jpinthehouse Posted November 20, 2017 Share Posted November 20, 2017 Have decided on frame therm or similar for in between studs with pir over the top,am I right in thinking that the vcl covers studs then batten then pir then plasterboard Link to comment Share on other sites More sharing options...
MikeSharp01 Posted November 20, 2017 Share Posted November 20, 2017 If you are having the PIR on the inside then I think the VCL should cover the PIR then batten's then plasterboard. The VCL essentially stops water vapour moving through it so you don't want water building up in the PIR although it should dry to the inside. Getting the VCL in the right place seems like a bit of an art. There should be others along shortly who are more knowledgeable than me. I will be interested in the outcome. Link to comment Share on other sites More sharing options...
Ian Posted November 20, 2017 Share Posted November 20, 2017 (edited) 2 hours ago, jpinthehouse said: Have decided on frame therm or similar for in between studs with pir over the top,am I right in thinking that the vcl covers studs then batten then pir then plasterboard The basic principal of a VCL is that it should ideally be installed on the warmest side of the wall build-up so @MikeSharp01 is right that it would be best to have the VCL covering the PIR and then your battens to form the gap for your service zone and then the plasterboard. In my own self-build I didn't have a separate VCL layer - instead I taped the foil faced PIR boards together to form my vapour check layer. Edited November 20, 2017 by Ian Link to comment Share on other sites More sharing options...
chrisb Posted December 17, 2017 Share Posted December 17, 2017 I have a related question about VCL positioning: I have a 140mm TF with 120mm PIR factory fitted, OSB, TF200 Thermo membrane, 50mm cavity, brick outer skin. On the inside I realise I need a VCL, and am thinking of using Protec VC Foil Ultra from the same stable as the TF200 unless there is a better / more cost effective option? The real question for me, is how deep do I need to make my service cavity between plasterboard and VCL? I have 20mm already between Foiled PIR and the face of the studs, so by adding 10mm battens, I could fit 35mm deep dry lining boxes in, so long as they went between the studs and not on top of them. The room(s) are only 2.1m wide internally, so I'm keen to keep hold of as much interior space as possible. Is there a reason to maintain the VCL taught across the studs and therefore have a 20mm air gap behind it? Link to comment Share on other sites More sharing options...
Roundtuit Posted December 17, 2017 Share Posted December 17, 2017 PIR varies in thickness, and so does the accuracy of fitting, so you might want to check that you really do have 20mm where you want sockets. I don't see why the vcl has to be taught, other than it might be a PITA trying to fit it 'baggy'. If space is tight, I think I'd work round the room fitting vcl and noggins/25mm metal back boxes at the same time so you can leave a bit of slack where necessary. When the plasterboard is on, you'll have almost 35mm depth for wiring. Link to comment Share on other sites More sharing options...
ProDave Posted December 17, 2017 Share Posted December 17, 2017 The cheapest airtight membrane I could find was Protect Barriair, from Jewsn but not in stock they had to get it to order. Over the normal stud spacing of a TF there is no way you could stretch it tight enough to prevent the socket box pushing it in enough. However you might need to deliberately leave some slack if you need a box very close to the stud. With 11mm plasterboard and a 35mm deep box (I wholeheartedly recommend nothing but Appleby for dry lining boxes) the box will protrude 24mm beyond the back of the PB so with 10mm battens that's just 14mm of give you need. As stated you only have 20mm before it hits the PIR so lets hope you don't hit a thick bit. Link to comment Share on other sites More sharing options...
Miek Posted February 8, 2018 Share Posted February 8, 2018 (edited) With regards to wiring within a service void. What happens when the wire crosses a stud? you could leave a gap in the batten but it will need plating over with a metal protector will it not? (cables less than 50mm depth need protection IIRC) Or do you try and have only vertical drops? That's still a problem in a ceiling though... What do the sparkys do? Edited February 8, 2018 by Miek Spelling Link to comment Share on other sites More sharing options...
ProDave Posted February 8, 2018 Share Posted February 8, 2018 Read up on "safe zones" Cables can run vertically or horizontally from an accessory in the safe zone that it creates, or in the corner or ceiling safe zone. The 50mm deep thing is different and determines if rcd protection is needed or not. I prefer to leave a gap in the service void battens at 450mm and 1150mm from FFL but I have yet to find a joiner kind enough to do that so I usually have to drill the battens. Protector plates are a good idea if you think the guy fitting the plasterboard is so stupid he has never heard about safe zones or cannot see a cable and make an effort to avoid it. Since I am doing all my own plasterbording I have not used them. Link to comment Share on other sites More sharing options...
Miek Posted February 8, 2018 Share Posted February 8, 2018 Thanks Dave I will indeed have a look at safe zones Link to comment Share on other sites More sharing options...
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