Basement Inspection

A cellar or basement (kelder or souterrain) gives an old Amsterdam house extra space. It is also the part of the house where water gets in most often. Sometimes through the walls, sometimes through the floor, but just as often through a light well without a drain, a threshold that is too low or a sewer that backs up during a cloudburst.

On this page you can read what we find in basements, where the water usually comes from, what injecting does and doesn’t do, what to watch for when a company promises you a quick fix, and what repairs cost. Everything is based on our own reports.

Nederlandse versie: Kennisbank Kelderinspectie. Reviews from English-speaking clients: English reviews.

In brief

An old brick basement is almost never completely dry. Brick walls laid in lime mortar let moisture through. Up to a point, that comes with an old building.
First the cause, then the solution. Groundwater, rising damp, rainwater, a sewer that backs up and condensation each need a different approach.
Injecting is not a miracle cure. With small, local damp patches and little water pressure it can help. In a basement that lies below the groundwater level, it is often a stopgap.
A truly watertight basement usually means a concrete basement tank, and that is foundation work.
A basement inspection at Premiumkeur costs € 699 including VAT. You receive the report within two working days.

1. Cellars and basements in Amsterdam

In the old city, many cellars and basements are only a metre or a little more below street level. Groundwater in Amsterdam is high. The old basement walls are brick, laid in lime mortar, and the floors are often brick or a thin layer of concrete. A basement like that was never meant to be dry living space.

In newer basements, or in buildings where the foundation has been renewed, a concrete basement tank (kelderbak) has often been made: a watertight concrete tank with upstanding edges. It can stay dry, but only if the tank has been built properly and the edges are high enough. We saw problems there too: a skirting that was too low, or a new tank where the floor near the bathroom still got wet.

So if you buy a home with a basement or want to turn it into a bedroom or bathroom, you need to know beforehand what kind of basement it is and how wet it is.

2. What we find in basements

For this page we read 38 of our own reports from 2018 up to and including 2021 in which we assessed a cellar or basement: basement inspections, damp inspections, pre-purchase inspections, long-term maintenance plans and foundation investigations. 34 of them are about Amsterdam.

Rising or penetrating damp in the basement walls: in almost two in three.
A risk of water from outside through the sewer, the pump, a missing non-return valve or a light well: in more than four in ten. Some of those basements had already flooded.
Rainwater coming in through a threshold, a light well, a downpipe or the neighbours’ roof: in about a third.
A cellar or basement that is not watertight or leaks: in almost a third.
Wood rot in floor joists resting on the basement walls: in about a quarter.
Lining walls that hide the damp, so that the wall behind them can’t be assessed: in about one in five.

What stands out: the water by no means always comes through the wall. A good share of the wet basements had a problem with the rainwater drainage or the sewer. That is usually much cheaper to solve than the basement itself.

3. Where does the water come from?

In our reports we see five sources. Often two or three are at play at the same time.

Groundwater through the wall or floor. After long periods of rain the groundwater rises. In a basement that is not watertight, puddles or wet patches then appear on the floor, often along cracks.
Rising damp in the walls. Brick walls draw moisture up from the ground. You see a wet band, salt deposits and plaster coming loose at the bottom of the wall.
Rainwater from outside. A light well without a drain, a terrace that is higher than the basement, a leaking downpipe, a threshold that is too low.
The sewer. An old cast-iron sewer pipe that leaks, a pump pit that doesn’t work properly, or a sewer that backs up during a cloudburst because there is no non-return valve.
Condensation and construction moisture. Warm, humid air condenses on a cold basement floor or wall. After a renovation, thick new plaster can also release moisture for months. It looks like a leak, but it isn’t.

Only once it is clear which source it is can you say anything sensible about what will help. In one of our cases, a basement that had been measured as “wet” turned out to be dry: the moisture came from new plaster (case 1).

4. Injecting against damp and leaks in the basement

With a wet basement, the word injecting soon comes up. A product is injected into the wall or floor that is supposed to form a water-repellent layer. What do our reports say about it?

Where it can help

With a few small, local damp patches, in a shallow basement where the water pressure is low, or as an addition to other measures, we have sometimes advised injecting. Usually with the remark that there is no guarantee the problem will go away.

Where it is often a stopgap

With an old basement with brick walls and lime mortar, or a basement that floods when the groundwater is high, we wrote in several reports that injecting is money down the drain. The water then finds another way, or the wet wall doesn’t absorb the product properly. The problem seems solved for a while and then comes back.

That fits European research led by TU Delft (EMERISDA, 2013). It showed that injecting very wet walls can give very different results than drier walls, and that the usual methods against rising damp don’t always work. See the TU Delft report.

What that means for you

First have it established independently where the water is coming from.
With a quote for injecting, ask exactly what is guaranteed: watertightness, or only that the work has been carried out? For how long, and what is excluded? The Dutch consumers’ association Consumentenbond advises asking for a generous guarantee on watertightness and having an investigation done first (Vocht in huis, in Dutch, June 2026).
A basement that really has to be watertight, for example for a bedroom, usually calls for a concrete basement tank.

