mould a top of wall

[lancenotalot]

I have a room to redecorate,walls are plastered and in pretty good condition.There is quite a bit of black mould at the top of the wall and ceiling edge.I have checked the roof and outside wall and can find no water getting in.The mould seems to be fairly dry,is there anything I could use on this prior to redecorating to prevent it happening again and what would be best to remove it.

 

[Robbie uk]

The best way of treating mould like this is to use a bleach solution to wash the mould off. The bleach will kill the mould spores. It can then be rinsed and painted to your liking. You do need to be mindful of how the mould appeared in the first place. If there is no obvious leak it may weyy be condensation. This usually appears when warm air touches a cold surface like an outside wall. Also lack off airflow into the room. I have been in many rooms that have have been made worse by new double glazing. Sometimes seals the room to airtight.

 

[JohnD]

it is almost certainly condensation (unless there is a leakling roof or wet parapet poblem). Steam is lighter than air so rises to the top of the room (even when it is not hot)

You can kill the mould with bleach, then clean it off, but unless you cure the condensation it will never stop coming back

//www.diynot.com/wiki/building:condensation_in_houses

 

[lancenotalot]

I think it probably is condensation,it is an outside wall and north facing so gets very cold,will look at installing some ventilation to help reduce it in future.