Mould remedy/insulation on non cavity walls

[zippyswife]

Desperate for some advice on this.

I have 1920s house- ground floor is cavity wall and there is no mould issue. Upstairs is solid wall and we have mould in the corners of all the external walls and on the external walls. Ds bedroom has 3 external walls which is a massive problem and the mould spread really badly behind all furniture which I was completely unaware of for a while.

A builder came in and advised that he could put battens on the walls and stud walls and re plaster to effectively create a 50mm cavity to prevent the mould from “jumping” he was convinced this was the best remedy and would completely solve the problem. However he hasn’t yet given me a quote and I fear that this may not solve it.

i don’t have air vents or trickle vents. Would both these improve it enough to minimise the problem without the extreme suggestion of the builder.

Ultimately i need to get this sorted but just need to know the best way to tackle it effectively. I don’t want to throw money at something that’s not going to work.

Any advice on what I should be doing would be gratefully received!

I suspect you may have a few issues here - three external solid walls means it will be very cold, so he is suggesting a type of internal wall insulation, or would be if he was going to either use insulating boards or put flexible insulation between the wall and new boards. However, not an expert so don't know if you need to preserve a gap.

Is there any chance you may have damp? if so that would need sorting out first or mould will just carry on occuring.

Thirdly, it is likely that if the furniture is very close to the wall, there may be lack of ventilation and condensation occurring, so that moist air is condensing against the colder walls and causing the mould

internal wall insulation tends to be quite expensive as it involves moving radiators, sockets and bring window architraves forward etc. i would try and move the furniture away from the external walls a bit, clean up the mould and see if that helps a bit. However, ultimately, cold walls are going to be more prone to such condensation type mould.

The mould grows where walls have condensation settle - so on cold surfaces. Warm air holds more moisture than cold air, so when temperature falls at night the water condenses onto cold surfaces. Older houses should allow.water vapour to pass through the walls so need breathable paints, plaster, etc. It could be that the cavity wall insulation has caused some damp issue upstairs, but I dont know enough to know!

So, to fix it...
you can remove lots of the water from the air - ie a dehumidifier, and/or ventilate
Limit the moisture in the first place - eg extractor fans, dont dry clothes indoors, check youre gutters arent blocked, etc.
Make surfaces warmer. EG internal wall insulation (you might get a grant for this? Its messy and disruptive and quotes we got were expensive!). You could try "anti condensation paint". Theres a company called Lakeland Paints who do this, though they might call it "insulating paint" - I got a sample and where I painted it as a tester the wall was noticeably warmer to the touch than with regular paint. I dont think it could actually reduce heat loss through walls as its too thin a layer.

Im not sure how adding normal, uninsulated plasterboard would really help, you'd be better with internal wall insulation if youre going to that much hassle.

Mould is caused by damp. Damp in bedrooms comes from people and has to be removed by ventilation.

i would have continuous extract from any areas generating moisture - kitchen, bathrooms etc and trickle vents added if windows newish double glazed. Warm wet air can travel from ground floor. You need to slowly draw fresh air through the property. Moisture needs to go somewhere