Knowledge base foundation investigation phase 2
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 2 foundation investigation (in Dutch: funderingsonderzoek fase 2 or 2e fase funderingsonderzoek) the wooden pile foundation is dug up. A specialist company digs an inspection pit down past the pile heads, and our inspector examines and measures the piles, the cross beam (kesp) and the longitudinal beam (langshout) up close. It is the only way to establish the condition of the piles themselves, and in Amsterdam the only way to get a foundation code. Phase 2 at Premiumkeur costs from € 3,000 excluding VAT, plus the digging (on average € 4,000 to € 8,000) and, if needed, wood samples (about € 700). From order to report takes on average one and a half to two months. Choose the inspector yourself, and do not let the estate agent steer that choice.
1. What is a phase 2 foundation investigation?
Phase 2 is the underground part of a foundation investigation. In phase 0 and phase 1 we only look above ground: we measure the horizontal mortar joints, level the floors and look for cracks. That gives an estimate of the risk. It does not show the condition of the piles.
In phase 2 we do dig. The foundation is exposed and physically checked, which is why it is called a destructive investigation. It gives the most certain result there is.
Our own reports put it this way: the only way to assess a wooden pile foundation directly is a phase 2 investigation in which the piles and the structure above them are exposed.
2. When do you need phase 2?
- After phase 0 or phase 1 shows a high risk. If the measurements above ground show that the foundation has settled considerably, phase 2 is the next step.
- When splitting a property in Amsterdam. In many cases the municipality asks for a phase 2 report with the application for a splitting permit. If the foundation has already been renewed, no investigation is needed.
- If you need a foundation code. A foundation code is only given after a phase 2 investigation.
- Before foundation repair. The report is the basis for a repair plan and for quotes.
Phase 2 is not always the best first step. Sometimes it is wiser to measure for a few years first with levelling bolts (in Dutch: meetbouten). At least eight bolts are needed. Many houses only have bolts on the front facade, which does not give a full picture.
3. Phase 0, phase 1 and phase 2 compared
| Part | Phase 0 (quick scan) | Phase 1 | Phase 2 |
|---|---|---|---|
| What | Mortar-joint measurement, floor levelling and inspection during the building inspection | More extensive measurements and reporting above ground, optionally with archive research | Dig an inspection pit, inspect and measure piles, cross beam and longitudinal beam |
| Digging | No | No | Yes |
| Price at Premiumkeur | € 399, only together with the building inspection (together from € 898 incl. VAT) | € 699 to € 1,499 incl. VAT | From € 3,000 excl. VAT, plus digging and any wood samples |
| Outcome | Risk estimate | More detailed risk estimate and advice | Condition of the piles, advice on keeping or repairing, foundation code |
More about the first two steps in our foundation investigation knowledge base and on Foundation inspection Amsterdam. Phase 1 is explained step by step in the knowledge base foundation investigation phase 1.
4. How a phase 2 investigation works
- Choosing the spot. We prefer to dig at the wall with the most settlement or the highest risk. With a detached or corner house this can sometimes be done from outside, for example in the garden. Otherwise it is done inside, in the living room or basement.
- Digging. A specialist company digs the inspection pit. Inside a home it is about 2.5 by 2.5 metres and on average 2 to 3 metres deep. If no digger can get in, it is dug by hand. Premiumkeur can arrange the digging for you; you may also choose a company yourself.
- Inspecting. Our inspector goes into the pit and examines the piles, the cross beam and the longitudinal beam. With an impact hammer (De Specht) we measure how deep a pin penetrates the wood. The deeper, the softer and weaker the wood. We measure the pile diameter and check whether the piles are properly under the wall.
- Groundwater. We record the groundwater level relative to the top of the foundation timber. Wood that stays under water cannot dry out and rot through fungi.
- Wood samples. If the municipality requires it or the measurements call for it, we take wood samples from the piles. A laboratory examines them for bacterial decay.
- Report. You receive a report with photos, measurements, an assessment of the foundation and advice. From order to report takes on average one and a half to two months.
Our YouTube channel has a video of a phase 2 foundation investigation (in Dutch).
5. What we look at in the pit
We work according to the guideline of KCAF (the Dutch knowledge centre for foundation problems). A few points from it, so you know what happens:
- The pit. At least 0.7 metres wide, and the pile heads must be exposed by at least 0.4 metres.
