Sounds like a condensation problem.Never easy to get rid of.Certainly treating with bleach or mould remover will give temporary solution.
But you need to get to the root cause of problem which is caused by warm moisture laden area cooling down and condensing on cold surface where air circulation is at its lowest ie in corners or/and behind large objects of furniture.
Letting more cold air into room is unlikely to help,if a bathroom is nearbye keeping door shut until steam clears could !
The most practical thing is to raise surface temp by insulating in cavity walls,if no cavity then try thermal wall paper liner.
Other things to help
Raise air temp.
Increase ventilation to that area
Reduce moisture content of air
Avoid flash heating,keep temp more constant
Steve Tuckey of Swiftsure
Hi Sue,I would suggest two courses of action:;
. Increase the ventilation in the room by means of an Expelair and or window vents
. Clean Black spots first with antifungacide then seal with oil based primer,then paint room with two coats of Emulsion either Eggshell or Diamond Matt.
look for any issues with your roof.
The issue is quite possibly damp caused by a leak, and with you saying the issues are in the corners, look firstly at the pointing to the ridge tile then assess your eaves felt.
Hope this helps.
First discover what is causing the mould. Could it be a cracked roofing tile, or maybee an area that needs pointing on the outside brick work. Is the brickwork 9" or cavity. If it turns out that these points are o k try putting in an air brick with an internal closing vent.
I agree with all the others however there is another cause if it is in the top corner of the room upstairs. This is potentially down to having too much insulation in your loft therefore not allowing the house to breath ( old houses had air bricks to combat this issue ). If you recently took part in the government incentive for loft insulation it is not unknown for companies putting too much in.
The black mould spores feeds on condensation which condenses out on a cold surface . The surface in question is probably less than 10 deg c , if you turn up the heating and increase the ventilation, a bit , it may disappear .
I have a spot in my hall , that if I turn down the rad, a black mould spot appears , turn it up, and it is gone .
A laser thermometer shows this up well , normal external walls are about 14-16 deg c , and a lot less around the window reveals .
Hope this helps
Peter ----- Beamish Const Services
As the others have stated you have a problem with condensation, which is what cause black mould. Try fitting trickle vents to windows to increase air circulation and check you've not blocked the roof vents if you've insulated the loft.
An extractor fan would be the best option, to exclude all the steam from the shower/bath. If you can't afford this option, then just make sure the window is always open when there is steam in the room.
Put a air brick in or some tile vents in or install trickle vents in windows another thing to check is that if you have loft insulation make sure there's a minimum 6 inch gap towards the gutter a lot of the time people block this up
The black is called black spot mould . It is a mould that lives on condensation , in your case , in areas where the air circulation is restricted . There are two ways to stop this , clean the area each week with anti mould solution or reduce the relative humidity in the room .
I agree bleach would remove the black. You can dilute it in a spray bottle and wipe.
The black could be due to a few things.
It could be due to lack of ventilation although it's cold now a window needs to be open a
little from time to time to air a room.
Another reason could be a blocked or damaged area of guttering and sometimes loose
Or missing pointing causes damp.
I hope it just a ventilation problem for you and you cure it with the bleach
if it is on the surface of the decorated wall rather than coming through the paint / paper then it is most likely to be condensation try improving airflow by leaving small window open and move anything away from wall that may stop air movement ie. bedside cabinet etc. Also try keeping room at constant temp