Outbuilding hair salon plasterboard

[Chris9787]

Hello guys just looking for some advice here. I have built an outbuilding in my garden so that in the future the missus can use it as a fully operational hair salon. It is a timber frame building with celotex insulation everywhere, wrapped in breather membrane. All done proply. In the style of what's known as a large garden room (the pretty cedar ones you see now and then).
I was pretty confident on everything apart form which plasterboard would suit that environment best, as I know it can cause nasty problems. I am initially thinking of foil backed plasterboard 12.5 thick, to create a vapour controll layer, but as this room of around 20 sqm will be used as a salon I'm concerned about humidity levels from washing and drying hair, and how that will affect that particular plasterboard setup. Does anyone think I need moisture reaistant plasterboard?
Thanks in advance

 

[theprinceofdarkness]

Ceiling? I think that if you ventilate and heat the building so it does not become "sweaty", then ordinary plasterboard would do. The big problem will to properly seal the VCL against air leakage, especially around cables and plasterboard back boxes. There are all sorts of holes in them that will need sealing, including the fixing clamps.
Have you considered the floor?
Frank

 

[Chris9787]

Thanks for input. The windows In it have trickle vents but if I have to I will probably install an extractor fan. What do you mean about properly sealing? I must admit I have limited knowledge on vapour control layers, I thought they were to stop excessive moisture getting into the timber framing, is that correct? And if so surely if there are only verry few breaches in the vcl such as sockets it wouldn't do too much damage? All the wiring by the way is in the frame and or behind the insulation so shouldn't cause any issues with vcl. Plus The building has cavity ventilation behind celotex which extends to the roof which has a continuous vent on two sides and it has a breather membrane to let out any moisture so it shouldn't ever build up should it? My concern was if there's a build up of moisture in the room and it can't get through the foil backed plasterboard will it just destroy the plasterboard?

 

[theprinceofdarkness]

Because the plasterboard is at the same temperature as the room, there will not be any condensation. The problem is with hot damp air that finds its way around the Celotex (cracks /bad joints etc.). As it gets further from the room, it gets colder until the water condenses out of the air and drips of water would appear on the inside of the breather membrane. here it will run down and rot the base of the woodwork.
"All the wiring by the way is in the frame and or behind the insulation" . This means that individual cables have to run through the insulation to get to the back boxes. The common way is to batten out on the VCL, leaving a service void so cables and back boxes do not have to be sealed.
Frank

 

[^woody^]

You need to protect the frame from internal moisture with a vapour check layer - on the pasterbaord or separate. Then you need to deal with internal moisture via adequate ventilation.

You wont need moisture resisting plasterboard.

 

[cjard]

From world to room, have:

Cladding
Breather membrane
Osb sheeting
Stud work filled with insulation
Another insulation sheet (optional)
A vapour control membrane such as Tyvek airguard, taped and glued (graft ipt or sticks like **** are best value, specialist glues like orcon f are allegedly better. f the membrane is airguard reflex (aluminised) then aluminium foil tape will work, otherwise a roll of something like tescon unitape)
25mm battens
Plasterboard

The battens create a void behind the PB to run cables in etc, without punching holes in the vcl. If you're bothered about making holes in it when attaching the battens, run some glue down the batten rear before you attach it

Consider a small heat recovering ventilation system, as it'll save money on heating and ensure the air in there is always fresh

 

[Chris9787]

Thanks everyone for the information. In regards to doing a vcl and then batten, this is what I did plan to do when I started, but after a while started thinking it would be better for the plasterboard to go directly on my studs for strength and to save time. Plus I have put osb on one whole side of the room for reinforcement when putting up shelves etc. anyway the cables are already in now. But where they come through the insulation I have just cut out enough for the box and then pushed that cutout section to the back (recessed it) so the gap is near on non existent. Basically I know I have two options
1. Buy a vcl and fit that trying to seal it as best I can (time consuming. And normal plasterboard

2. buy foil backed plasterboard to kill 2 birds with one stone. (so long as it doesn't cause any problems down the way)

Obviously I would prefer to take option 2 but if everyone thinks that is a bad idea with the information I've given on my makeup, and how I plan to use the building then I may have to reconsider.

I.e ventilation
I do have 50mm void behind celotex for ventilation that goes to the roof which has a continuous soffit vent.
I have the makeup that cjard refers to, bar the vcl of coarse.
And I may consider a heat recovering vent in the future, thanks for reminding me they exist

 

[theprinceofdarkness]

If the Celotex is installed properly it will be air tight, but. . . and its a big but. The outboard cavity is just to let the wooden cladding dry out. With foil backed plasterboard that is a VCL, except for the joints and screw holes, so not much air will get through, but in the end it will cause a problem, don't know if it will be 5 or 30 years.
Frank

 

[Chris9787]

Thanks frank. When I say there's a 50mm cavity I mean
80mm Insulation
50mm cavity
Osb sheathing
Breather membrane
Counter battery cavity for cladding as its vertical.
I have done a lot of research and I'm confident with how I've built it, but obviously not sure about vcl.
What if I use foil tape on the joints of the plasterboard?
And what exactly will the problem be down the line?
Damp?
Mould growth?
Or rot the timber frame?
I am still very confused as to what exactly a vcl actually prevents. Esthetically and or structurally, Some people don't Evan use them and say it's better to let the building breathe, so can someone explain what happens if you do/don't use it. thank Chris