Vapour control layer or not in bathroom???

[liam546]

I have a solid brick Victorian house which I have stripped back to brick. I'm renovating the bathroom.

I'm going to be use a metal frame wall lining system which is 25mm deep. I will be insulating the 25mm gap with either celotex or sheeps wool and then fixing moister resistant 12.5mm plasterboard before fixing on tiles which are 25kg psqm in weight (large and heavy).

My question is since this is an bathroom generating a lot of moisture should I be incorporating a vapour control layer?

I've read a lot of conflicting advice on whether I should or shouldn't and I'd i do where I should fix it. For example if I fix just beneath plasterboard some people have said it will trap moisture in the board and itl degrade.

Any advice would me great

 

[Deluks]

If it's moisture resistant plasterboard, how will it degrade?

25mm of sheeps wool is a waste of time, some would say 25mm of celotex is a waste of time too, but it's better than nothing.
Sheet over the lot with polythene before fixing any sort of board. But a cement based tiling board such as aquapanel or hardiebacker would be best.

 

[liam546]

Thank you for the reply. I know 25mm of insulation isn't a lot but I don't want to lose anymore floor space than I already am so although I know it will not reduce the U value much at least as you say it's better than nothing.

In terms of the boards I've had MR boards and hardiebacker recommended. How are they different in terms of properties and why would you perhaps suggest a cement board such as hardiebacker over MR gypsum board?

And you defo recommend a VCL such as a polythene sheet on all walls. I didn't go with a VCL on the ceiling as I have plenty of ventilation in the roof space and an extraction unit in the bathroom too. I was hoping this ventilation in the roof space would stop any condensation occurring

 

[freddiemercurystwin]

You don't need a VB behind the wall boards. Use Aqauapanel or hardibacker because its far more resilient to the effects of damp, it should be mechanically fixed.

Aquapanel etc is only really necessary behind the shower or where water will get repeatedly splashed onto the tiles, otherwise MR PB will suffice.

But fundamentally your tiling and grouting should be top notch to prevent board material being an issue!

 

[liam546]

I wanted to avoid cement boards such as hardiebacker as I've read they are awkward to cut and to fix, sometimes having to pre drill holes etc.

My plan was to use gypsum MR plasterboard everywhere and then the gypsum TILEBACKER board that they produce (possibly similar to aqua panel but I don't know)

I would be mechanically fixing all boards to a metal wall lining I'm using.

My only real worry about my plan was whether to have a VB. I thought if I used sheeps wool insulation instead of a board like celotex then it would cope much better of moisture did get through as wool as better properties for dealing with condensation issues as it holds onto moisture and then let's it wick away again. If I went down celotex route I know it's a better insulator per thickness but it's not as good for dealing with potential interstitial condensation

 

[freddiemercurystwin]

Well you seem to know everything so don't know why you bothered posting in the first place.

/hands over baton

 

[liam546]

Sorry - didn't mean to offend. I certainly do not know everything and in fact have very little experience. I've just done lots if reading and so my thoughts above were based on that.

I wasn't really sure on the VB that's all and was just looking for some extra input as I was reading conflicting arguments and couldn't logically come to a decision myself.

I have no idea how much condensation could potentially get into the walls and behind the boards

 

[tony1851]

Don't bother with a VB on the walls, nor with the sheep's wool cr*p -just use the Celotex.

 

[liam546]

Thank you Tony

I won't go with the VB then. Just celotex between the metal frame. Hopefully as it's tight to the wall and I'm using MR board along with a powerful extractor fan. I'm hoping with all the condensation in the walls won't be an issue

 

[Guitar_man]

brick, air gap, frame/battens/celotex, foil backed plasterboard, waterproof tanking on wet areas, tiles. Extractor. Job done.