What type of vapour barrier (if any) for shed/garage roof?

wall

I need some advice, i have searched other questions here but i was getting confused. I am insulating a garage/shed, it has corrugated iron roof, i will be putting insulation up between the rafters and finishing it with 9mm ply. My question is, should i put a vapour barrier up before the insulation and should it be just a roll of plastic sheating or a breathable membrane? Thanks.

BryanF

http://www.environ.ie/en/Publications/DevelopmentandHousing/BuildingStandards/FileDownLoad,18753,en.pdf
see p20-21

felt on the outside
vapour barrier on the inside

wall

felt on the outside
vapour barrier on the inside
[/QUOTE]

So i should put felt up first, then the insulation, then a vapour barrier, then the plywood? Can the vapour barrier be just from a roll of plastic or should it be a breathable membrane?

yop

I think 1000 gauge builders plastic will do the job.

wall

Thanks for the replys. I am going to stud out the walls, fit insulation between the studs and then 12mm ply over it, should i fit plastic behind the ply here also?

BryanF

So i should put felt up first, then the insulation, then a vapour barrier, then the plywood? Can the vapour barrier be just from a roll of plastic or should it be a breathable membrane?

what are you putting in this shed?
have you a heat source?
have you ventilation?
these answers will dictate the type/ importance of using an actual vapour barrier (which allows some moisture through) as opposed to a sheet of plastic that if sealed will capture and retain every drop of moisture

wall

It will be used as a workshop to do some woodwork. There is an oldish wood stove going into it. There is at least one vent in the wall, i'd have to have another look.