Mold on OSB boards in the roof after screed and plastering work

Hello everyone,

I hope I posted this in the right place.

We are currently building a semi-detached house with a shed roof. Recently, the interior was plastered and last week the screed was applied. The windows are tilted open for cross-ventilation. This was instructed by the screed installer. Today I discovered stains on the OSB boards. The general contractor says it is not a problem. It will be wiped off after the drying phase. The issue of mold worries me a lot. Have you experienced this as well? Is wiping it off enough? Please share your experience.

Thanks

Best regards

Today I noticed that there is mold on the OSB boards in the upper floor under the roof

Well, I wouldn't accept that... And that is exactly the reason why OSB should only be used as a top floor ceiling with 100% sealing. If at all.

Under the panels, after the screed has dried, insulation, foil, and then everything is covered with drywall. Do you have experience with this and how can it be permanently eliminated?

I'm not a mold expert, I had something similar in the drywall in the attic at my place, for me it was manageable or superficial and only in a few spots.

I got myself a mold remover and went over it several times, let it soak in and then wiped it off, ventilating well during the process.

However, if the mold is deeper, then the only solution is to dispose of it.

Why do they do the screed and plaster before the sealing layer to the roof is in place?

Why are they sealing the ceiling without insulation, that's the question? When it comes to mold, I would be very cautious. In case of doubt, consult an expert. Please do not rely on the statements of the [GU], because they want to avoid costs. Yes, it will then be sealed with foil after insulation. No, the companies do not always work carefully here. Therefore, it can happen later, if not done properly, that moisture gets into the insulation layer, condenses, and the insulation soaks. You have to be extremely attentive here! If I am personally asked beforehand, I always recommend [Rauspund], so that moisture can escape through the joints upwards if necessary.