Dampness under bay window - Victorian End of Terrace
Damp can be a major issue in the home. Find answers to questions or post your own here.

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HandSlander
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Dampness under bay window - Victorian End of Terrace

by 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

stoneyboy
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Re: Dampness under bay window - Victorian End of Terrace

by 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

HandSlander
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Re: Dampness under bay window - Victorian End of Terrace

by 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

Warbster44
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Damp under bay window? salt substance?

by Warbster44 » Fri Nov 18, 2022 7:20 pm

I've come across something quite unfamiliar to me. I am reading it could be a salt like substance as you can see from the photos. It is lilke a fluffy substance which when you wipe it, it removes from the wall. It is coming through the brick, plasterboard and painted wallpaper. I am also starting to see water droplets on the decorators caulk in the corners.

What is the substance? Would it be a case of removing plasterboard and injecting some damp proofing?
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