Leak under dormer window on new roof.

[MacLaverty]

We have just had a roof replacement and the dormer re-cladded, the dormer window itself is original and was not replaced. The roof was finished last week but we have a leak under the dormer window on the right hand side into the loft so water is somehow getting under the cladding, lead and felt. The roofer is coming back tomorrow and has stated that he will be sealing up all the trim as highlighted to hopefully stop any water getting into the trim and down into the loft if this is the culprit. I feel like this is a shortcut but he is saying the cladding is very difficult to remove to look further. The front lead work goes up about half way between the roof and the window sill, no lead window tray, and felt above this and lead soakers on both sides. The window is sealed all the way round into the cladding, including under the window sill, I did the top seal as roofers hadn't done it as I thought they had missed it so wondering if the top of the window should have been left unsealed to let any water that gets into the top trim out again or should all 4 edges be sealed?

Where else could this leak be coming from?

 

[Alastairreid]

Terrible finishing, the corner beads will trap the water running off the face of the cladding, ditto the dormer cheek. There are many ways of detailing dormer cladding to weather it properly.

 

[MacLaverty]

I'm sorry, I don't follow as new to all this. Which are the corner beads? And our dormer before has the exact same trim and had no leaks.

The roofers plan tomorrow was the seal up all the trim around the window so water can't enter the trim which sounds like a work around but would it work as then water cannot enter? Or should I ask him to remove the cladding and have a proper look?

 

[robinbanks]

Can't see any face drains on the window so I would expect that the window is base drained into the cill and then the water runs through the cill and out of drain holes in the underside of the front most part of the cill projection

I would check that they are present and clear and if you can get the glazing out (old beading isn't always amenable to this) you can check that they drain properly. It could well be that something has been sealed up that formerly was not and was letting water in the frame (not necessarily a bad or wrong thing with pvc) out. Having the glazing out, or at least the lower beading, would also let you check whether any of the test water you pour into the drain makes its way into the roof space. If you can't dry the damp patch out first then mixing some paint into your test water may help assess whether the window is the source of the leak

 

[datarebal]

Check for window tray

 

[^woody^]

Where is the center of that damp patch relative to the cill?

Also is that a hole in the membrane directly above the damp patch?

It's no good trying to seal the cladding. Cladding is a rain screen not 100% weather resistant.

 

[MacLaverty]

Can't see any face drains on the window so I would expect that the window is base drained into the cill and then the water runs through the cill and out of drain holes in the underside of the front most part of the cill projection

I would check that they are present and clear and if you can get the glazing out (old beading isn't always amenable to this) you can check that they drain properly. It could well be that something has been sealed up that formerly was not and was letting water in the frame (not necessarily a bad or wrong thing with pvc) out. Having the glazing out, or at least the lower beading, would also let you check whether any of the test water you pour into the drain makes its way into the roof space. If you can't dry the damp patch out first then mixing some paint into your test water may help assess whether the window is the source of the leak

So the bottom window opens and drainage is fine, getting the top window replaced as it is blown so when its out will check the water is draining into the cill properly.

 

[MacLaverty]

Where is the center of that damp patch relative to the cill?

Also is that a hole in the membrane directly above the damp patch?

It's no good trying to seal the cladding. Cladding is a rain screen not 100% weather resistant.

So the damp patch is at the far right side of the cill, I've highlighted it in the pictures on the first post. It's the hole under the dormer window, the membrane carries on up to the top of the cill and lead covering the top of that, then the cladding under the cill.

Our last dormer didn't have any felt under it and never leaked and now this dormer has felt under the cladding and leaks, it's ridiculous. The roofer has sealed a few loose parts of the cladding that had gaps in and will wait till next rain but if it happens again will ask him to take the cladding off and see what's happening at the bottom.

 

[^woody^]

Most likely a problem with the membrane overlap right at that corner under the cill.

Rather than mess about with sealant and what can only be a temporary fix, have that bottom board taken off (plus the two small ones above if need be) and get the membrane sorted out, and flashing/apron fitted below the cill and lapped at the window reveals.

It does not look like there is enough overhang from the window cill, so rain is always going to get under it. Really, that bottom board should not be there, and the whole bottom below the cill flashed with lead.

 

[MacLaverty]

They have been this morning and sealed round the trim and underneath the window cill but as you said, not convinced that will do much. Will check the leak again when it rains and if still there will get them to remove the bottom board and do as you say with the lead.

I know from feeling under, the bottom lead only goes half way up the cill and then membrane. Also, I know for a fact there is no membrane overlap on the bottom right as when the cladding was off there was about a 10/15cm gap between the membrane where I could see the wooden post exposed but didn't think much of it at the time so water will be getting in from somewhere and behind the bottom membrane easily.

In regards to lead around window reveal, what do you mean by this sorry?

 

[datarebal]

Definitely the bottom board needs to come off to expose the lead tray .
The most important piece of lead on a dormer window .
I doubt there is one .
Don't get confused with the apron .
An apron alone is not enough.
Also take a look at the verge , the overhang varies from some to none .
This will allow water in behind the cladding

 

[MacLaverty]

I can definitely say there isn't a lead tray but the previous dormer didn't either and had no issues. The cill is fully sealed all the way round and underneath so surely no water can leak under? And wouldn't water just get under the lead if the water is leaking down the inside of the cladding? And can you fit a lead tray to an existing window without removing it?

And agreed, I did ask them to put some silicone or something around the verge overhang but they said it wasn't needed as this was also my concern!

If it continues to leak, which I predict it will, I have enough to go off from what you and woody have said which is great!

 

[datarebal]

No tray then it's wrong

 

[MacLaverty]

No tray then it's wrong

But would a tray stop a leak coming from above it? Like in the picture, if water was coming down the right hand felt it bypasses the tray surely by getting behind it? I don't believe the leak is originating around the cill but somewhere above and tracking down behind the cladding. I think the issue is there is no felt overlap on the bottom right so any water getting in is just travelling down and getting behind the felt if that makes sense? If it continues to leak I will bring up: the lead tray, the slate overhang and the felt overlap and hope he fixes all 3 but so far he's denying the need to do any of it saying that the aim is to stop any water getting in as if you rely on the felt it would eventually rot.

 

[datarebal]

tray stop a leak coming from above it? Like

Yes that's one of the reasons it's there . The underlay should not be the relied on weathering .
Tbh , things look untidy there. I'd certainly look under the cladding