How does the water get into the basement?

Hello,

we started building in January 2022 with an architect who also did the planning and construction management.
My wife and I are laymen when it comes to house construction and therefore had to rely on others.
The new building has been standing since about July 17, 2023, and we moved in on July 22.

Despite repeated requests to build a white tank (the property is on a mountain or slope), this did not happen.

My parents' house is two streets away, so I was familiar with the white tank concept.

Exact words from the architect:

I have built several houses there, and it was never needed.

And even with a white tank, the current problem probably could not have been prevented.

We now increasingly have water coming into the basement through the side of the basement apartment during very heavy rain. The walls are wet (Trotec moisture meter available) and mold and such are starting to appear!

A drainage system is present on the left and right sides of the basement apartment side.
During the shell construction phase, I already had the basement full of water twice after heavy rain.
December 25, 2022, as well as January 16, 2023.

I pointed out several times back then that the drainages should be checked.
Anyone who has had to pump out a basement (partially basemented) twice knows what a huge amount of work that is and appreciates having a submersible pump from that day on.

The architect, tradesmen, etc. unfortunately cannot find the exact cause, so it is also not possible to determine which trade is responsible and has to repair it. So it means we have to pay in advance again, and in the worst case, it might affect a trade that has no money to repair it. We are three people, and the second child is on the way. If this continues, I fear that in a few months we will have to file for private insolvency and lose everything.
You take out so much money for a house build and as a thank you get a leaking basement.

The worst thing is that you can do nothing yourself and feel completely powerless, while the trades seem to be working with finger-pointing.

That’s it for the topic of new builds.

I have not been able to enjoy the house for weeks and now deeply regret having built it.

I am open to any suggestions.
A leak detection company was already on site (at our expense) and could only determine that water is coming in but not how.

In other words, the cause is still missing.

I am also at a point now where I do not exclude legal action if there is no other way. We took out an ÖRAG home builders insurance back before construction started, as well as elemental insurance because we are on a mountain/slope.

How was the basement sealed now? Maybe upload a section. What was the recommendation in the report regarding the building waterproofing? Otherwise, do you have an inspection shaft for the drainage? First, check whether there is water in the drainage.

very heavy rainwater coming through the granny flat side into the .

Have you ever walked around the house during heavy rain and checked where the water is coming from and where it flows to, where does your roof drain?
You wouldn't want your basement to be the drain for the slope.
Or is there no surface water during heavy rain?

There is currently a parallel topic about this: Maybe you will find some ideas there.

How was the basement sealed now? Maybe upload a cross-section. What was the recommendation in the report regarding the building waterproofing? Otherwise, do you have an inspection shaft for the drainage? First, check if there is water in the drainage.

As a layman, I understood it to be a black tank and not a white one?? What exactly do you mean by cross-section? I am currently out for the company and cannot upload anything. Regarding the report, don't you have to commission that yourself? We relied on the architect who has demonstrably accompanied 5 other houses during construction before us there. I have to ask about the inspection shaft for the drainage but I think yes. According to the shell construction foreman, there was no water in the drainage. The outdoor facilities are not finished yet and rain flows down from the hill onto the property, and during heavy rain the water collects up to above the edge of the granny flat. I have to see if I have a photo of that.

By "section" I mean a sectional drawing of the house where you can see the slope and the house. A detailed drawing of the basement plinth, showing the wall construction, wouldn't hurt either. Then you can see what was done and where the mistake might be.

There must be no standing water directly at the house either. The workspace of the basement should be backfilled with well-draining material so that the rainwater can be directed to the drainage.

A soil survey is practically mandatory nowadays. If only to have everything in writing about what must be considered in the foundation. The architect may have built a lot in the area, but the soil can vary in small areas.

It may also well be that he has already made the same mistake 5 times... and so far he has been lucky...