DIY Doctor

Main navigation

Dampness under bay window - Victorian End of Terrace

Postby HandSlander » Tue Jan 26, 2021 1:26 pm

Background: We've lived in the Ground Floor Flat of a London Victorian End of Terrace for 4 years.

History of High Humidity: Overall, property has been good with no visible damp but seems to have persistently high humidity which I've been unable to remedy. Ventilation and Dehumidifier reduce humidity, but upon cessation it quickly climbs up much faster than manmade sources would normally allow, settles at ~70+% even in Summer. Results in high condensation on single glazed windows and mould growth in problem areas like cupboard corners.

Construction and Modifications: Walls are 16 inch thick (yes) masonry which I suspect to be double brick on the outer leaf, a cavity, and then single brick inner leaf. There is a visible slate DPC, albeit buried under pavement level at front of property and side passage. Prior owner had "damp proofing" works done by Kenwoods which included woodworm treatment, tanking, and adding 4x clay air bricks at ground down the side of the building - these were added above the DPC, and are possibly just ventilating the cavity... the main walls also seem to be pointed in a hard mixture, possibly cement but I am no masonry expert (can provide photos).

Problem: We now have internal damp appearing under front bay window, appears to be Penetrating Damp as it is halfway between skirting and window sill. Well above both internal and external ground level.

I've photographed external and internal sides of the wall, nothing obvious. The external render is typical in the area. My theory is build-up of sediment in the cavity, coupled with ground levels above the DPC, and possible accidental ventilation of the cavity via Kenwoods retro-air bricks... but keen to get a second opinion.

Pictures too big to embed - here is an imgur album instead
Rank: Apprentice
Progress to next rank:
Posts: 7
Joined: Sun Apr 26, 2020 1:53 pm


Simply Build It

Postby stoneyboy » Wed Jan 27, 2021 8:57 pm

Hi handslander
Have you checked the join between the bottom of the window and the masonry?
There needs to be a flexible seal at this point to stop water ingress.
Regards S
Rank: Project Manager
Posts: 5518
Joined: Wed Dec 10, 2008 6:44 pm

Postby HandSlander » Wed Jan 27, 2021 9:00 pm

Where exactly do you mean - on the exterior side, where the window meets the sill? No water gets there because the window is recessed into the moulding. Also, that area is well-sealed
Rank: Apprentice
Progress to next rank:
Posts: 7
Joined: Sun Apr 26, 2020 1:53 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