Marks On Walls

[Dee-M-See]

Had a similar problem
called in the professionals and they said the problem was condensation
advise us to make sure the room was well ventilated
and to swop the single radiator to a double
hope this helps

[ummmm]

Have you posted in the wrong place?

[Gizmonster]

Looks like this should have gone in here:

https://www.theanswerbank.co.uk/Home-and-Garden/Question1685024.html