Leak or condensation

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1 Jul 2018
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Hi
Last summer we had a single storey extension with a vaulted roof built. The extension is divided into 2 rooms with a Velux in both.

During the snow before Christmas when we had the snow, we noticed a wet patch to the right of both Velux windows, strangely in almost identical places in both rooms.
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The builder said it was due to the snow and has put some leading on the tiles around the widows.

It dried up once the snow melted and all was good until this last week.
The wet patches have came back this week but they seem to come and go. They are normally there in the evening and gone by the morning. I'm starting to think is this due to the extra heat in the room in the evenings.

Has anyone got any ideas of what could be causing it and how we can stop it?

They are not the best but I will add some more photos I took of the roof during the build.
Thanks

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Fix some plastic over.
If water is under it's a leak.
If water is on the plastic surface its condensation
 
Looks like it's coincidental with the joint between the plasterboards.. Water dripping onto the back of a plasterboard tends to show through at the edges first
 
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This morning for the first time it has appeared on the other side of the window.

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My thinking is it's condensating in the roof space and dripping then running along the insulation until it finds a way out, which as you say @robinbanks is the edge of the plasterboard.
Also with it being north facing, there is frost on the tiles almost all winter which I guess doesn't help.

If this is the case I have no idea how to stop it, it does have a breathable membrane in place.
The builder reckons there must be a cracked tile but I have looked and can't see one.

Any ideas of what to do next will be greatly appreciated.
Thanks
 
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Can you take a ridge tile off and poke a drain camera down between the membrane and the insulation/above the membrane and see if you're getting any condensation forming on the underside of the tiles and or the membrane?

Was a VCL installed on the room side, behind the plasterboards(perhaps the insulation boards were foil taped together where the met the studs - if you looked up did the whole ceiling look silver with no wood coloured bits on show? Like this bit here:

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What is the function of the room below this rooof?
 
As well as the fact that the skylights are miles to small he has not laid the tiles correctly, they should be laid broken bonded.
 
He should have foil taped the joints on the insulation boards or installed a vapour barrier..I would say it's condensation.
 
Was a VCL installed on the room side, behind the plasterboards(perhaps the insulation boards were foil taped together where the met the studs - if you looked up did the whole ceiling look silver with no wood coloured bits on show?
I'm pretty sure you could still see the timber, I'm not sure what that single piece of silver tape was for.

What is the function of the room below this rooof?
The room below this is a seating area that's incorporated into the kitchen area.

You will continue getting this problem because he hasn't installed a vapour barrier.

That is exactly what I feared, that he had missed something like this, I guess there is no way of fitting it now or rectifying it without ripping the ceiling down?

As well as the fact that the skylights are miles to small he has not laid the tiles correctly, they should be laid broken bonded.

We actually had lots of arguments around the windows, we wanted lots more glass. Originally it was planned to have 2 larger Velux in the kitchen side and one in the Utility, we ended up with 1 small one in both as apparently the building inspector said there was to much glass per square meter of the extension. Never mind the bi-folds that were originally planned.
Sorry regarding the tiles I don't know what that means, are they rectifiable?


The builder did come out yesterday and has booked for the building inspector (one of his mates) to come and have a look tomorrow, so I will also let you know what he says
 
The tiles are supposed to be laid broken bond..like bricks.
Would need stripped to rectify.


Oh right I see, I'm guessing it is more likely to leak how it currently is?

Should this sort of stuff have been picked up by the building inspector?
 
He should have picked up the lack of vapour barrier as well as the roof.

That's what I'm worried about, if he didn't pick both errors up then, is he likely to pick it up tomorrow

Starting to really worry we will be left to rectify it all on our own back which we can't currently afford.
 
Show the BCO the pics you have before the plasterboard went on! The insulation boards should be foil taped and the roof tiles half bonded as per manufacturer's installation instructions.
The BCO has to apply the building regs as they are written regardless if he is friends with the builder.
 
Show the BCO the pics you have before the plasterboard went on! The insulation boards should be foil taped and the roof tiles half bonded as per manufacturer's installation instructions.
The BCO has to apply the building regs as they are written regardless if he is friends with the builder.
Unfortunately we have personally had nothing to do with the BCO, all correspondence with him has been through the builder and while we were at work, including his coming visit tomorrow.

So I am not sure where we stand or even who our BCO is.

I will try and get out of work tomorrow morning but doubt I will be able to
 

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