House with a wet base and pumice stone, what to do?

Hello everyone, this is my first post and I am not sure if I am in the right category here. Therefore, I would like to apologize for any possible mistakes.

We would like to buy a house. The house was built about 13 years ago with 30cm pumice stone (without a basement), but obviously the exterior wall was not sufficiently protected against splash water. Meanwhile, the house wall is so wet that even the plaster inside is blooming (about 20cm above the tiles). So we assume that moisture has slowly seeped into the masonry over 13 years. As mentioned, it is now also visible inside and the indoor humidity is also high. In addition, mold is slowly developing.

Now my question. Can the long-lasting moisture cause lasting damage to the pumice stone? Or would it be sufficient to excavate the base, dry it, and then professionally renovate it? The house has a floor area of about 10X10 m. The garage is about 3X7 m. The base would have to be excavated about 1m deep around the house and garage. Does anyone have an idea what drying the base including excavation of this size would cost?

Thanks for your help. If you need more information just write.

Good morning everyone, does no one here have any idea whether the above-described could cause lasting damage to the pumice stone or what a base drying, in the worst case including chiseling off and renewing the existing base plaster, could cost?

Hello,

Now my question. Can the long-lasting moisture in the pumice stone cause lasting damage?

Yes.

Or would it be sufficient to dig out the base, dry it, and then professionally renovate it? The house has a floor area of about 10x10 m. The garage is about 3x7 m. You would have to dig out the base about 1 m deep around the house and garage. Does anyone have an idea what base drying including excavation of this size would cost?

No one can answer that seriously for you; unfortunately, neither can I.

I can only strongly advise you to commission an expert with the matter and ask him for a report. Only then will you know exactly what kind of damage it is and what costs you have to expect to "dry" the single-family house. Furthermore, the expert will look at the entire building fabric and create a value for the property in its current condition. If you do not save money in the wrong place, you can—if necessary—hold the expert liable for any false statements in his report; the ladies and gentlemen have insurance for this.

I recently "learned" that "house inspections for the purpose of house purchases" are apparently a new business field for architects/graduate engineers in general; unfortunately, they do not guarantee what they deliver because they declare the inspection as purchase advice and thereby exclude liability 100%. So in any case, look for a licensed and certified appraiser regarding the valuation of existing properties so that you do not—in the worst case—come off worse.

Best regards from the Rhineland

OK, thank you very much for the answers. They helped me a little bit. However, a much bigger gap is currently opening up with the house project. But I will create a new post for that.

Hello,

I recently bought a house and have exactly the same problem:
Bims hollow block stones as an exterior wall, house without a basement, wall especially damp in the floor area, interior plaster swollen and flaking off.

Therefore, a question to the fellow sufferer who already had to address this problem last year:
How has progress been made in this regard?

Furthermore, I have planned an external thermal insulation, but this is often advised against for a Bims wall.
Does anyone have experience with this or know how to achieve external wall waterproofing against driving rain without negatively affecting the breathability of the wall?

Best regards