I'm rummaging around in my basement of a house built in 1932. I've now scraped off a lot of painted trim towards the floor. It's some stupid plastic paint that mostly just falls off. Now, however, I've come to a corner where behind the paint there's a black material I haven't seen before when I've been around other walls. Black mold??!! I thought at first, of course. But I no longer think that's right.
1. It's hard but softer than concrete, can be pulverized between fingers.
2. It doesn't smell.
3. It's scattered here and there on the wall I'm on (it's an interior wall), there are smaller parts on the wall towards the outside.
4. It's thicker towards the floor and more concentrated. But there are also scattered spots higher up.
5. It's black with a slight brown tint. And can show reflective surfaces... a bit like charcoal... Yes, it somewhat resembles coal.
6. The floor is painted with the same paint (but thicker?) as that on the wall but sits firmly and is stable.
7. It can be scraped off, is quite superficial. That is, not part of the concrete.
What is it? Has anyone seen anything like it?
Grateful for help!
1. It's hard but softer than concrete, can be pulverized between fingers.
2. It doesn't smell.
3. It's scattered here and there on the wall I'm on (it's an interior wall), there are smaller parts on the wall towards the outside.
4. It's thicker towards the floor and more concentrated. But there are also scattered spots higher up.
5. It's black with a slight brown tint. And can show reflective surfaces... a bit like charcoal... Yes, it somewhat resembles coal.
6. The floor is painted with the same paint (but thicker?) as that on the wall but sits firmly and is stable.
7. It can be scraped off, is quite superficial. That is, not part of the concrete.
What is it? Has anyone seen anything like it?
Grateful for help!
Construction veteran
· 2 746 posts
They haven't sealed it with tar on the inside?
I've encountered that in some 60s houses with basements.
Doesn't have to be original, could also be some DIY'er
I've encountered that in some 60s houses with basements.
Doesn't have to be original, could also be some DIY'er
Black glue maybe?
https://www.umea.se/byggaboochmiljo...aterial/svartlim.4.4ff54ec174f999469c519.html
No, sorry, I really have no idea!
https://www.umea.se/byggaboochmiljo...aterial/svartlim.4.4ff54ec174f999469c519.html
No, sorry, I really have no idea!
Thank you for your answers. Bitumen looked somewhat similar to some images I found. But I can't see how it would be used as glue under the floor. Maybe a bit further down and covered with leveling compound at some point. I took a picture in another corner where the floor paint has cracked and there's nothing black there. Earlier, there was a theory that they might have stored coal/coke there at some point and it got pressed in(?), but that sounds a bit far-fetched.
I'm now considering just scraping it off (since it is a limited area), painting over it, and moving on with life.
I'm now considering just scraping it off (since it is a limited area), painting over it, and moving on with life.
Renovator
· Näverkajakens födelseort
· 797 posts
Looks like asphalt. Cold asphalt was used in the past as a waterproofing layer.
Renovator
· Näverkajakens födelseort
· 797 posts
No, one used to smear it outdoors. How old is the house and is it a modular house or site-built? It might be a clever home builder who has been inventive.
1932 is mentioned in the OP's first post.....
I think it might be cork insulation, quite common at that time. Placed between the cast and reinforced concrete walls and the plaster on the inside. It's important not to paint with diffusion-tight paint because then it will peel. Asphalt was always used on the outside as moisture insulation.