ᐅ Single-family house, 1 year old: Water seeping in – what could be the cause?

Good evening everyone,

About a year ago, we bought the detached house, a solid construction built in 2001.

At first, everything was perfect; we measured everything, all the walls in the basement were dry, no signs of problems. But now one issue after another is appearing.

Now I have noticed water stains on the stairs between the garage and the basement.

It’s strange that these stains were not visible last year, especially since it was wetter back then.

What could be the cause?
What can be done about it?
Could the previous owners have known about this?

Have you changed anything?

Is the drainage clogged?

hello Tom Tom

We have only added some screed at the top of the door.

Could it have pushed away some kind of membrane?
So that rainwater flows behind it, or blocks a drainage?

If something causes pressure after a year, then you won’t stand a chance.

tomtom79 schrieb:
Could it have pushed any membrane out of place?
So that rainwater can get behind it, or block a drain?

This is how it looks from the outside