How much moisture in a natural cellar is "normal"?

Hello everyone,

we have bought a house, built in 1920. The house is basemented under three-quarters of the floor area. Two of the exterior walls are quite damp. However, I find it quite difficult to assess whether and how much moisture in a natural cellar is "normal"?

I bought a measuring device. In some places it shows about 20%. That's probably too much, right?

The two exterior walls face the sidewalk directly, so simply digging up is not easily possible.

Regards, Alex

I bought a measuring device. In some places it shows about 20%. That's probably too much, right?

What kind of measuring device or method is that supposed to be? I can't imagine 20% moisture off the top of my head. For freshly laid screed floors, we're talking about single-digit values, ready for covering depending on the type of screed at 0.3 - 2%. But 20%???

There are different methods to measure moisture. As far as I remember, professional devices cost well into the three-digit range? Maybe you have a cheap DIY store device and have therefore fallen for a technical trick?

The moisture meter won't get you any further here:

you know: the basement is damp. How damp exactly, what role does that play for you?

Now you have to ask yourself:
1. Does the moisture in the basement have a negative effect on the living spaces above? i.e. too high uncomfortable humidity, moisture damage to the walls on the ground floor, etc.?
2. Does the moisture in the basement negatively affect the use of the basement itself? i.e. no storage possibility for cardboard boxes, food, etc.?

If you answer both questions with "no," then just leave it as it is, especially since renovation is costly. Always ventilate the basement well is the only thing you can do.

If you answer one of the questions with "yes": renovate: excavate & seal, seal the basement floor from the inside, etc. The number on the moisture meter won't answer these two questions for you either.

Yeah, how damp exactly doesn’t matter. An old vaulted cellar is always damp. Very good for wine, potatoes, apples, very bad for textiles, cardboard, and anything else that likes to be stored dry. If you can handle this limitation, the cellar is not a deal-breaker.

I also know the measuring devices the OP means, 20% is just a damp wall, not wet, but indeed damp.

Hello,

yes, that's true. It's an affordable measuring device. Unfortunately, I am not familiar with the subject at all.

I once tested a wall in the living area "measured", and the value here is close to 0.

Yes, I just can't assess how dangerous this moisture in the basement is; among other things, there are slight mildew stains on the wall. The floor is concreted and dry. The moisture decreases upwards (towards the basement ceiling).