Mold behind baseboards - experiences?

Hi, I just removed two baseboards on exterior walls for another matter. Is that mold? On one baseboard, there are black marks like fingerprints. On the second baseboard, it looks like dirt. It could also be animal droppings.

The baseboards themselves and the wall behind are not damp, I measured. Could there still have been too much moisture in the screed? I installed the floor myself in a new building, after about 15 weeks of screed installation and partial technical drying, but I did not do a moisture measurement! It was a 7cm flowing screed. The wall is a thermal pumice stone without additional insulation. Temperature inside the house is about 23 degrees everywhere with 30 percent humidity. I sealed the top of the baseboards to the wall with acrylic.

Back to the baseboard – I put it back without any treatment. Now I am wondering – if it was mold, should I remove all the baseboards? What do you think? And if so, only on exterior walls, or really all of them?

I'm attaching two photos of each baseboard.

Thanks and regards Julian

Looks rather harmless. Yes, could be damage caused by moisture release from the screed. It doesn't dry out evenly. Possibly just knock off the baseboards and reattach new ones.

Hi, thanks for your reply.

How exactly would you proceed?

Remove all moldings immediately? Only remove the exterior walls? And if removed, treat with mold remover, dry and put back on? Permanently leaving them off is not possible because of babies. That would be possible for a maximum of 24 hours..

Or do nothing based on the pictures for now, and - say - check behind other moldings in the summer?

Thanks and best regards

That looks like a rather small infestation – more like mildew in the initial stage. It probably occurred shortly after the baseboards were installed and the residual moisture escaped. How long have the baseboards been installed? The progression of the infestation requires continuous moisture ingress. I would test 2-3 rooms and preferably exterior walls, remove the baseboards there and check how it looks. If it looks similar, I wouldn’t worry further and would reinstall the baseboards after a few days. It is currently the heating season, especially the first one after the construction and completion of the house, which brings many particularities. For example, we have noticed condensation on outdoor sockets, the front door, attic stairs, windows, roller shutter cable penetration, etc. It just needs to be worked on afterwards and then observed.

The panels have been installed, I would say, since August/September, we have been inside since October and then it was also heated. So about four months, I would say.

I am currently also tending to remove the exterior wall panels completely in the coming weeks or at the end of the heating season, to clean them, let them dry, and reinstall them. Because from your answers, I gather that there is no immediate need.

Maybe I will also take a look behind an interior wall in that context! Does that sound like a reasonably sensible plan?

I would not wait with the trial removal. Do it right now and then you will see if further, urgent action is necessary.

But I think by now it has dried out and you will only find the traces from last summer.