30-year-old basement is damp. Seal it? If yes, how?

  • Erstellt am 2024-01-13 21:38:08

Narma89

2024-01-13 21:38:08
  • #1
Hello everyone,

we are about to buy a house built in 1991, which we have also been living in for almost two years, so we basically know the quirks and defects. Nevertheless, a building surveyor was here yesterday and did not find any further defects.

Besides the poor insulation of the top floor ceiling, the biggest problem is the damp basement. We have efflorescence on several walls. In the first summer, quite a bit of wood that I had stored in the basement also got moldy, but that was most likely because I had the basement windows open all summer. By now, I know that was not very clever.

The building surveyor mentioned two options: either dig everything out and seal from the outside or use a resin injection method from the inside. I would really only be reluctant to dig it out, because then both terraces would also have to go, as would the landscaping. For the resin injection, I have an offer from acquaintances from 2021, at that time 480€/m² was estimated. For the size of the basement, that would be a mere 50,000€ without considering inflation, so it is probably more like 60,000€.

Now the question arises for me, how urgent is the problem? How damaging is it to the building structure? In my research, I found the recommendation multiple times to seal with a horizontal barrier and then with a vertical barrier from the inside. This would make the basement itself dry, but the masonry would still be wet/damp. Is that even sensible?

Would a sensible ventilation for the basement perhaps already provide relief? The basement is only to be used as storage space and workshop, where I build something every few weeks. So it doesn’t actually need to be as dry as living spaces, but I have also read that the moisture can eventually rise into the ground floor.

Also, the interior walls are most affected, which I cannot explain. Pictures 1 and 4 are exterior walls, pictures 2 and 3 are interior walls.

Thank you very much in advance for your help!
 

HausKaufBayern

2024-01-16 12:56:54
  • #2
I'll follow along. On a wall in the basement that faces the ground, we also have some efflorescence. I would first try heating and a dehumidifier. €60000 for such a measure (Harzinjektion)? That's insane.
 

ismon_rlp

2024-01-16 13:49:58
  • #3
If the water or moisture comes from outside, heating and dehumidifying may even increase the efflorescence. Efflorescence consists of salts and minerals dissolved from the stone by water, which remain when the water evaporates. When more water evaporates, more salts also remain.
 

ypg

2024-01-16 13:59:16
  • #4
I, as a layperson, have learned: always fight the cause. Why does water penetrate from outside? Which plants are therefore how close to the house? I would take a look to see if there is a connection. Because even in 1991 there were already external sealing slurries... somewhere you have leaks for some reason...
 

jens.knoedel

2024-01-16 14:08:53
  • #5

How damp is the basement actually?

I would always tackle the cause. And that could lie in the missing/defective external waterproofing. So dig out and seal. On that occasion, the basement could also be insulated from the outside.
These are indeed tasks where you can put in a lot of your own work (if you want) and that can also be done progressively.
 

Philfuel

2024-01-16 17:21:44
  • #6
I would leave the basement as it is, ventilate properly, and live with the moisture. €60,000 for a basement upgrade? Never! Think of all the things you could do with that money…
 

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