Black spot on the foundation

[Eli Smith]

Hi,

This is the second time I see black spots on a foundation. Can anyone tell me if this could be mold or what can be the cause of it?

I am thinking maybe the exterior waterproof protection is deteriorated or a type of glue for the expended insulation? Simply mold?

There were no signs of any fireplace near the spots.

Bungalow
1976

Thank you

Eli

[Matt Fellman]

It sure looks like mold to me. Is that a north side or another area that would be cooler or damp? I'd likely write it up as potential mold which is beyond my scope. Further evaluation from a specialist, etc, etc.

[John Kogel]

It was black mold yesterday, April 1. ;)

Mould needs food. Concrete by itself doesn't support growth like that.
We need clear pictures.

[Raymond Wand]

Combination of air leakage at sill plate bringing in dirt and condensation forming creating staining. Top of foundation wall not insulated and coldest area is at top of foundation which is most likely above grade.

[Mark Reinmiller]

Looks a bit like sprayed on asphalt.

[Raymond Wand]

Second photo shows a lot of white staining on floor joists. Also noticed rust stains below black staining in the first photo.
As to staining being mould you would have to lift a sample and have it tested to confirm.

In my opinion its not mould.