Any ideas where the damp is coming from?

[Mach9]

Hi All,

There is bad damp round my son's bedroom window and it has me stumped. It runs across the top and down both sides and it bad enough it gets mouldy and the paint flakes off.

There was crumbling mortar on the outside above the frame which I thought might be the cause, but filling that has not made a difference. I have also tried replacing the sealant round the outside, but again no difference.

I am thinking that it may be somehow getting into the cavity, running down onto the lintel or top of the frame and then soaking out through the plaster, but I don't know how to validate this or how to fix it. From what I can see of the roof there are not tiles loose or obvious gaps (though it is not easy to get to). The only other thing I can think of is that it might somehow be being blown in along the soffits somewhere, but not obvious where.

It's the top left window in the external picture.

Window interior 2

• Mach9
• 9 Mar 2022

Window interior 1

• Mach9
• 9 Mar 2022

Window interior 3

• Mach9
• 9 Mar 2022

Window interior 4

• Mach9
• 9 Mar 2022

View of window

• Mach9
• 9 Mar 2022

Bedroom is the top left one

Roof

• Mach9
• 9 Mar 2022

IMG_2520

• Mach9
• 9 Mar 2022

IMG_2522

• Mach9
• 9 Mar 2022

IMG_2521

• Mach9
• 9 Mar 2022

 

[blup]

Looks like there was a fillet of mortar above the window to fill a gap when it was installed and moisture got in. You have replaced it but the damp remains. Maybe need to chop out mortar, put in plastic packing strip and use sealant not mortar to bed in. Damp should dry out but maybe need to chop out and replace plaster if bad.

Blup

 

[crank39]

I'm going to stick my neck out and suggest it might be condensation clinging to cold spots caused by cold bridging and having it on 3 sides certainly points that way, another giveaway for condensation is the condensation building up on the inside face of the glass in one of your pictures, speaking from experience is your son reluctant to open his windows for ventilation at night pr during the day? There's water in his breath and at night he could breathe out half a pint just on his own, if he has a girlfriend then that could be more, also does he dry clothes on radiators

 

[RandomGrinch]

I'm only only a DIY'er, but agree completely with the above:

I'm going to stick my neck out and suggest it might be condensation clinging to cold spots caused by cold bridging

With the windows set so far forward, towards the front wall, insufficient insulation around the cavity may cause cold bridging?

...and if there was any water ingress passing across the cavity, I would expect that to show around the French doors as well.

Edit: just noticed the curtains are closed on the photos! Not atypical for a teenager! (Though that is a big assumption! ) - not conducive to letting air circulate

 

[^woody^]

That gap at the top of the frame.

 

[Mach9]

I'm going to stick my neck out and suggest it might be condensation clinging to cold spots caused by cold bridging and having it on 3 sides certainly points that way, another giveaway for condensation is the condensation building up on the inside face of the glass in one of your pictures, speaking from experience is your son reluctant to open his windows for ventilation at night pr during the day? There's water in his breath and at night he could breathe out half a pint just on his own, if he has a girlfriend then that could be more, also does he dry clothes on radiators

Thanks all for suggestions. My son is actually away at Uni at the moment, so I can't blame his breath! First stop, I will take a look at that fillet of mortar again and see if replacing that addresses it. If not something will see if I can work out about cold bringing.