We have a conservatory with a box gutter attached to an outside wall. If it rains heavily against that wall, water runs down it, and normally is deflected into the gutter by the flashing.
Now, before the conservatory was complete, in particular before the flashing was done and interior decoration, when it rained against that wall water ran down the wall and continued on down the wall past the box gutter and down the now interior (formerly exterior) wall.
This seems to imply to me that the box gutter was bolted to the wall but not sealed between it and the wall. Even after the flashing was done, there were occasions when water was clearly coming in as the plasterboard was showing signs of damp. These were times when it rained hard against that wall with a strong wind, perhaps with the wind being strong enough to prevent the box gutter from draining, and the water was overtopping the edge at the wall side.
Would those in the know expect that:
1) The face of the box gutter against the wall would have been treated with some kind of sealant before the gutter was bolted to the wall? Or is there a good reason not to do that.2) That the floor of the box gutter as designed and built would be sloped to assist drainage?
In the end the builder inserted a wooden gutter into the box gutter, with the wood tapered to generate a slope to take water away, which seems to have cured most of it. We had a bit of damp the other day, but it's been a couple of years since I last saw that. The box gutter may have gathered leaves etc since then, trouble is it's very difficult to access.