what is that

9 years ago

Hi There,
Doing renovation I decided to replace insulation on outside walls and noticed strange holes with black substance popping up in few places without any particular order.. That substance looks like black ash and become black dust when touched. Strange thing is that it's kind of expanded inside the fall and chip concrete plaster out of the wall. In some places it show the sigh of water leaking, I guess when water made it's way between brick and concrete blocks. By the way the wall is made from one layer of brick than concrete block and a thin layer of concrete plaster inside. The house was build in 1970.. not that old.
I'm puzzled what it is. Is it mold? Why it is concentrated in those places and coming from inside the wall? Any idea what it could be? Is there any danger in it?

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Comments (5)

klem1
9 years ago
Not that the picture is much help,my guess is a type of mushroom,aka toad stool. Wear a resprerator while removing them.
kisa401
Original Author
9 years ago
Doesn't look like mushroom. May be it was before but died long time ago. It is completely dry and all but dust when I scratch it. Here is close up picture with concrete popping up.
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sombreuil_mongrel
9 years ago
Could be efflorescence plus rust. Steel expands as it turns to rust, so old embedded masonry nails could be causing the concrete to spall as these pins corrode in the moist concrete, and the efflorescence is just another effect from damp masonry. The moisture in the wall coming in from outside is evaporating into the cellar, and as it evaporates the minerals dissolved out of the wall are being deposited as crystals, like when salt water evaporates leaving salt, or hard water evaporates leaving lime.
Casey
SparklingWater
9 years ago
I think Casey is spot on. One thought is to remove the plaster-which was on occasion used as an insulator, but perhaps not a good choice in this location due to wetness.

Once you get to concrete you can better assess wetness (look at bottom concrete in particular) near ground and for what Casey said.

Doing the same in our abode. :)
kisa401
Original Author
9 years ago
Casey's theory sounds appealing. But shouldn't the rust look rusty (brown) instead of pure black?
Btw. There is no moisture. All desert dry. First floor, not a basement.
I'm going to test for mold just in case . HD has prolab mold testing kit.
If it is not mold than I have no concern and will address only those with licking signs.