 to 10 working days after your payment has been received.

4. How we assess the lean

For the rotation we use the classification from the guideline of KCAF (the Dutch knowledge centre for foundation problems). Premiumkeur is not affiliated with KCAF, but works according to the KCAF guideline. Several Premiumkeur inspectors have completed the KCAF training.

A one-off measurement shows how far the building leans now, not how fast it is settling. You can only measure that with levelling bolts, over at least two to three years. On average a building in Amsterdam settles about 1.5 mm a year; above 2.5 to 3 mm a year it is a concern.

Piles drying out is rare in Amsterdam. The heads of the foundation piles are usually more than 2.5 metres below ground level, while the groundwater in Amsterdam is on average 80 to 90 centimetres below ground level. There are exceptions, but in most cases the pile heads of Amsterdam foundations do not dry out.

5. What can follow phase 1

• Nothing. No notable settlement and no damage pointing to the foundation.
• Levelling bolts. At least eight, on the front facade, rear facade and party walls. After two to three years you know how fast the building settles. Bolts on the front facade only give an incomplete picture.
• Phase 2. The piles are dug up and examined up close. That is also needed for a foundation code, for example when splitting a property in Amsterdam. Read more in the knowledge base foundation investigation phase 2.
• A structural engineer straight away. With active, serious settlement, safety comes first; sometimes temporary props are needed.

6. Choose your own independent inspector

Do not let the estate agent steer your choice of inspector. An estate agent is usually only paid once the house is sold. An inspector who gets work through estate agents can end up in a difficult position. The risk is that a foundation defect is played down, or described so cautiously that the sale still goes ahead. That is far from true of every inspector, and an estate agent may mean well. But you cannot tell from the report itself.

So choose an inspector yourself who does not work with estate agents, and ask beforehand whether they receive assignments or commission from estate agents. Premiumkeur does not work with estate agents, financial advisers or contractors.

7. Case studies from our reports

The cases are anonymous: no addresses, no names.

Case 1: neighbour already repaired, apartment complex in De Pijp, May 2024

• Situation: building from 1893 with five storeys and a VvE. According to the 1892 drawings an Amsterdam pile foundation; the neighbouring building in the same block had its foundation renewed around 2010.
• Findings: the rear facade had settled 42 mm to the left, the floors up to 54 mm. Rotation of the rear facade 1 : 119. Cracks in the party wall in the stairwell and around the rear windows.
• Advice: levelling bolts on all facades and party walls and measure for two to three years; for a direct judgement, phase 2.
• Why it matters: because the neighbouring building already has a new foundation, this building can start to "hang".

Case 2: old foundation code expired, apartment complex in the Kinkerbuurt, August 2024

• Situation: building from 1888 with five storeys and a VvE. Around 2003 the municipality gave it foundation code III (moderate). Since then the block has had foundation repair three times.
• Findings: up to 84 mm height difference between the rear extension and the main building. Rotation of the rear extension 1 : 82 (large), of the whole building 1 : 148 (moderate). Sticking windows and crooked frames.
• Advice: the term of the old code had expired. Levelling bolts or phase 2 straight away. Repair estimated at € 150,000 excluding finishing (2024 prices).
• Why it matters: an old foundation code is a snapshot; after fifteen years it says little.

Case 3: empty commercial building leaning backwards, Amsterdam-Centrum, April 2024

• Situation: six-storey building from 1936, probably on an older foundation. No drawings or pile plan in the archive.
• Findings: 149 mm difference between front and rear facade, rotation 1 : 104. In the basement concrete damage, rusting steel beams and fungus.
• Advice: splitting requires a foundation inspection, so phase 2.
• Why it matters: phase 1 shows whether phase 2 is needed, and where to dig.

Case 4: farmhouse on a shallow foundation, Abcoude, October 2023

• Situation: detached farmhouse from 1680 on a shallow foundation (no piles).
• Findings: the upper floor sloped more than 220 mm. Filled cracks reopened and windows stuck again after planing.
• Advice: foundation repair, first a structural engineer and soil investigation. Repair and finishing estimated at at least € 300,000 (2023 prices).
• Why it matters: with clear, active damage, phase 1 can be enough to advise repair.

Case 5: corner house with a settled front facade, Utrecht, February 2023

• Situation: corner house from 1940 with three storeys.
• Findings: the right side of the front facade was 44 mm lower than the left. A crack that had been repointed before, and several heavy facade cracks next door.
• Advice: renew the foundation, or first measure longer with levelling bolts.
• Why it matters: look at the houses in the street too. If the neighbours settle as well, it is no coincidence.

Case 6: Floor more than 12 cm out of level and cracks in the front facade, Amsterdam-Zuid

Situation: Apartment building from around 1905, five storeys, used for housing and commercial space, with an owners’ association (VvE). The client wanted to know the condition of the foundation. Above-ground foundation survey (phase 1) in March 2019.

Findings:

• Floor levelling on the 2nd floor: a height difference of more than 12 cm.
• Bed joint measurement on the front facade: the bed joint is not level.
• Several substantial subsidence points and cracks in the front facade brickwork; one vertical crack gets wider from bottom to top.
• Above the right-hand window frame there is a real chance of a brick falling; a direct safety risk.
• The stone window sill is clearly tilted, with subsidence beneath the frame.

Advice: Have the brickwork above the window frame repaired as soon as possible. We rated the foundation as poor; foundation repair is unavoidable in the longer term. We advised the VvE to commission a foundation inspection in which the timber piles are assessed up close, or, as a cheaper step, to install settlement bolts to see how many millimetres a year the building is sinking.

Why it matters: Here the floor survey, the bed joint and the facade cracks all pointed the same way. That made a clear verdict possible, and safety on the street came first.

