ᐅ Damp Basement Wall – How Does Water Penetrate?

Hello dear forum members,
we have purchased a house built in 1980 and noticed that when the groundwater level rises significantly, water enters at two or three spots where the basement floor and wall meet, which results in damp walls.
As far as I can tell, the basement floor and wall were poured up to a height of about 1.5m (5 feet). The masonry was applied only above that.
From the outside, it appears that there is a black waterproofing layer (as thin as paint) on the calcium silicate blocks, which I hope extends down to the foundation.
This summer, I plan to work on the waterproofing of the house walls and fully renew it.
My general question is: how can water penetrate into the interior in the area where the floor and wall (which seem to have been poured as one) meet?
I am a beginner and eager to do the work myself, so I appreciate any advice!
Best regards

It is quite common for moisture to penetrate after 40 years. The coating, whatever type it may be, also deteriorates over time. You will have to excavate around the entire building and reseal the wall from the outside. There are different systems for coatings, membranes, and similar solutions. I would recommend consulting your local building materials supplier for advice. And while everything is exposed, it would be a good idea to install a drainage pipe as well.

Additionally, it has proven effective to work on one side at a time and not to expose all directions down to the foundation simultaneously (especially not too deep). Otherwise, you might encounter problems beyond just a damp basement.

Excavate section by section and waterproof from the outside, install drainage. Possibly also use an injection system to make the walls themselves more impermeable.

rick2018 schrieb:

Possibly make the walls more impermeable using an injection system.

Injection, however, is not suitable for pressure-driven moisture but rather for rising damp! When opening the walls on one side, however, the effort to measure the drainage is higher.

Would you apply a bituminous waterproofing layer on the inside of the concrete slab? Or leave the slab untreated?
And would you additionally install a horizontal damp-proof course above ground level (cut and injection) to prevent capillary moisture from rising into the ground floor walls?

I had a project like this a while ago and wasn’t sure how to approach it... In the end, I didn’t have to make the decision.