WU concrete - compression during the construction phase

Hi,

we are currently in the process of building a house with a general contractor who is also "responsible" for the basement.
A solid house is being built, fully basemented with a [Weiße Wanne], whereby the basement, which consists of WU concrete, is completely "in the ground," i.e., not, for example, partially exposed. In the basement itself, there are waterproof light shafts in every room. The soil survey confirms no pressing groundwater.

The WU construction is/was carried out according to the contract as follows (excerpt only):
Approx. 24 cm thick reinforced concrete walls made of in-situ concrete, 30 cm thick reinforced concrete floor slab with reinforcement, PE foil as a sliding layer, perimeter insulation with 60 mm thickness, and a clean layer with 5 cm thickness. The earth-filled WU basement exterior walls received perimeter insulation, 100 mm.

Now, the site manager and we have noticed that there are damp spots on some walls. At one spot, water slightly seeped in between the floor slab and the wall, creating a small puddle on the floor. At another spot, water penetrated the wall (photos attached). Fortunately, the site manager dealt with it immediately and is following up to "make sure everything is fine."

The spots have now each been generously injected by a company that supervised the execution of the [Weiße Wanne] (one spot about a month ago, the other about 2-3 months ago) and are now apparently "sealed." At one spot, water ran out of the wall during drilling; according to the employee's statement, he apparently had to drill through the "joint sheet"/the sealing (warning, layman) to ensure that everything is sealed.
During a renewed inspection of the construction site, we have now found new damp spots and are now uncertain "whether it is usual" that in a new building with [Weiße Wanne], that several injections must be done at different spots already at the beginning. Unfortunately, the basement is already completely filled in, and a "foil" (vapor barrier?) has already been laid inside the basement. The latter is "only" glued to the wall.

We have already informed the site manager about the renewed spots.

Has anyone had similar experiences? We are very grateful for any feedback.

If it is really a [Weiße Wanne], then it must be watertight. The problems and the regrouting confirm the suspicion that something was not executed correctly.

During a renewed inspection of the construction site, we have now found new wet spots and are now uncertain "whether this is usual,"

First step: Consult your own expert Second step: Deficiency complaint with request for rectification Third step: Have the rectification checked by an expert What is currently happening is botched.

Unfortunately, the basement is already completely filled and a "foil" (vapor barrier?) has already been laid in the basement itself. The latter is "just" stuck to the wall.

That is not your problem. If something MUST be done from the outside, then the company simply has to dig everything out, remove the insulation, correct it, insulate it again, refill the earth, and finally be annoyed that they worked sloppily. Oh, the engine in new cars is leaking and oil is running out. But we can't fix it because it is already installed in the engine compartment. What would you say...

Do you generally have the support of an expert on your shopping list for your house construction? If yes, where is/was he? If not, why not? You said the company that supervised the basement construction also sealed the leaks? What kind of company setup is that? If I understood correctly, that would give me serious cause for concern. They basically benefit from every mistake they can subsequently seal. Who hired the company for the supervision and for the sealing? Let me guess – the general contractor!

Where is ?

What I learned from our basement construction:
First of all, the cast-in-place concrete construction is well suited for sealing leaks, unlike, for example, the prefabricated element construction in “WU”.

What does the soil report say? If there is no groundwater, then at least seepage or layer water; otherwise no water would come through the borehole, right? And who comes up with the idea to drill test holes into the waterstop (Pentaflex, or similar)? That is the sealing element between the floor slab and the wall. Are there photos of the floor slab before the walls were formworked?

If a cast-in-place concrete wall shows leaks, this is usually due to incorrect processing during concreting (drop height, segregation, compaction, etc.) and/or the waterstop tape was not installed according to textbook or was even damaged. The aggregate sizes of the concrete must also be taken into account. Depending on the wall thickness, the standards say what can be used at maximum. For a 24 cm wall, the maximum grain size should be 16 mm if I remember correctly.

You won’t get a miracle cure for your current problem from the forum, only advice and tips. I believe the most important one is to have an expert on your side. One that you hire.

First of all, thank you very much! So, involving a construction expert will probably be the next step for now, and additionally waiting for the response from the GU, I am curious.

We have accumulating seepage water up to 50 cm below the top edge of the finished floor according to GA. The basement was constructed as a waterproof structure against groundwater pressure.

The basement was made by the civil engineer (ordered by the GU). This was then supervised by a company that also "provides" the warranty for the white tank (for more than 5 years). The latter also carried out the grouting.

Mainly, for now, it is about knowing whether someone has had similar experiences and whether the grouting has held permanently.

Attached are a few photos.

Especially the watertight construction requires special attention/monitoring during planning and execution.

Proper grouting in a WU construction method according to the standard is one of the most reliable procedures. I myself have no experience here, but a friend reported that spots grouted 10 years ago in his 24cm wall are still dry.

However, this is no guarantee for your case. No one can look into the structure of your concrete and say whether the work steps were carried out carefully and correctly.

Your expert will, among other things, request the delivery notes for the concrete used from the civil engineer to determine at all whether an appropriate mix was used. I would assume so. However, the fact that leaks keep appearing would also make me suspicious.

After we detected leaks, we conducted a stress test and pumped groundwater from a depth of 2.4m onto the property over several days, thereby simulating extreme weather conditions. Even after observing for 2 months (while construction, of course, continued), no further damp spots appeared.

In one of the photos, I see a blue tag on the steel reinforcement inside the formwork?! These tags from the bending shop/steel mill should be removed before pouring or before installing the reinforcement. Nobody paid attention to that with us either. I then removed them all myself (climbing around on the low loader between crane lifts). Such a 12cm long plastic tag is like a highway in the wall for water. It is often downplayed because it’s always been done that way.