So we've been in this house just about a year now. In a small portion of the unfinished basement downstairs there's what appeared to be some kind of oil or possibly blak sludge from who knows what. I didn't think much of it and cleaned it up sometime in the spring. Well it's just now starting to get really cold down here in Utah and out of nowhere I see this spot of black oil or sludge in the same exact spot! Now I was texturing drywall down there tonight so I don't know if it changed the consistency so ill check tomorrow morning. I took my drywall knife and scraped the excess black stuff off. But anyways what is this stuff? It's only in this one spot and no where else. It hasn't rained yet just starting to cool down.... It is supposed to snow this weekend. Any ideas what this is and how I get rid of it?

In the pictures it looks damp but it really isn't. I don't know of the drywall spray texture made it dry up at all, but that's what I'll check in the morning. Until then.... What do you think?

 

Welcome to the forums! It appears, whatever it is, emanated from within the wall cavity, as you can see from the "run" characteristic from the wall to the blob. If you clean it, does it reappear? In order to really find out what it is, you may have to do some exploratory surgery on that wall.

 

I doubt the drywall texture will make it disappear. It will likely need a coat of a pigmented shellac primer like Zinnser's BIN to seal it. It's possible a coat or two of oil base primer would also work..... BUT I agree with Larry that you should open it up to try and find the cause. A drywall repair in the corner is one of the easier ceiling repairs to make.

 

Ooh, I thought it was a floor............

 

Clarification, that is the concrete floor slab in the basement. Also, I just finished putting the wall UP!!!I didn't notice there being any problem when I was putting it up. Like I said I noticed it when we first moved it so I'm thinking it might be seeping slowly through in the colder weather? I just checked again this morning and it looks the same. I've tried googling it, but all I can come up with it black mold. Which ... I'm really hoping it isnt. What might be coming up through the floor?

 

Also meant to mention, I thought the same as you guys that it was coming from behind my brand new wall... I got down on my belly, looked under and felt underneath it all. It felt like regular dusty concrete, completely different than what the black spot felt like.

I still dont understand what this could be or how it just randomly popped up in the last week.

 

I go to the eye doctor on the 21st, can't believe I mistook a floor for a ceiling

 

It's not something dripping from the ceiling, is it?

 

In that corner of the house, is there a sewer pipe exiting or other plumbing? The black sludge is what you often find inside those nasty pipes. Not what you want to find, but something to rule out.

If it is coming up through the floor, some of Larry's "exploratory surgery" may still be necessary. Hopefully it is just something surface or left behind during the slab pour. Your texture work would have increased the humidity level and perhaps it is just a surface mold which should be easy to clean up.

Bud

 

My suggestion - clean it up, really spiffy clean and then tape down a piece of clear plastic over the area. That might tell you if it's dripping from above, seeping from under the new wall or perking up through the slab.

 

Are your drain pipes PVC or ABS? ABS drain pipes are black in color and the glue that they use to connect them is black. Could it be a plumbers spill from when the house was being build? It's fairly messy stuff compared to PVC glue. Black roofing tar is another possiblity.

Is it water based or solvent based? Do you need to clean it up with paint thinner, or just a wet rag?

 

Then there's always the option of it being black crude oil, seeping up through the floor, artesian-style. You are now a millionaire! Congratulations!

 

Alright, so we have been gone this weekend, we left for Denver Friday right after work. Friday morning, thinking it was maybe black mold (?) i used a heavy handed pouring of straight bleach right on the spot. All of this weekend it snowed, about 2.5 days straight, out here in Salt Lake City. With all that moisture I was assuming that the spot would have gotten larger, but as of this morning in doesn't look to have gotten any bigger, or change in any way.

So this morning I went ahead and poured even more bleach on it, and will report back later.

But as for questions, it is not seeping through the wall, if anything it MAY be coming through the seperation between the wall and the floor.

It is not coming from above from the ceiling. But in all honesty I think it may be seeping through the crack, as far as what it is I have no idea.

I am farely certain that it has nothing to do with moisture since we got over 8 inches of snow and the spot has not yet grown. I'm hoping that it may just be a stain from when i previously noticed it last year. And am hopeful that I can figure this out before I go to tile this floor.

 

Even if I tile over this, you don't think it will cause the tile to heave will it?

 

I'd want to know the cause of the stain/sludge and be certain it won't come back before you cover it up.

 

If yo bleached the spot and it is mold, the mold will also change color and lighten substantially. It also will turn a lighter color right away not over the course of half a day. If nothing happened, it is not mold. Try a little nail polish remover or paint thinner (mineral spirits). If that softens it then I think you just have a little tar that someone dropped in the past. It certainly looks like the drag marks on the floor going toward the wall is where someone was scraping with a putty knife.