Mould and wallpapering

Mimi_Arc_en_ciel

Hi, 

I would like to redecorate my daughter's bedroom but I have noticed there is mould behind the wallpaper. Her room is the coldest (2 external walls) 

What's the best way to proceed? I can treat the mould but there won't be any protection for future. 

Thanks in advance 

Doozergirl

If you have the money, a layer of insulted plasterboard on each wall. 

It will make her room warmer and should solve the mould too as you will be increasing the dew point of the wall.  

The moisture is trapped behind the vinyl layer of the wallpaper.   It may not appear if you were to use a breathable matt paint instead of paper as you'd hopefully get air circulating.  No guarantee though, if the wall is cold, it's susceptible to condensation.  

If you have trickle vents on the windows, make sure they're open. 

baser999

We had a similar issue with a couple of small sections of the wall in our lounge to the extent that some plaster had actually started to crack and fall away. We had a builder in who broke it out and replastered and suggested it was down to damp permeating the old brickwork, best remedied by masonry painting the outside and treating with Thomson’s water seal. Managed to get a couple days of dry weather last week, got the job done and inside wall definitely seems a lot less damp. Reckon another week and it will take wallpaper 🤞

flashg67

The insulation backed wallpaper is a decent compromise and does work (has for me anyway). Google insulated wallpaper / lining paper. It's not the easiest stuff to use but with a bit of patience a decent finish can be achieved, but looks better byalso  laying standard lining paper over the top before painting

FreeBear

Doozergirl said:

If you have the money, a layer of insulted plasterboard on each wall. 

It will make her room warmer and should solve the mould too as you will be increasing the dew point of the wall.  

The moisture is trapped behind the vinyl layer of the wallpaper.   It may not appear if you were to use a breathable matt paint instead of paper as you'd hopefully get air circulating.  No guarantee though, if the wall is cold, it's susceptible to condensation.

A cold wall is a damp wall. It attracts condensation, which just increases the level of damp which in turns, makes the wall even colder. Having dealt with a cold, damp box room, I can thoroughly recommend insulating the walls. This can either be with insulated plasterboard, or multiple layers of Celotex/Kingspan topped of with plasterboard (look up "warm batten method").

The room I did was a nominal 2.4m by 2.4m. Fixing 75mm of insulation to the two external walls has made a huge difference, and one does not notice the loss of floor space. With a 600x600mm Type 21 radiator (2700BTU or 800W) in there, the room is nice and toasty.

Slapping a bit of thermal wallpaper on will reduce the risk of condensation slightly, but it will do little to improve the insulation levels. There is also a very good chance that any thermal wallpaper will trap moisture in the plaster and cause it to turn to mush eventually.

Insulating the walls properly will boost your EPC rating, reduce the heating bills slightly, and should improve the saleability of the house when the time comes to move.

Mutton_Geoff

Doozergirl said:

If you have the money, a layer of insulted plasterboard on each wall. 

How rude do I have to be to it when putting it up? Just a bit of minor abuse or the full half hour? 

Doozergirl

Mutton_Geoff said:

Doozergirl said:

If you have the money, a layer of insulted plasterboard on each wall. 

How rude do I have to be to it when putting it up? Just a bit of minor abuse or the full half hour? 

🤭 I'm leaving it like that 🤣

Doozergirl

baser999 said:

We had a similar issue with a couple of small sections of the wall in our lounge to the extent that some plaster had actually started to crack and fall away. We had a builder in who broke it out and replastered and suggested it was down to damp permeating the old brickwork, best remedied by masonry painting the outside and treating with Thomson’s water seal. Managed to get a couple days of dry weather last week, got the job done and inside wall definitely seems a lot less damp. Reckon another week and it will take wallpaper 🤞

I hope it works for you, but that is not a professional solution at all. ☹️

Chloe_G

FreeBear said:

Doozergirl said:

If you have the money, a layer of insulted plasterboard on each wall. 

It will make her room warmer and should solve the mould too as you will be increasing the dew point of the wall.  

The moisture is trapped behind the vinyl layer of the wallpaper.   It may not appear if you were to use a breathable matt paint instead of paper as you'd hopefully get air circulating.  No guarantee though, if the wall is cold, it's susceptible to condensation.

A cold wall is a damp wall. It attracts condensation, which just increases the level of damp which in turns, makes the wall even colder. Having dealt with a cold, damp box room, I can thoroughly recommend insulating the walls. This can either be with insulated plasterboard, or multiple layers of Celotex/Kingspan topped of with plasterboard (look up "warm batten method").

The room I did was a nominal 2.4m by 2.4m. Fixing 75mm of insulation to the two external walls has made a huge difference, and one does not notice the loss of floor space. With a 600x600mm Type 21 radiator (2700BTU or 800W) in there, the room is nice and toasty.

Slapping a bit of thermal wallpaper on will reduce the risk of condensation slightly, but it will do little to improve the insulation levels. There is also a very good chance that any thermal wallpaper will trap moisture in the plaster and cause it to turn to mush eventually.

Insulating the walls properly will boost your EPC rating, reduce the heating bills slightly, and should improve the saleability of the house when the time comes to move.

Wouldn't the insulated plasterboard also trap moisture in the wall? Or does it allow the wall to breathe through it??

Mutton_Geoff

Chloe_G said:

Wouldn't the insulated plasterboard also trap moisture in the wall? Or does it allow the wall to breathe through it??

No because, the moisture here comes from the inside of the house, people breathing, living, cooking etc. It's why we have extractor fans in kitchens, bathrooms & utility rooms, all sources of high levels of moisture. Breathing produces lots even when we lay still (see your bedroom window in the morning).

Moisture in the air condenses when the temperature reduces to the dew point (used to be known as wet bulb temperature). Then it condenses (eg on a bathroom window). If you keep the internal surface warm, eg insulated plasterboard, then the moisture in the air won't condense and problem solved.

If the outside of the wall is getting wet, that is a different problem.

https://www.youtube.com/watch?v=ZQDcitKup_4

Doozergirl

Mutton_Geoff said:

Chloe_G said:

Wouldn't the insulated plasterboard also trap moisture in the wall? Or does it allow the wall to breathe through it??

No because, the moisture here comes from the inside of the house, people breathing, living, cooking etc. It's why we have extractor fans in kitchens, bathrooms & utility rooms, all sources of high levels of moisture. Breathing produces lots even when we lay still (see your bedroom window in the morning).

Moisture in the air condenses when the temperature reduces to the dew point (used to be known as wet bulb temperature). Then it condenses (eg on a bathroom window). If you keep the internal surface warm, eg insulated plasterboard, then the moisture in the air won't condense and problem solved.

If the outside of the wall is getting wet, that is a different problem.

https://www.youtube.com/watch?v=ZQDcitKup_4

People think that they're trying to stop water getting in from outside, when houses need to breathe both ways and the most important thing is to remove the moisture from inside.  Older houses draw moisture out through the mortar!