I'm after some advice on this one..

I have recently refitted my bathroom and am coming to the bit I wasn't looking forward to - The ceiling.

The house is a bungalow of conventional construction and was built in 1960, the ceiling is plasterboard and was previously tiled with polystyrene on top of (or underneath, depending how you look at it) woodchip-style ceiling paper.

I intend to fit a tongue-and-groove ceiling underneath the plasterboard by fixing battens in line with the joists and then T&G across in the usual fashion, then trim at the edges to cover the expansion gap.

My question is this - What do I need to do in terms of vapour barriers / sealing etc?

Ideally I would like to install an in-line extractor in the ceiling above the bath, which will vent out through either the soffit or roof (waiting for costings on the latter option) so I don't want to create damp problems.

if u fit as you say and varnish the tounge+ groove it will be sealed ok, and if you get extractor fitted ure sorted.