Hi all I have finished building a 5x3m workshop which is made of 2x4 Timbers, wrapped in breathable membrane then batterns on top of that and finally cladding. I now want to start on the inside. This workshop will having some basic heating and will be used all year round. I have already brought celotex to put between the rafters in the floor and ceiling. so I have a few questions : Once I have put celotex in the floor can I just put the osb straight down or should I cover over with polythene sheets first? Same question for the ceiling but I will be plasterboarding this. And for the walls, which again will be plasterboard, I'm planning on putting 100mm polystyrene sheets between the timber (cheaper than celotex) will this be OK? and again should I just plaster board over this or put polythene sheets over first? Many thanks.
Am i right in saying that if you use celotex and it has the silver lining on it, it does not need a vapour barrier?
Oh yes very good point. I didn't even think of that. I guess I don't have to worry about moisture coming from the Timbers themselves??? What about the walls which I plan to insulate with polystyrene? I guess that in itself is water proof. I just don't want the plasterboard to start getting moisture behind it. I will also be adding some air vents... haven't decided what to use yet for that.
Very true... I'll have to tell the wife it was half price ;-) So are you saying that a moisture barrier isn't needed between the insulation and plasterboard?
Polystyrene is about half as effective as Celotex. Per koolpc, I wouldn't skimp. Another option to consider is adding a layer of Airtec (double) over the studwork before plasterboarding...its 4mm thick and would add some useful thermal insulation for relatively little cost. Better just to celotex, or the place I got mine from (Condell in Sutton) stocked Quinn Therm at £1 a sheet less, its the same stuff. As for Vapour Control Layer, I think if you plasterboard and plaster over the celotex/studwork then that acts as a VPL so no need to add VCL for walls or ceiling. But for the floor, I would add a VCL.
search for "vapour barrier" on screwfix, a few options. Would stay away from very thin sheeting, 300 gauge seems to be the thing...like this? http://www.screwfix.com/p/vapour-barrier-green-300ga-2-5-x-20m/12869
Thanks again. I already have half a dozen sheets of plasterboard which aren't foil backed and would like to use them up. I guess using the VCL you have linked to behind the plasterboard wouldn't cause any problems?
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