Light damp on wall under window

poppellerant

I am having a small issue with a small part of my bedroom wall. Just this one part of a wall seems to be having an issue with black spots reappearing constantly - usually in the autumn and winter.

The wall in question is directly under a window sill where I have heavy, nearly floor length, curtains. I have these curtains to help keep the room warm at night. The windows are all double glazed. But to touch the wall now, it feels cold, perhaps slightly even damp, but it could be the cold making me think it might feel slightly damp.

During the autumn and winter, every 3-4 weeks I spray with Dettol mould and mildew remover and get rid of the tissue I use to clean the black marks from the wall. I shouldn't have to do this, but what else can I do?

I'd really appreciate any help on this please.

suki1964

Open the window slightly

Dan-Dan

poppellerant wrote: »

I am having a small issue with a small part of my bedroom wall. Just this one part of a wall seems to be having an issue with black spots reappearing constantly - usually in the autumn and winter.

The wall in question is directly under a window sill where I have heavy, nearly floor length, curtains. I have these curtains to help keep the room warm at night. The windows are all double glazed. But to touch the wall now, it feels cold, perhaps slightly even damp, but it could be the cold making me think it might feel slightly damp.

During the autumn and winter, every 3-4 weeks I spray with Dettol mould and mildew remover and get rid of the tissue I use to clean the black marks from the wall. I shouldn't have to do this, but what else can I do?

I'd really appreciate any help on this please.

What is the condition of the outside wall in relation to the problem inside?

poppellerant

suki1964 wrote: »

Open the window slightly

I already open it for a little bit in the mornings, as well as have dehumidifier running which isn't in the bedroom because of the noise.

I feel like I'm doing everything that I can and getting nowhere.

poppellerant

Dan-Dan wrote: »

What is the condition of the outside wall in relation to the problem inside?

To be honest, I don't know - when I next clean the windows, I will take a good look. Anything I should be looking out for?

suki1964

poppellerant wrote: »

I already open it for a little bit in the mornings, as well as have dehumidifier running which isn't in the bedroom because of the noise.

I feel like I'm doing everything that I can and getting nowhere.

Buy you aren't as you say you have full length heavy curtains up which is trapping the cold air behind them. As it gets colder outside condensation is the result- hence the mould

You are better off sleeping in a cool room with warmer bedding then a warm room causing condensation

Horizon81

How old is the house? Do you open the curtains to assist in airflow when you don't need them to be closed? You've already got a dehumidifier and open the window when possible so it points more to a north facing wall or just one that doesn't get much natural heat.

poppellerant

suki1964 wrote: »

Buy you aren't as you say you have full length heavy curtains up which is trapping the cold air behind them. As it gets colder outside condensation is the result- hence the mould

You are better off sleeping in a cool room with warmer bedding then a warm room causing condensation

I have been seriously considering changing the curtains for some time - are you saying shorter curtains will help to improve the situation?

Horizon81 wrote: »

How old is the house? Do you open the curtains to assist in airflow when you don't need them to be closed? You've already got a dehumidifier and open the window when possible so it points more to a north facing wall or just one that doesn't get much natural heat.

It's a fairly old house - at a guess, it was built in around 1910s.

suki1964

Shorter curtains will help with allowing the circulation of air

Keeping the window or trickle vent open at night is also a good idea

Do check the outside wall, make sure the pointing is still in place and that any guttering is in good repair but tbh where you are getting mould is really a sign of condensation

poppellerant

suki1964 wrote: »

Shorter curtains will help with allowing the circulation of air

Keeping the window or trickle vent open at night is also a good idea

Do check the outside wall, make sure the pointing is still in place and that any guttering is in good repair but tbh where you are getting mould is really a sign of condensation

I don't have trickle vents, but shorter curtains are definitely something for me to consider.

Gouldy wrote: »

Do you have plastic guttering?

Yes the guttering is plastic.

TheCyclingProgrammer

suki1964 wrote: »

You are better off sleeping in a cool room with warmer bedding then a warm room causing condensation

No. Warm rooms do not cause condensation. Keeping the room and the fabric of the building at a warm temperature will reduce the chances of condensation. Whilst warmer air can hold more moisture, lowering the temperature of the room will lower the temperature of the external wall and increase the chances of any moisture that is in the air condensing there.

The cause of condensation in this case sounds like cold bridging, where the warm air is reaching its dew point at the cold wall surface. The most effective, but costly solution, would be to insulate the wall from the outside.

The cheapest solution would be to increase ventilation. Passive ventilation such as wall vents or trickle vents in the window might help. You could also crack the windows occasionally to allow some ventilation but don't leave them open for too long or you'll reduce the temperature of the room.

Alternatively OP, you could try painting the wall with a paint designed to inhibit the growth of mould. It won't solve the condensation problem but it should prevent mould growth. I can recommend Zinsser Perma-White - it can be tinted to any colour and you can get it from a local decorators merchant.

http://www.zinsseruk.com/product/perma-white-interior/

I used it on the ceiling of our shower room which, despite having decent ventilation (good extractor fan and trickle vents) still gets quite steamy and some condensation on the walls and ceiling. We don't get any mould on the ceiling.

Some more advice here:
http://www.homebuilding.co.uk/2012/10/17/how-to-solve-condensation/