How can I seal wooden cladding on bathroom ceiling?

[Gary111]

Hi, I have wooden cladding above a shower and all over the bathroom ceiling.
A couple of pieces of wood are slightly bowed and gappy and I am concerned that water vapour will cause damp in the loft.

Any ideas what I should do with this stuff please?

 

[foxhole]

How’s water vapour going to pass thru timber and plasterboard?

 

[Gary111]

I don't know that there's plasterboard above, if there is there are gaps in it where the cables for the downlighters are.

 

[Why Not Indeed]

Doesn't seem like a great choice of material for a ceiling above a shower.
If it were me, I would be replacing it with plastic.

 

[justigator]

Why not fill all gaps with a paintable sealant and paint over?