ᐅ House with damp foundation and pumice stone construction, what to do?

Hello everyone, this is my first post and I’m not sure if I’m in the right category. Please excuse any possible mistakes.

We would like to buy a house. The house was built about 13 years ago with 30cm (12 inches) of pumice block walls (no basement), but apparently the exterior wall was not adequately protected against splash water. Over time, the wall has become so damp that even the interior plaster is starting to deteriorate (about 20cm (8 inches) above the tiles). We assume that moisture has been slowly penetrating the masonry for over 13 years. As mentioned, it is now visible inside, and the indoor humidity is also high. Additionally, mold is gradually developing.

Now my question: Can prolonged moisture exposure cause permanent damage to the pumice blocks? Or would it be sufficient to excavate the base, dry it out, and then have it professionally repaired? The house has a floor area of about 10 by 10 meters (33 by 33 feet). The garage is approximately 3 by 7 meters (10 by 23 feet). Excavation would need to be about 1 meter (3 feet) deep around both the house and the garage. Does anyone have an idea of the cost for drying out the base including excavation at this scale?

Thank you for your help. If you need more information, just ask.

Good morning everyone, does anyone here have any idea whether the above-mentioned could cause lasting damage to the pumice stone, or what basement waterproofing, in the worst case including chipping off and renewing the existing base plaster, might cost?

Hello,

viedy schrieb:

Now my question. Can prolonged moisture exposure cause lasting damage to the pumice stone?

Yes.

viedy schrieb:

Or would it be sufficient to excavate the base, dry it, and then professionally repair it? The house has a floor area of about 10x10 m (33x33 ft). The garage is approximately 3x7 m (10x23 ft). The base would need to be excavated about 1 m (3 ft) deep all around the house and garage. Does anyone have an idea what drying the base including excavation of this size might cost?

No one can give you a reliable answer; unfortunately, I cannot either.

I can only strongly recommend hiring an expert to assess the situation and prepare a detailed report. Only then will you know exactly what damage is involved and what costs to expect in order to make the house moisture-free. Additionally, the expert will inspect the entire building structure and provide a valuation of the property as-is. If you do not cut corners at the wrong point, you can—if necessary—hold the expert liable for any incorrect statements in their report; they carry professional liability insurance for this.

I recently learned that "house inspections for purchasing purposes" have apparently become a new business area for architects and engineers in general; unfortunately, they do not take liability for their assessments because they classify these inspections as advising on purchases, which fully excludes liability. So, in any case, look for a licensed and certified appraiser experienced in evaluating existing properties to avoid ending up at a disadvantage in the worst-case scenario.

Best regards, Bauexperte

OK, thank you very much for the responses. They helped me a bit. However, a much bigger issue has come up with the house project. I will create a new post for that.

Hello,

I recently bought a house and am facing exactly the same problem: pumice hollow blocks as the exterior wall, no basement, wall especially damp near the ground, interior plaster swollen and flaking.

Therefore, a question for the fellow sufferer who had to deal with this issue last year: how did you proceed with it?

Furthermore, I have planned external thermal insulation, but it is often advised against for a pumice wall. Does anyone have experience with this, or how can you achieve external waterproofing against driving rain without negatively affecting the wall’s breathability?

Best regards