5. Promises in damp proofing: what to watch for

There are many good professionals working in damp proofing. There are also companies that promise a lot and guarantee little. We don’t name names, but we do give you the signs we come across in practice:

A free damp measurement or inspection by the company that also sells the solution. The cost is earned back through the work that follows. That makes the advice harder to check.
A salesperson at the door or on the phone. Don’t sign straight away. For sales at the door you usually have a 14-day cooling-off period; see your rights with doorstep selling (Rijksoverheid, in Dutch).
Boxes and devices that “drive moisture out of the wall”. In April 2026 the consumer programme Radar reported that experts from TU Delft and the University of Twente doubt whether such an electronic box works (Radar, 20 April 2026, in Dutch).
A “lifetime” or very long guarantee without clear terms. Read what is guaranteed. Often the guarantee covers the work carried out, not a dry basement.
One solution for every problem. A basement with a leaking sewer gains nothing from an injection in the wall.

Premiumkeur does not carry out repairs and does not sell damp proofing. That means we can tell you what is going on without a stake in it, even when the answer is that you can live with a bit of damp.

6. How our basement inspection works

Moisture measurements at different heights in the walls and on the floor. That shows whether the moisture comes from below, from outside or from the air.
Checking the water routes: light wells, thresholds, downpipes, the connection with the neighbouring building.
Sewer, pump pit and non-return valve: does the pump work, is there a non-return valve, where does the rainwater go?
Structure: cracks in the basement wall or floor, rusting steel beams, wood rot in the joists resting on the basement walls, and signs of subsidence.
Photos and clear advice, with what it costs now, what can wait, and what you can leave as it is.

To be fair: behind lining walls, a floating floor or new parquet we can’t look without opening something up. Then we write that in the report and, where needed, advise further investigation.

A basement inspection, including a damp investigation in the basement, costs € 699 including VAT at Premiumkeur. More about the service on the page kelderinspectie Amsterdam (in Dutch).

7. Solutions and what they cost

A few examples from our reports (amounts as they were in the report at the time, including VAT, price level 2018 to 2021):

Repairing a light well and covering it with laminated glass: about € 900.
Renewing the sewer pipes in the basement, with a non-return valve: € 1,800 to € 3,500.
Improving ventilation: € 550 to € 1,500.
Injecting walls locally: € 1,500 to € 3,500, always without a guarantee of a dry basement.
Ventilated lining walls, sometimes together with local injecting: in our reports from € 5,000 to just over € 7,000.
Taking the floor out, digging deeper and laying a new, ventilated floor: from € 25,000.
A new watertight concrete basement tank with a new foundation: in our reports € 100,000 to € 200,000, and for a large villa even around € 500,000.

For foundation repair with a basement or for adding a basement, based on our practice in Amsterdam we work with from € 3,500 per m² (price level 2025), plus finishing work. Price factors are the surface area, access, whether the neighbours take part and how deep the digging has to go. More in the foundation investigation knowledge base.

Have you had a new basement tank made, or are you buying a house with a new basement? Then ask about the guarantee on watertightness. In our reports we advise asking for at least ten years.

8. Case studies from our reports

Six cellars and basements in Amsterdam. Addresses and names have been left out.

Case 1: the basement turned out to be dry, Amsterdam-West

Situation. An office with a basement in a building from the early twentieth century, April 2018. An earlier measurement had shown damp.

Findings. The basement tank was dry and almost watertight, apart from two small spots. The measured moisture was condensation and residual moisture from several centimetres of new plaster. A few floor joists in the party wall were affected by rising damp, though, and during heavy rain water could come in through an opening in the party wall.

Advice. Don’t inject. Strengthen the joists (about € 1,500), renew the sewer pipes, fit a non-return valve and close the opening.

Why it matters. A measurement means nothing without an explanation. This could have become an expensive, unnecessary treatment.

Case 2: a concrete floor but no tank, Oud-West

Situation. An owners’ association (VvE) in a building from 1883, September 2019. Leak investigation in the basement.

Findings. During an earlier foundation renewal a concrete floor had been poured, but not a watertight tank with upstanding edges. The brick party walls soaked up moisture; there was severe rising and penetrating damp. On top of that, rainwater from a neighbouring roof without a gutter ran down between the buildings.

Advice. Have a concrete tank made after all, and arrange the rainwater drainage together with the neighbours. According to our report, damp proofing the walls would not give a lasting result here.

Why it matters. When the foundation is repaired, the basement has to be done properly in one go. Afterwards it is much more expensive.

Case 3: a small basement that is allowed to be damp, Jordaan

Situation. Pre-purchase inspection of a listed building from the early nineteenth century with a restaurant or bar on the ground floor, May 2019.

