What is this stuff on my painted walls and how should I treat it?

dulcificum · 18 Nov 2020 at 12:31

This is about three years growth but it must have been pretty slow because we didn't really notice it until now.

What is this? It's not damp or cold to the touch.

bloodiedathame · 18 Nov 2020 at 12:37

Mildew probs, get some H+G mould remover on it. Guessing a wardrobe was up to the wall and this was what was left behind it?

Will Gill · 18 Nov 2020 at 12:38

Mould, Zinsser will fix it

dulcificum · 18 Nov 2020 at 12:46

Thanks both. It looks kinda oily almost. But no it wasn't behind any furniture and I don't think there's that much humidity in the room.

Just found this in another room too. Also seems like mould but a different type?

alexakasloth · 18 Nov 2020 at 13:26

Outside facing walls?
Looks like mould, clean it off with bleach and water. If it's stained then zinsser as mentioned is good to stop bleed through.

dulcificum · 18 Nov 2020 at 13:44

Yeah all outside facing. Is Zinsser better than HG? HG seems to get better reviews especially for on paint. Also Cillit Bang seems good.

alexakasloth · 18 Nov 2020 at 15:20

I couldn't tell you what is better as I haven't used HG, I have used zinsser on a patch we had and it worked well.

Couldn't tell you what is causing it though (condensation? leaking gutter?), which is something I would look into to stop it appearing again.

bloodiedathame · 18 Nov 2020 at 15:48

H+G is a mould spray and Zinsser is a paint. Clean up with the spray and repaint with the Zinsser and try to get a bit more airflow in the room (eg trickle vents) or dehumidifier.

koolpc · 18 Nov 2020 at 15:52

Condensation issue. Cold, outside wall. Warm air inside condensing on cold surface.

dulcificum · 18 Nov 2020 at 15:54

bloodiedathame said:
H+G is a mould spray and Zinsser is a paint. Clean up with the spray and repaint with the Zinsser and try to get a bit more airflow in the room (eg trickle vents) or dehumidifier.

Oh I thought they were talking about Zinsser Mould Killer. We will need to use a different paint to match the rest of the room.

dulcificum · 18 Nov 2020 at 15:55

koolpc said:
Condensation issue. Cold, outside wall. Warm air inside condensing on cold surface.

To be fair, there hasn't been any noticeable condensation at all on the walls. But will look into it.

bloodiedathame · 18 Nov 2020 at 15:59

dulcificum said:
Oh I thought they were talking about Zinsser Mould Killer. We will need to use a different paint to match the rest of the room.

I wasn't aware there was one in honesty. My bad. I've used H+G a lot and it's great stuff. I assume Zinsser do anti-mould paint, I'd look into that if I were you.

dulcificum · 18 Nov 2020 at 16:09

Yeah but I can't use their paint as it won't match.

gort · 19 Nov 2020 at 05:12

dulcificum said:
Yeah but I can't use their paint as it won't match.

Look for anti-mould paint additive.

Doug2507 · 19 Nov 2020 at 05:59

The H&G stuff is ace. Used it in our bathroom and moulds never come back. Not a mark on the paint either.

Fourstar · 19 Nov 2020 at 09:32

dulcificum said:
Yeah but I can't use their paint as it won't match.

I've used Owatrol VC175 in the past. I can't comment on the effectiveness beyond saying the mould never returned where I used it. Saying that I believe mould will eventually return regardless of what you do if the conditions are damp enough.

It comes in a 50ml bottle for ~£15 which is enough for 10L of paint. It doesn't change the paint colour or finish so you can mix up smaller quantities and only use it on the affected walls.