Moisture on "interior wall" in basement

[Friteradräka]

There is moisture on the walls in the basement that do not face the outside, i.e., interior walls. The moisture has reached about 40 cm up the walls, which are made of brick with lime plaster on top.
Can there be so much moisture only from the foundation slab?
The house is from the 1930s, insulated slab, naturally.

Drainage was done a long time ago. But I think that doesn’t really solve the problem with the moisture on the mentioned walls. What do you think?

 

[klaskarlsson]

Are you sure it's an isolated slab: If the house was built in the 1930s it's most likely not...
But reasonably the moisture comes from below, so if not from the foundation then maybe some leaking pipe?

 

[Friteradräka]

Are you sure it's an insulated slab: If the house was built in the 1930s, it's most likely not...
But reasonably, the moisture is coming from below, so if not from the foundation, then maybe a leaking pipe?

Oh! Yes, you are absolutely right! A letter dropped out via autocorrect, it is uninsulated. I don't think it is a pipe because it is like two separate walls that are affected. Admittedly, one of the walls is adjacent to a bathroom, and as far as we know, most of the conduits are visible and those in the slab we are quite sure go elsewhere.

 

[Friteradräka]

Additionally, there are vinyl floors on all the floors from different time periods, with and without asbestos according to sampling. We intend to remove these in due time. Could these be a contributing factor to the moisture rising into the wall? How concerned should we be, is there anything we can do?

 

[Centano]

The moisture must go somewhere and brick absorbs well.

Plastic flooring on an uninsulated slab in a basement with incoming moisture is not recommended. Tear down to the concrete and install a moisture-resistant floor, for example, tiles.

 

[P-plats]

In our house, water also came out of an interior wall in the basement, and we first brought in a plumber who thought there might be an embedded water pipe that had started leaking. After further troubleshooting, it turned out that the drainage was too high, and since the entire floor was painted with industrial epoxy, it was completely sealed. The capillary action drew water up into the walls and it found its way out where the wall paint wasn't completely tight. Our house had fared well previously because the drain under the concrete slab was so poor that it drained out the last bit until I replaced all the drain pipes, and the problem arose the following fall...

 

[Rappala]

The moisture you see may come from different reasons, and thus, there are probably various ways to solve it. I'm not an expert, but I can share with you how it looked in our basement with similar problems, moisture in the interior walls but in our case, framed walls made of wood but plastic mats on the floor.

When I dug for underfloor heating and a new sewer stack, it became possible to see where the moisture was. In the soil along the outer wall, it was bone dry, but the further towards the center of the house I got, the wetter it became. In the middle, there was even a water mirror where I had dug the deepest. In my case, the soil consisted of pure clay with good capillary properties that can absorb water effectively. So, I assume I had a well-functioning drainage around the house that lowered the water level well below the walls and floors, but in the middle of the house, the capillary forces caused the water level to rise and become visible!

We retained the functional drainage and removed all the plastic mats so that the moisture can ventilate up, and we haven't had any problems since. If the water level in the middle of the house were higher and became a problem, perhaps a sump pump pit in the middle would be a more cost-effective solution than improving the drainage!

 

[P-plats]

The moisture you see can come from various reasons, and therefore there are likely different ways to resolve it. I am not an expert, but I can share how it looked in our basement with similar problems, moisture in interior walls but in our case, raised walls made of wood but plastic mats on the floor.

When I excavated for underfloor heating and a new sewer line, it became possible to see where the moisture was. In the soil along the outer wall, it was bone dry, but the further I went towards the center of the house, it became more humid. In the center, there was even a water mirror where I had dug the deepest. In my case, the ground consisted of pure clay soil with good capillary properties that can absorb water effectively. So I assume I had a well-functioning drainage around the house that lowered the water level well below the walls and floor, but in the center of the house, the capillary forces caused the water level to rise higher and become visible!

We kept the functioning drainage and removed all the plastic mats so the moisture could be ventilated up, and we haven't had any problems since. If the water level in the center of the house were higher and a problem, then maybe a sump pump in the center would be a more cost-effective solution than improving the drainage!

We have something similar in our garage where the slab was cast directly on natural sand in the 70s, and in the summer, water sometimes bubbles up in the middle of the garage when the conditions are "just right."
For several years now, I've improved the drainage around the garage and haven't seen this phenomenon again.

 

[Friteradräka]

Thanks for the interesting answers! One thought has actually been that it might be because the plastic mats are there and that moisture travels in the walls because that's the path available. It's our first year in the house and we've seen moisture marks on the walls during the winter, but it's only now that it has actually been wet.