What could cause this damp?

[Wattsicles]

Hi, does anyone have any ideas what could cause damp here in this upstairs bedroom? Roof / parapet wall issues? Condensation? Rain seeping through the walls (external wall is South West facing so receives North winds / rain)? Or something else?!

I've checked the guttering and can't find any obvious leaks anywhere. Our old single pane sash windows were replaced with new double glazing last year. I haven't found any obvious leaks in the roof and I've just had some water proofing applied to parapet walls (roofer suggested some hair line cracks were present) so I'm wondering whether this could be related although not sure that would result in the damp adjacent to the window. Has anyone else experienced similar or has any advice? I'd be really grateful! Thank you.

 

[Koolpc]

Could very well be condensation...

 

[Ivor Windybottom]

It's likely to be that wall between your roof and your neighbours. When it's windy, rain is being driven sideways off the edge of the tiles and is running down that wall.

Have a look in the loft, see if you can see water marks down it. Also next-door's side if you can arrange it.

 

[Wattsicles]

It's likely to be that wall between your roof and your neighbours. When it's windy, rain is being driven sideways off the edge of the tiles and is running down that wall.

Have a look in the loft, see if you can see water marks down it. Also next-door's side if you can arrange it.

Thanks. Do you mean the raised parapet wall on the roof? And rain is coming off of the coping stones on top and running down the parapet wall? I've just had waterproofing applied and also had the coping stones repointed so hopefully that helps. Would that theory account for the damp that's on the front facing external wall by the window though?

 

[Ivor Windybottom]

The weak point is where the tiles meet that parapet wall. However waterproof the wall and tiles, driving rain can be forced sideways off the edge of the tiles. Yes there's a flashing there but they're often inadequate.

We have a couple of places where we get water in when it rains heavily and there's a strong wind in one specific direction. It's pending a re-roof, I'll ensure some kind of modern system is used instead of the old lead flashing.

In your case, you should be able to see evidence if you look in your loft. With a good torch and mask, shove yourself into the eaves, ideally while it's raining.