Case 7: Renovated townhouse: level floors don’t tell the whole story, Amsterdam-Zuid

Situation: Townhouse from 1895, five storeys, no owners’ association, fully renovated in the past, with a rear extension and a cellar. The client wanted to know the condition of the foundation before signing the purchase contract. Above-ground foundation survey (phase 1) in January 2021.

Findings:

• Floor levelling with a construction laser on several floors: floors level to within 1 cm.
• At the bathroom (probably on the third floor) the floor has dropped more than 3 cm, possibly due to a structural defect.
• Bed joint measurement on the front facade: level. The rear facade is rendered and could not be measured.
• A substantial crack in the rear facade, probably caused when the extension was built, or because the extension is subsiding.
• Cellar: no cracks, but penetrating damp.

Advice: Go through the building drawings to check whether floors and joists were levelled during the renovation. Hold off signing until it is confirmed that the extension stands on concrete or steel piles, and have the building and structural drawings reviewed. We rated the foundation as reasonable, given the age of the timber piles.

Why it matters: After a major renovation a floor may have been levelled while the building itself has settled. A measurement only means something once you check the archive drawings as well.

Case 8: Front facade only 9 mm out, the problem is in the extension, Amsterdam-West

Situation: Ground-floor flat in an apartment building from around 1890, five storeys, with an owners’ association (VvE) and a later rear extension. The client wanted to know the condition of the foundation. Above-ground foundation survey (phase 1) in July 2019.

Findings:

• Floor levelling with a laser: living room and first floor practically level.
• The tiled floor in the hallway is clearly uneven; this is a structural issue, not a foundation defect.
• Bed joint measurement on the front facade: a deviation of 9 mm, remarkably little for a building from 1890.
• Front and rear facades without cracks or subsidence.
• The brick column at the rear right of the extension has subsided and is unstable; the extension probably has no foundation. The double glazing in the glazed frame cracked because of that local subsidence and because the glass was not fitted professionally (no glazing sealant).

Advice: Remove the hallway floor and install new floor joists. We rated the foundation of the main building as good, with the caveat that this is a snapshot and timber pile foundations have a limited lifespan.

Why it matters: An uneven floor or cracked glass does not always mean a bad foundation. Measuring made it possible to separate the local problem at the extension from the main building.

8. Cost and booking

Phase 1 at Premiumkeur costs € 699 including VAT for a standard home. For a large home, several buildings or a complex investigation the price rises to € 1,499, sometimes more. Complex means that structural investigation is also needed and files have to be reviewed. An example: a small detached house usually falls under the standard price of € 699. A listed canal house with a front house and a rear house (in Dutch: voorhuis and achterhuis) needs far more measurements, more archive work and often structural investigation, so it falls in the higher price range. The same applies to an owners’ association (VvE). A VvE with one house number is one building. A VvE with several house numbers is still one VvE, but it consists of several blocks of houses. Then there is much more to measure and investigate, so that investigation also falls in the higher price range. We also investigate commercial buildings in Amsterdam. They are often large, so the price is higher than the € 699 for a standard home. At the standard price, archive research at the municipality costs from € 199 extra. If you choose a very extensive phase 1 investigation, it is included and you do not pay for it separately: an all-inclusive price. A report in English costs € 100 extra. All prices are on our services and rates page (in Dutch); more about the service on Foundation inspection Amsterdam.

Want to book? Call Premiumkeur on +31 20 773 6842, send a WhatsApp to +31 6 2956 3190 or email premiumkeur@gmail.com. We can be reached by WhatsApp and email 7 days a week.

Buying an older building? You can combine the foundation risk check with the building survey itself: see Pre-Purchase Building Survey Amsterdam, or Property Inspection Amsterdam if you are buying as an investor.

Frequently asked questions

What does a phase 1 foundation investigation cost?

At Premiumkeur € 699 including VAT for a standard home. For a large home, several buildings or a complex investigation, with structural investigation and a review of files, it rises to € 1,499, sometimes more. Archive research at the municipality costs from € 199 extra, except with a very extensive phase 1 investigation: then it is included in the price.

Can I use the inspector the estate agent recommends?

You can, but it is wiser to choose an independent inspector yourself. An estate agent is usually only paid once the house is sold. An inspector who gets work through estate agents may be more inclined to play down a foundation defect. Always ask whether the inspector works with estate agents.

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

Phase 0 is a quick scan during the building inspection. Phase 1 is more thorough, with more measurements, a rotation calculation and archive research. In phase 2 the piles are dug up.

Is there any digging in phase 1?

No. Everything happens above ground.

Will I know for certain after phase 1 how my foundation is doing?

No. Phase 1 gives a good picture of the risk. Only phase 2 gives certainty about the piles.

What does a rotation of 1 : 100 mean?

A difference of 1 per 100 in length, so 10 mm per metre. From 1 : 100 the KCAF guideline speaks of possible structural damage.

How long does phase 1 take?

We are on site for 1.5 to 2.5 hours. We send the report within 5 to 10 working days after your payment has been received.

Do I get a foundation code after phase 1?

No. A foundation code is only given after a phase 2 investigation.

Do you give a guarantee on the foundation?

No. A foundation investigation is a snapshot. A foundation can deteriorate quickly for various reasons, for example a falling groundwater level or building work nearby.

Do foundation piles in Amsterdam dry out?

Rarely. The pile heads are usually more than 2.5 metres below ground level and the groundwater on average 80 to 90 centimetres below ground level. There are exceptions, but the heads usually stay under water.

Sources

• Foundation investigation: from QuickScan to Phase 1 and Phase 2 – KCAF (in Dutch)
• Guideline for investigating foundations under buildings – KCAF (copy at the municipality of Woerden, in Dutch)
• Premiumkeur’s own phase 1 foundation reports, 2022 to 2024