ᐅ Dark spots on a lightweight concrete slab

Created on: 12 Jan 2017 18:48
1
19Chris84
Hey everyone

I was at the construction site again today. I noticed some strange dark spots on the concrete ceilings. At first, I thought it might be mold, so I tried to wipe the spots off. However, they won’t come off. Even scrubbing doesn’t help much.

Maybe someone has an idea what this could be. What’s odd is that the spots are mostly above the windows.


Yellow foam sealant along wall-floor joint, OSB substrate visible.

Basement room with moisture and mold on ceiling and brick walls

Damp wall with mold growth at floor level next to window.

Wall with moisture and mold, edge area showing insulation material on building structure


Hope you can help me with this

Best regards, Chris
H
Hisearnest
8 Jun 2022 16:57
Great, thank you very much for the quick responses. That puts my mind at ease. My carpenter suspected residues from a release agent, but those should be just as harmless, right?

Out of curiosity, why are there release agent residues on some parts but not on others?