Box gutter, leaking or condensation??

[eviliangenius]

i have a small job on that is giving me a little headache now.
20m square conservatory used as kids play room.
customer has moved furniture around and notice large damp patch on wall and rotted window board and skirting. the wall in question is what used to be and outside wall but now dot and dabbed and is now internal.
got up on the roof to find years of crap in the box gutter that sits above the damp wall. i think it had been full for a while and all the leaves had composted and i removed a good 75mm on compost like soil from the length of the gutter and even, i kid you not removed a growing tree

thinking the was the caused i re-plastered and fitted new timbers.
go back to paint and customer says the underside of the plastics that cover the box gutter is dam where it meets at the mitre.
so i removed plastics around gutter and peel a little of the foam off and struggle to see anything and no sign of leaks.

i know from past experience that these 1 piece box gutters are pretty good and have never known one leak. all the lead into walls it fine and all sealed.
before i left i removed around 300mm of the foam from the gutter and just asked customer to keep a eye on it for any leaks over night. a few hours later customer calls saying that the box is soaked and dripping like crazy. in that few hours it did rain a lot but im now thinking is it heavy condensation rather than a leak that was causing the problem originally.

thanks.
ian

 

[catlad]

I have seen a few that leaked and I never stayed around long enough to find out why. My advice to you is plug the drain and fill the gutter with water and see what happens.

 

[^woody^]

You might get condensation on the underside of a box gutter but not normally further down a dry-lined wall

There would also be some different pattern staining between penetrating moisture and condensation

Is there a cavity tray in the external wall above the conservatory?

Pictures might help

 

[eviliangenius]

I never thought of doing that, I'm gonna fill it up when I pop over today and see what happens. Thanks

Below is the wall, you can just make out the box at the top of the picture.
The mitre is where it leaks from. It was a very slow leak originally until I stripped it back of its foam insulation. Now it's a lot more water but due to condensation and in thinking the original could have been Condensation because the leak was that little.
The new board at the bottom was a patch that was replaced do to very very poor pointing on the outside dwarf wall causing massive damp on the inside of it.

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