Single-family house (built in 2001) with previous moisture damage

Hello dear forum,

while searching for information and tips on the topic of building, I came across this site. I am currently considering purchasing and completing an “unfinished” single-family house.

There is a property in my family that was built about 18 years ago (approximately 80% completed) and has never been fully finished since due to various (family) reasons. It is a completed shell construction (Liopor / aerated concrete blocks, no basement), where the basic interior work (interior walls smoothed, screed floor, windows, oil heating, radiators, electrical / water pipes, sanitary rough installations) had already been started and mostly completed back then.

At that stage, among other things, moisture damage was detected (parts of the ground floor floor wet, walls visibly damp, plaster peeling off). Water was able to penetrate from the outside due to lack of or insufficient waterproofing and led to strong moisture in parts of the screed and adjacent walls. As a result, the screed was removed in the affected rooms (puddling under the screed clearly visible). A building expert then determined that the plastic foil had only been loosely installed, allowing moisture to penetrate into the plaster and masonry via the wall areas. It was also noted that the moisture barriers did not comply with DIN 18195 ff and that without excavation / exposure of the vertical surfaces, it could not be determined whether the drainage was correctly arranged or whether the front surfaces of the foundations and floor slab were properly protected against penetrating moisture. I don’t know exactly what measures were taken back then—only that the floor was waterproofed again and the screed was poured again. In addition, the damp plaster on the interior walls was removed. I am not aware of any rework on the moisture barriers or excavation work on the façade. Shortly afterward (possibly also almost simultaneously), the partially finished balcony was additionally waterproofed. It turned out that moisture could penetrate due to faulty waterproofing between the balcony slab and façade. I cannot say whether this defect (partly) also caused or worsened the first damage.

Since these measures, no further moisture has been detected—although this observation is limited to sporadic monthly visual inspections during maintenance visits.

My question now specifically relates to these former moisture damages. Can it be assumed—if for 18 years now there have been no signs of moisture (penetration)—that the damage was actually completely repaired back then? Or is it possible that moisture has continued to enter UNNOTICED all these years? But where would this moisture be then? The house is practically never ventilated through the windows because it is unoccupied, floors and walls are (at least apparently) dry, plaster no longer peels off, and no mold growth or musty odor has appeared.

I know that an assessment cannot really be made from a distance, but I would still be grateful for an initial evaluation—it would ease my worries somewhat and strengthen me in my decision.

Looking forward to your feedback!
Regards, Steff

Bring in a building surveyor/expert who measures the moisture and can also assess whether everything is okay so far. Here in the forum you will get a hundred opinions and none will help you because no one knows the property.

Stick fireproof paper to the walls inside. Call the fire department and for a crate of beer, they should attack the hut with everything they have. If the paper stays dry after 24 hours, everything is fine.

No guarantee.

Thank you for the quick feedback!

As soon as the project becomes more concrete, I would actually involve a building surveyor and also carry out measurements or have a partial removal of the screed done on a random basis.
I had just hoped that someone could give me a rough estimate based on experience.
Naively, I would assume that if water had regularly penetrated over more than 18 years or was still penetrating, it would have to be clearly visible even without moisture measurements – as was already the case back then.

:
I had actually already thought of blotting paper. However, the idea of the fire brigade hadn’t occurred to me yet. With really heavy rain, something should be detectable after all...

Once again, I do actually want to ensure later on through measurements / expert assessment that the house is really watertight. At the moment, I am only interested in an orienting assessment of the likelihood of whether the damage might still be present.

The house was not inhabited or heated during that time? Then I would urgently have all existing pipes pressure-tested. An unused building is always risky. Pipes burst or, or.

If the house now appears to be dry and also smells like that, there should be nothing serious. If water had been leaking in somewhere for 18 years, it would have left traces. The pipes were always empty, so there should be no frost damage either. Nevertheless, something like that is always a big risk; not without reason are such shell ruins practically unsellable.

P.S. the tip about the fire department is at most a joke, NO house stays dry in that case, promise.