Findings. A small, damp basement with brick walls. In several places the steel was affected by rust.

Advice. Don’t have it injected: in this brick basement that would be money down the drain. Do improve the ventilation and have the steel de-rusted and treated (about € 1,500).

Why it matters. Sometimes the honest advice is: accept some damp and make sure it does no harm.

Case 4: a shallow basement where injecting can work, Amsterdam-Noord

Situation. Long-term maintenance plan (MJOP) for an owners’ association, building from 1906, February 2020.

Findings. The basement was not fully watertight: cracks in the basement floor, mould patches and a musty smell. After a long period of rain, the association reported small puddles from risen groundwater. The basement is shallow and the groundwater pressure is not high. The sewer pipes were in poor condition.

Advice. Here we considered it likely that injecting the floor would help, with advice from a specialist on a lasting solution. In addition, renew the sewer pipes soon (about € 3,500).

Why it matters. Injecting is not always wrong. It depends on the basement, the water pressure and the cause.

Case 5: flooding through the sewer and a light well, Amsterdam-West

Situation. Long-term maintenance plan for an owners’ association, building from 1923, June 2019.

Findings. The basement had flooded several times: from the old sewer and through a light well without a drain, which also had a crack in the concrete. The rising damp was caused by those leaks.

Advice. Renew the sewer pipes in the basement (about € 2,000) and repair and cover the light well (about € 900).

Why it matters. Not every wet basement leaks. Here the solution was outside the basement wall.

Case 6: a new layer of concrete that didn’t help, Amsterdam-Zuid

Situation. Pre-purchase inspection of a villa from 1912, February 2020.

Findings. The basement was not watertight at all: water on the floor, penetrating and rising damp, green deposits. A new layer of concrete had already been poured on the basement floor, probably to stop leaks, but it had not helped. The foundation at the rear had subsided.

Advice. Renew the foundation with a new concrete basement tank, estimated at about € 500,000, and replace the sewer pipes and downpipes.

Why it matters. A layer of concrete or a coating on a leaking basement usually just moves the problem.

9. What you can do as a buyer or owners’ association

Ask the seller or the owners’ association whether the basement has ever flooded, and when. Check the minutes and the long-term maintenance plan.
Ask where the pump pit is, whether there is a non-return valve and when the pump was last checked.
Have lining walls been put in? Ask why. A lining wall doesn’t solve damp, it hides it.
Is there a new basement tank? Ask for drawings and the guarantee on watertightness.
If you want to use a basement as living space, have it investigated beforehand, and only call in a damp-proofing company once the cause is clear.

Frequently asked questions

Does injecting help against a leaking basement?

Sometimes. With small, local patches and little water pressure it can help. In an old brick basement, or a basement that ends up below the groundwater, it is often a stopgap in our experience. Have the cause established first.

Can an old basement become completely dry?

An old basement with brick walls can rarely be made completely dry. A truly watertight basement usually means a concrete basement tank, and that is foundation work.

What does a watertight basement tank cost?

In our reports from 2018 to 2021, a new basement tank with a new foundation cost € 100,000 to € 200,000, and around € 500,000 for a large villa. Based on our practice in Amsterdam, we work with from € 3,500 per m² (price level 2025) for foundation repair with a basement, plus finishing work.

My basement is flooded after a cloudburst. What now?

First look at the sewer, the pump pit, the non-return valve and the light wells. In many of our reports the water came in through the drainage or from outside, not through the wall. That is usually much cheaper to solve.

Are lining walls a solution against damp?

A ventilated lining wall can make a basement usable, but it doesn't solve the damp. The wall behind it stays wet and can no longer be assessed. When buying, it is wise to ask why the wall is there.

What should I watch for with a damp-proofing company?

Ask which cause has been established and how, what exactly is guaranteed and what is excluded, and don't sign at the door straight away. A free measurement by the company that also sells the solution is harder to check.

What does a basement inspection cost?

A basement inspection or damp investigation in the basement costs € 699 including VAT at Premiumkeur. You receive the report within two working days.

Does Premiumkeur sell damp proofing?

No. Premiumkeur does not carry out repairs and does not recommend damp-proofing companies, contractors or roofers. That keeps our advice independent.

Videos and sources

On the Premiumkeur YouTube channel you can watch our inspectors at work, in cellars and basements too.

Sources: the figures and cases on this page come from 38 of Premiumkeur’s own reports (2018 up to and including 2021) in which a cellar or basement was assessed. Addresses and names have been left out; the amounts are as they were in the reports. External sources: TU Delft, research project EMERISDA (October 2013); Consumentenbond, Vocht in huis (June 2026); AVROTROS Radar (20 April 2026); Rijksoverheid, rights with doorstep selling. Reference date: October 2026.

All services and prices are on Diensten en tarieven (in Dutch).

Contact details Premiumkeur Amsterdam

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

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