Damp advice/black mould

(20 Posts)
zippyswife Thu 25-Nov-21 07:50:15

We moved into a 1930s detached house 2 months ago. Since then we have had a number of black mould patches appearing in the bedrooms. It seems like a pretty significant amount given the relatively short period of time.

I believe the house has cavity walls but no cavity wall insulation (not sure if this helps understand the situation?).

Any ideas on what is causing this and how I can prevent it?

When we had the survey done on the house they identified medium levels of moisture to the ground level floors although this black mould problem appears so far to be just upstairs. Some walls also become wet with moisture particularly the bedroom which has 3 outside walls.

We do need to deal with some other damp
Issues downstairs but I thought I’d start with this.

DH thinks we need the heating on high all the time to cure this. This is his answer to most problems hmm. If anyone has any other ideas I’d be really grateful!

OP’s posts: |
ChristmasScrooge Thu 25-Nov-21 07:52:28

Do you use a dehumidifier?

Nowisthemonthofmaying Thu 25-Nov-21 07:56:16

If it's on the upstairs walls then it's likely to either be condensation or coming from outside. Do you air the house out, open windows etc often? Is all the guttering clear and in good condition?

oneglassandpuzzled Thu 25-Nov-21 07:57:10

Do you opens windows every day, even in winter? Close bathroom doors? I second the dehumidifier.

Noodleted Thu 25-Nov-21 07:59:03

We had something similar in an old flat and it was due to there not being any insulation + condensation. Basically the ceiling was much colder than the room, so any moisture in the air would quickly condensate and cause mould. The way to solve it was apparently to put insulation in (which we didn't do, it was rented). We washed it off with a bleach solution every few months and tried to keep the window open a lot.

TwoLeftSocksWithHoles Thu 25-Nov-21 09:08:22

A dehumidifier may address the problem of black mould but does not resolve the underlying problem, which may be a leaking or blocked gutter.
You need to locate the source of the problem first.

JoanOgden Thu 25-Nov-21 09:10:08

Do you dry washing inside?


cantbeforeal Thu 25-Nov-21 09:19:00

The walls/ceilings in my 1930s house look exactly the same 😭 I've tried all the solutions suggested and it's improved but never completely gone away. I'm giving up and moving house (for other reasons too not just the mould lol)

MyAnacondaMight Thu 25-Nov-21 10:30:10

That looks like environmental damp - i.e. too much moisture. Basically, all the water vapour that you’re producing by breathing, showers, cooking etc. is condensing on the cold exterior walls and causing mould.

You need to get the humidity right down. Open windows often, get more powerful extraction in the kitchen and bathroom (and use it), keep lids on pans etc. You can get hygrometers cheaply, that will measure the relative humidity of the room.

Cavity wall insulation helps in some cases, but not in others. The cavity is designed so that any damp getting in there from the outer wall doesn’t make it through to the inner wall. If you bridge that gap with insulation, you risk making your inner walls damp from rain etc.

SquashMinus Thu 25-Nov-21 15:31:16

How are you running your heating? Older houses hate the heat-cool cycle that most people set theirs to, as it encourages evaporation and then condensation of water. Best bet is to set it cool and constant; I run mine at 16 degrees constantly and have found it's fixed the damp issues the house had when moving in. That and not drying washing indoors, opening the window after a shower, etc!

zippyswife Fri 26-Nov-21 12:12:48

Thanks for all the advice. And it all seems pretty consistent which is great too. So I’ve cleaned all the black mould. It was actually more prolific than I had realised. I’ve aired the room for an hour each morning and will continue. Interesting point about the heat cool cycle. I would love to set it low and maintain that. DH wants it on high- like 20 all the time so I end up turning it off a lot. So we definitely have the problem of the heat-cool cycle. Heating is something we’ve struggled to agree on for the last 15 years! But I think we need to to crack this condensation-mould problem.

OP’s posts: |
zippyswife Fri 26-Nov-21 12:15:28

This was behind a desk- it’s happened in less than 2 months. I’ve never known anything like it!

OP’s posts: |
amyboo Fri 26-Nov-21 12:38:31

Looks like condensation. We have the same problem off and on in an upstairs bedroom above the garage where the cavity walls are uninsulated. We're currently in the middle of a huge downstairs renovation which converts the garage into loving space and we're also insulating the cavity wall to try and fix the problem....

Verite1 Fri 26-Nov-21 12:50:29

@zippyswife - how did you clean the black mold. We have some on the ceiling of our bathroom and sealant due to a faulty extractor fan. I cleaned it off and replaced the fan, but it has come back. Not sure if I didn’t get rid of it all and so it has just multiplied again as pretty sure fan is working fine now.

zippyswife Fri 26-Nov-21 16:55:20

We used the collie bang black mould remover. It came off easily presumably because it was all relatively recent.
I think I may look into cavity wall insulation too. Might be the way forward and save me money in heating too over time

OP’s posts: |
Badabingbadabum Fri 26-Nov-21 17:00:48

Is it an outside wall? Condensation over two months couldn't do anything that bad. Leaky guttering? I suspect if it is, it has been leaking a while and the previous owners cleaned it up and painted over before you moved in.

zippyswife Fri 26-Nov-21 17:52:35

The previous owners hadn’t decorated in years- they’d left everything broken so I think they must just have aired it out well 🤷🏻‍♀️

OP’s posts: |
Porthia Fri 26-Nov-21 17:57:52

We had this exact problem in our old flat. It was condensation.

Basically you need to buy a dehumidifier if you can and run that in the affected rooms and always open the bathroom window and run the fan after a bath or shower (keep the bathroom door shut at all times during / after a bath or shower). Same with cooking. Use the extractor fan and open windows in the kitchen when cooking, keep the door to the rest of the house closed. The warm, moisture laden air rises and condenses on the cold outside walls

Cavity insulation etc will also help!

Bloomsburyreader Fri 26-Nov-21 21:56:57


I have one of these. It tells you the humidity and the temperature and also temperature at which the water vapour in the air will turn back to liquid water (ie condensation). If it's too humid in the rooms you can just open the window

Bloomsburyreader Fri 26-Nov-21 22:00:20


I also have one of these. It gets good reviews (on John Lewis and on other websites but out of stock most places). and I've been super happy with it

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