Quandary regarding bathroom ceiling vapour barrier

Hi Folks, Okays, I have done some searches, but nothing definitive has appeared, hence this post.

Our bathroom has an adjoining "cubicle" area which (I guess) was designed as a shower cabinet (all three walls of the cubicle are solid block walls; the cubicle is accessible from the bathroom proper). There used to be a shower installed in there, but to reduce the height a false pine ceiling (tongue and groove) was installed hence isolating a cuboid space of about two feet in height above the shower. This false ceiling comprised of a perimeter of two-by-two wood, a strap across the middle and the 10mm pine boards nailed up to this frame.

We are refurbishing the whole bathroom, hence my curiosity got the better of me and thus I decided to remove the false pine ceiling. The plasterboard ceiling above the (now removed) false ceiling was painted a Barbie Pink colour, but it also was significantly covered in black mould.

I plan to remove this plasterboard (taking precautions not to breathe the ensuing dust) and reinstate it. I plan to install a vapour barrier above the new plasterboard first.

When I showed a friend this present state of ceiling and explained what I planned to do, he mentioned that the addition of a vapour barrier was more likely to induce such fungal growth than if I didn't install one.

I wonder if he's right (hence this post): would it not be true that adding a vapour barrier prevents the dissemination of humid air hence the humidity is higher within the bathroom? Or is this a half-truth: in the absence of forced ventilation it is true that no vapour barrier is better than a vapour barrier?

I'm no expert at this, hence it's time to humbly engage the collective wisdom of the group.

Thanks in advance

Mungo

Reply to
Mungo Henning
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I think he is likely right.

What you need is a vapopur barrier immediately above the false ceiling, not a nice void that traps moist air above it.

OTOH if the false ceiling is staying out, then you should use a vapour barrier at that point AND a bathroom fan..

Reply to
The Natural Philosopher

I covered my enclosed shower ceiling with ply then ,then glued some upvc sheet, sealing the edges with upvc quandrant beading and silicone.,very neat and no mould

Reply to
ALex

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