DIY Doctor

Main navigation

Damp window revels in cavity walled cottage

Postby Wilde08 » Wed Dec 08, 2021 9:56 pm


We installed brand new double glazing in our cavity wall cottage 5 years ago, when its really cold outside only in our bedroom the window revels look half damp and black mould is starting to appear.
The window has trickle vents which I have experimented opening and closing which doesn't seem to make a difference. The windows also have a lot of condensation on when it is also a cold night/morning.
None of our other windows in the house have the same issue.

Do I need to Repoint/Mastic the window outside?
Do I need to take the windows out and see if the Window reveals are insulated/thermal bridging?

Please help Im getting it in the ear by the wife which Im sure you can all understand!

Many Thanks
Rank: Labourer
Progress to next rank:
Posts: 1
Joined: Wed Dec 08, 2021 9:38 pm


Simply Build It

Postby stoneyboy » Thu Dec 09, 2021 10:55 pm

Hi wilde08,
You have two separate issues, being a bedroom you will exude damp air while you sleep, unless you open a window humidity levels will be high by the morning causing condensation.
It is very unlikely that you have insulated cavity closers, you probably have masonry infill which causes thermal bridging. Add to this that your new windows probably have a narrow frame section than the old ones so part of the outside wall will be exposed on the inside of the frame.
You could try fitting a upvc trim (the thicker the better) around the inside of the reveal next to the frame.
Regards S
Rank: Project Manager
Posts: 5084
Joined: Wed Dec 10, 2008 6:44 pm

Display posts from previous
Sort by
Order by

  • DIY How to Project Guides
  • DIY how to tutorial projects and guides - Did you know we have a DIY Projects section? Well, if no, then we certainly do! Within this area of our site have literally hundreds of how-to guides and tutorials that cover a huge range of home improvement tasks. Each page also comes with pictures and a video to make completing those jobs even easier!

  • Related Topics