- Number of piles. For a building of more than three storeys at least three piles or three pile pairs are examined, for lower buildings two.
- Impact measurements. At least three measurements per pile, about 15 cm below the longitudinal beam or cross beam. The cross beam and longitudinal beam are measured too.
- Groundwater. If the groundwater is more than 20 cm above the top of the foundation timber, that counts as sufficient. Between 5 and 20 cm is small, less than 5 cm insufficient.
- Wood testing. How much the wood is decayed decides whether samples are needed. With limited decay they are recommended; if the decay could become structural they are necessary.
The final verdict is a colour: green (sufficient), orange (not conclusive) or red (insufficient or poor). In Amsterdam phase 2 also leads to a foundation code from 1 to 4. With code 3 or 4 the foundation must be renewed when splitting a property, with code 2 it does not.
In Amsterdam we almost never see piles drying out, because the groundwater is high. What we do see is bacterial decay. That also happens under water and can affect a pile along its whole length. We also find rot on pile heads and cross beams, and piles placed too shallow or next to the wall.
6. What does phase 2 cost?
| Part | Price |
|---|---|
| Inspection and report by Premiumkeur | from € 3,000 excl. VAT |
| Digging the inspection pit (specialist company) | on average € 4,000 to € 8,000 |
| Wood samples with laboratory testing, if needed | about € 700 |
The digging depends on the location, the depth and the groundwater. If digging has to happen in the street or water has to be pumped away, it costs more.
For comparison: foundation repair in Amsterdam costs from € 2,500 per m², with a basement from € 3,500 per m², plus finishing. Examples on our site involved repair costs of at least € 100,000 and € 160,000. A phase 2 investigation is a small cost compared with what is at stake.
All prices are on our services and rates page (in Dutch).
7. Case studies from our reports
The cases are anonymous: no addresses, no names.
Case 1: pile next to the wall, apartment building in the Jordaan, April 2019
- Situation: building from around 1900 with four storeys and an owners’ association (VvE). A year earlier our phase 1 investigation had already shown considerable settlement, especially on the first floor with very sloping floors.
- Findings: one pile stood more than 16 cm beside the wall. With a pile diameter of 23 cm, only 7 cm of pile was left under the wall, and the wall had settled badly there. The longitudinal beam under the wall was seriously decayed, sagging and broken in several places. At several front-facade piles the pin of De Specht reached the maximum of 50 mm. The extension turned out to have no foundation at all.
- Advice: the foundation had been in very poor condition for decades. Foundation repair was necessary.
- Why it matters: above ground you saw sloping floors. Only in the pit did it become clear that the piles themselves were the problem.
Case 2: phase 1 with advice for phase 2, apartment complex in Amsterdam-Oost, March 2024
- Situation: building from 1905 with five storeys and a VvE.
- Findings: uneven settlement with a difference of more than 70 mm. An old investigation from 2002 showed hardly any difference. If that was correct, the difference had grown by about 3 mm a year.
- Advice: first measure for two to three years with levelling bolts. A direct judgement on the piles needs phase 2.
- Why it matters: phase 1 shows whether there is a problem. Phase 2 shows how big it is.
Case 3: neighbours about to repair, terraced house in the Jordaan, May 2024
- Situation: early twentieth-century house in a row of three, with no pile plan in the archive.
- Findings: the front facade had settled 40 mm to the right, the whole row 148 mm. The neighbouring house was about to have its foundation repaired, and the party wall was possibly shared.
- Advice: have the foundations separated to limit damage. Whether a party wall is shared can only be established by destructive investigation.
- Why it matters: with a shared party wall, your neighbours help decide what happens to your foundation.
Case 4: One of four buildings out of level: settlement bolts instead of guesswork, Amsterdam
Situation: Apartment complex from around 1890, made up of four adjoining buildings with five storeys, occupied, no owners’ association. The client wanted to know the condition of the foundations of the whole block. In March 2019 we carried out a basic foundation survey: floor levelling, a bed-joint measurement for each building and a visual inspection of the front and rear façades.
Findings:
- Floor levelling in several apartments: largest height difference 6 cm, still acceptable (fair).
- Bed-joint measurement on the front façade of three buildings: 10 mm, 13 mm and 16 mm difference between left and right, very acceptable.
- Bed-joint measurement on the fourth building: at least 45 mm, moderate to poor; the lean is visible to the naked eye, both horizontally and vertically.
- No cracks or subsidence in the brickwork of the other three buildings; the courses run neatly level.
