Damp above Bay Window

[Kimkirsty526]

We’ve got a total mystery of where water is coming in and causing damp above our bay window.

It’s a 1930’s cavity wall build with bay on ground floor and 1st floor. We’ve changed the windows, had our roof inspected 3 times, render checked and no one able to see where it’s coming from. We know it must be penetrating damp as it goes dark and blisters when it’s heavy wind driven rain, but we’re really at a loss of where it’s coming from.

Another strange thing is I can smell wet plaster in our bedroom everytime is rains, but we have no damp at all visible in that room.

Any thoughts or advice welcome as we’re really at a loss!

 

[Deluks]

What's that on the wall above the window? It looks like someone's stuck a roll of flashband on.
It may be lead, but it doesn't look a particularly neat job.

 

[Kimkirsty526]

It’s lead. I have queried this before as it doesn’t seem to be fitted into the wall like our next door neighbours (I’m no expert). But we’ve got no sign of water ingress at all from upstairs.

 

[noseall]

We’ve got a total mystery of where water is coming in and causing damp above our bay window.

It’s a 1930’s cavity wall build with bay on ground floor and 1st floor. We’ve changed the windows, had our roof inspected 3 times, render checked and no one able to see where it’s coming from. We know it must be penetrating damp as it goes dark and blisters when it’s heavy wind driven rain, but we’re really at a loss of where it’s coming from.

Another strange thing is I can smell wet plaster in our bedroom everytime is rains, but we have no damp at all visible in that room.

Any thoughts or advice welcome as we’re really at a loss!

That lead detail looks worrying.

I'd say there is a distinct lack of insulation/cold bridging above that window. Just looks like poor detailing and not up to modern standards.

 

[Kimkirsty526]

Thanks for your replies!

I’ll get someone to check that lead detail, although 3 roofers haven’t picked up on it previously.

A builder did suggest having a cavity tray fitted, but it was quite expensive and I wasn’t sure it would solve our problem.

 

[ree]

OP,
Cavity trays wont be worth it, they will do very little "to solve your problem" and to install them you would have almost re-build the Apex - forget about them.

A gutter & RWP might have helped - &, although a bit tricky, guttering & a RWP could have been installed when scaffolding was up. The RWP could have been tee'ed into the existing shared RWP.

You could make a selfie batten, & use it from the upper window to to pic the top & side flashing - and the edge of the roof at the eaves. Then post pics on here?

Has blown CWI ever been installed?

 

[RandomGrinch]

Another strange thing is I can smell wet plaster in our bedroom everytime is rains, but we have no damp at all visible in that room.

Are the damp patches in the ground floor bay, or the first floor?
This comment made me think that the problem was the downstairs bay, when many of the comments above, have assumed a roofing issue on the first floor.
I wonder if you could confirm?

 

[Kimkirsty526]

Sorry for late reply! Those patches are sitting above the ground floor bay window. There are no wet patches on the 1st floor (bedroom) bay just a horrible wet plaster smell, I suspect from the wall below. Moisture reading are below 10% in the 1st floor bay. When I take moisture readings where the damp patches are, they spike to 30-40% in both corners to the left and right of the central window pane.

it does get worse when it rains.