New apartment, mold after renovation

Good morning everyone,

well, I came across you through the kitchen and electrical forum and hope that you will support me/us with our first own place.

Since yesterday, we are tenants of a 75 sqm apartment, renovated three years ago in winter without heating (could possibly be important).

Yesterday we stripped the wallpaper in two rooms and what did we see... mold.

Office:
- Mold spots left and right next to the roller shutter box. Already quite dark.
- Bottom left in the corner of the room.

Bedroom:
On the window seals bottom left and right (the plaster between the window opening and the window frame), on the plaster. Not yet that dark.

Photos may follow later.

Well, as already mentioned, the house was renovated three or four years ago.
This happened in winter, without heating, so the moisture of course got out of hand.

In the meantime, a young couple with a child lived there... were "clean", really good people with whom we also get along...
No mold was mentioned and in my opinion the child was healthy too.
The office (then a children's room) was cluttered with furniture (only one window).
In the bedroom (only one window) there was also a wardrobe in the middle.

The landlord was very cooperative and felt bad, wanted to take care of it immediately and paint over it?
His wife mentioned that the previous tenants often only aired with the window tilted... so no "cross ventilation".
Maybe a combination of renovation and not optimal ventilation?
Or simply "botched construction" as they say... which I hardly believe regarding these two.. but you never know and it would be really annoying for them :-/

The descriptions are probably more than sparse... but if it turns out like I have experienced several times this year (you tend to see everything quite pessimistically sooner or later) then good grief.

It would be nice if someone has tips on how to find out the "severity" of the mold (knock open the wall to see if it is also black "inside"?).
Or who can help with the inspection...

Best regards and many thanks in advance,

Daenni

Hello Daenni,

first of all, regarding your question:

You don’t need to find out how deep the mold is, this is a clear matter. Mold fungi that have settled on a plastered surface are always detectable in depth as well. To ensure a truly sustainable remediation, the affected area must be completely freed from plaster and additionally about 50 cm of the unaffected wall surface. This means, if you have visible mold on the wall, e.g. behind a cupboard, which is about 20*20 cm in size, then the plaster area on a surface of about 120*120 cm must be completely removed and a new buildup done.

Simply painting over it does absolutely nothing. Also, killing the mold with a mold remover is not sufficient, since the spores are still present and can immediately break out again under suitable conditions without any waiting time.

A specialist in mold fungi in indoor spaces can assist with the assessment.

There are many things to consider during remediation, so much so that remediation on a larger area can only be carried out by a certified mold remediation specialist company.

But what is much more important than carrying out remediation is to find out the cause of the mold infestation. This may be due to thermal bridges (window reveals) or just improper placement of furniture (cupboards on exterior walls with too little distance), etc. However, these can only be found during an on-site inspection; thermography might be recommended.

I hope I was somewhat able to answer your question; if not, we can also talk on the phone.

Best regards, Andreas

Thank you very much for the response!

Well, that makes me less optimistic.

The explanation given:

Renovation at the time (the landlord's parental home where the son now also lives) in winter, moisture in the plaster, then relatively quickly tenants moved in, a fairly dense wallpaper (I found it very thick) was pasted over it, and then the rest happened. The wallpaper initially also had traces of mold that were removed... after that, there was peace for the remaining 3 years. We are now tearing off the wallpaper and finding the "old" coating..

Cost analysis for "inspection" by a very nice lady: approximately 350 euros...

Oh man...

Hello,

sorry for the late reply.

As I already wrote, in the pictures it looks like there is mold growth on a thermal bridge; to be more precise, now that it is cold outside, a thermography should be carried out.

To permanently remove the mold growth, as described above, it is necessary to remove the plaster; however, the mold will return if the thermal bridge is not eliminated.

But to provide more precise information, it is essential to conduct an on-site inspection and perform further measurements.

Please contact a specialist/expert on site; he will surely be able to help you.

Regards Andreas

Good evening,

I am new here in the forum.

Maybe a silly question to start with, but what is a thermal bridge? I can't really imagine anything sensible under that. And why does a thermal bridge cause mold growth?

Thanks for your opinions.

Hello Saladin,

A thermal bridge (often mistakenly called a cold bridge) is an area in building components where heat is transferred to the outside faster than through the other components.

This means that the interior wall surfaces at these points cool down more, causing the warm indoor air, which is saturated with moisture, to no longer absorb the moisture at this spot and instead release it onto the wall surfaces. You can most easily see this at window surfaces or in the bathroom, where the glass or the mirror fogs up.

Mold fungi primarily need moisture to develop, more than 70%, and since this moisture is present at thermal bridges, mold will inevitably form there.