Vapour barrier for bathroom ceiling?

[renovo]

Hello everyone,

I am currently renovating my bathroom.

My house is a standard Victorian house in the UK.

I have stripped the bathroom back to brick and insulated the cieling with rockwall. Walls will be plasterboarded and tiled and floor tiled also. Cement board used for the bath/shower area.

Above the cieling I have boarded the floor. with 18mm chipboard. There is a air vent installed within the roof.

I had some vapour barrier left over from my garden office build and figured I may as well use it on the cieling. The idea is to then board the cieling with moisture plasterboard and paint with a suitable paint.

Have seen mixed opinions online and from friends on whether or not this is a good idea. On one side I could brock moisture from getting in the cieling but on another side if it does get in then the barrier may trap it causing the timbers to rot.

Willing to keep it on or rip it off depending on the feedback. For the time being it's keeping that nasty rockwall contained.

Would love to hear some feedback on this.

Many thanks

 

[motorbiking]

Zero benefit behind the plasterboard, particularly since it will be covered with layers of loft roll. Personally, since its back to brick, I'd have added some PIR boards (40-50mm) on the external wall and used a tile backer board with foam core rather than aquaboard.

 

[oldbutnotdead]

As above you would have been wise to get some insulation on the walls (yes space can be an issue in bathrooms) but you are where you are.
Yes stick the vcl up, it'll keep all that waterladen air out of the roof space (I suspect the moistureproof board is less porous than standard but never checked)

 

[renovo]

Many thanks for your replies.

The VCL is a strange thing as for garden rooms it is always recommended but it seems never for a bathroom which will have significantly more moisture.

To confirm the setup is on top of the ceiling joists is chipboard 18mm. I have insulated the joists with rockwall. Then there is the VCL as seen in the photos. Final will be moisture plasterboard. I won't be putting loft roll above the cieling. I boarded it to use it for storage. Surely some moisture will make it past the plastboard making the VCL have some benefit?

Completely agree about the PIR plasterboard, that would have been wise but I missed that.

Good news is the cavity is insulated (old feather insulation) so it's not a completely uninsulated wall but the PIR is a missing trick for sure. On the external wall with the window I was able to insulate the cavity well with modern cavity insulation as below the window originally was a thin wood panel. So I insulated pushing it as far in as possible then blocked up properly.

 

[renovo]

Attached is the loft space above the room which I have boarded for storage and the absolute mess below the window. I knew there was a reason why the room was so cold.