- Assessment: three buildings fair (foundation code 3), the fourth building moderate (foundation code 3-4).
Advice: Have settlement bolts installed on all four buildings and monitor movement over a longer period. Foundation repair on the leaning building may be needed within 10 years, and sooner if the bolts record settlement of more than 3 mm per year.
Why it matters: A measurement above ground shows that something is wrong, but not how fast it is happening. Settlement bolts answer that question, so the client can plan the repair at the right moment rather than on instinct.
Case 5: Canal house without any lean, yet no guarantee below ground, Amsterdam city centre
Situation: National monument from 1667 on a canal in the inner city, five storeys, used as an office and unoccupied. In our view the rear building was added later, probably around 1960. In January 2022 the client commissioned a basic foundation survey. The building shares a party wall with the house next door.
Findings:
- Bed-joint measurement on the front façade: 4 mm difference between left and right, practically level.
- Bed-joint measurement on the rear façade: level to within 4 mm.
- Floor levelling on the raised ground floor: about 26 mm height difference from front to back, reasonably level.
- No serious cracks or subsidence in the front or rear façade or on several floors.
- The semi-basement could not be fully inspected because the front part was used for storage.
Advice: Based on the measurements there are no signs that the foundation is not in order (overall rating: fair). Anyone who wants complete certainty needs a further foundation survey in which the timber piles and the structure above them are excavated. If the neighbouring building’s foundation is renewed, the shared party wall will be re-founded as well; if only some of the walls get a new foundation, this may cause problems in the long run (a so-called hinge building).
Why it matters: Good measurements above ground say something about tilt, not about the condition of timber piles more than 350 years old. In a building of this age it is likely that not every pile is sound; only excavation gives certainty about that.
8. Disruption, neighbours and VvE
- Disruption. An inspection pit inside the house causes a lot of disruption. A pit of 2.5 by 2.5 metres puts almost 10 cubic metres of soil and rubble inside the home. The ground floor or basement floor has to be broken open.
- From outside. With a detached or corner house the foundation can sometimes be inspected from outside, with less damage inside.
- Buying. If you are buying, you need the seller’s permission to dig. And phase 2 takes one and a half to two months, which often does not fit a purchase condition of a few weeks. Discuss this before you make an offer.
- Neighbours. With a shared party wall, repair also needs the neighbours’ consent, and they usually share the cost. If your neighbours are going to repair, have a pre-construction survey of your home done.
- VvE. In an apartment the owners’ association pays for the repair and each owner contributes in proportion.
A phase 2 investigation does not solve a structural problem. If the situation is acute, a structural engineer is needed and, if necessary, temporary props.
9. Booking
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. A report in English costs € 100 extra.
Premiumkeur does not work with estate agents, financial advisers or contractors, and does not recommend foundation repair companies. So we have no interest in the outcome. What clients say: English reviews.
Phase 2 usually follows a building survey with a foundation risk check. Our English pages Pre-Purchase Building Survey Amsterdam and House Inspection Amsterdam explain that first step.
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.
Frequently asked questions
What does a phase 2 foundation investigation cost?
At Premiumkeur from € 3,000 excluding VAT for the inspection and report. Digging the pit costs on average € 4,000 to € 8,000, and wood samples, if needed, about € 700.
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.
How long does phase 2 take?
From order to report, on average one and a half to two months.
Who digs the pit?
A specialist company. Premiumkeur can arrange it, or you choose a company yourself. The inspection in the pit is done by our own inspector.
Is phase 2 needed to split a property in Amsterdam?
In many cases, yes. The municipality asks for a phase 2 report with the splitting permit application, unless the foundation has already been renewed.
What is the difference between phase 1 and phase 2?
In phase 1 we measure above ground and the foundation is not exposed. In phase 2 an inspection pit is dug and we look at the piles themselves.
Do I get a foundation code after phase 2?
Yes. A foundation code is only given after a phase 2 investigation.
Are wood samples always taken?
No. Only if the municipality requires it or the measurements in the pit call for it. A laboratory examines the samples for bacterial decay.
Does the floor of my house have to be opened?
Usually, yes. A pit of about 2.5 by 2.5 metres is dug in the living room or basement. With a detached or corner house it can sometimes be done from outside.
Does phase 2 fit within my purchase condition?
Often not, because it takes one and a half to two months. A quick scan (phase 0) during the building inspection does fit.