Flat roof construction

I have a bay window without anything above it, so it has a flat roof proofed with lead. I wish to rip down its ceiling (again) and do a better a job of what I did previously. I will have joists in which insulation can slot, but after that what do I do. plain plaster board or vapour barrier stuff? Outside there is a funny hole in the top of the window frame/fascia that enters this roof space. Iy may have been some form of drainage from the roof at a time past (now it shovels off the end into a hopper) This lets the rain in and with the wind in the wrong direction and a heavy downpour puddles in the room! There isn't any rot in the roof structure. But this hole may give the ventilation required to prevent it. Just want to make sure I don't create a problem by blocking it up. Are these kind of roof spaces vented if so how?

TIA, Mike W

Reply to
VisionSet
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I got no response so I'll add photo documentary, always helps ;-)

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have a bay window without anything above it, so it has a flat roof proofed with lead. I wish to rip down its ceiling (again) and do a better a job of what I did previously. I will have joists in which insulation can slot, but after that what do I do. plain plaster board or vapour barrier stuff? Outside there is a funny hole in the top of the window frame/fascia that enters this roof space. Iy may have been some form of drainage from the roof at a time past (now it shovels off the end into a hopper) This lets the rain in and with the wind in the wrong direction and a heavy downpour puddles in the room! There isn't any rot in the roof structure. But this hole may give the ventilation required to prevent it. Just want to make sure I don't create a problem by blocking it up. Are these kind of roof spaces vented if so how?

Now I have removed the T&G cladding there appears indeed to be no dampness at all, but the hole as pictured is only recently blocked up and the T&G will have been more breathable than the proposed plaster. So should it be vapour barriered? As you can see from the photo, above the glass fibre insulation are ¾" boards and above that (you can just see through a knot) the lead. The hole outside does indeed enter the roof space.

Additionally I have these questions:

What thickness of plaster board should I use? The return to the main ceiling need replaceing how do I form the corner with scratch coat on the return and board on the bay celing?

TAIA, Mike W

Reply to
VisionSet

You wouldn't get enough rain coming through that hole in the window to fill a teaspoon, the water is obviously coming in somewhere else, why not take down the insulation, then get someone to stand outside with a hosepipe on spray (or wait til it rains) and then you can see where the rain is coming in.

They don't need to be vented....it wasn't vented originally (see lower down)

It was where the old lead downspout exited the roof, you can block it up.

Whichever you like.

You need a skim bead. Board the bay ceiling. Rough in the return down to the (straight, not cut) edge of the p-board, when dry, tack skim bead on (carefully) and skim the lot....although I wouldn't be in too much of a rush to do this (again :-p) until you've found out how the water is getting in.

Reply to
Phil L

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