Insulation and vapour barrier

No skills · 5 Nov 2013

Hi folks!

I'm looking at using one of the multi foil type insulations (like superquilt) for the garage/workshop, if I used this sort of product do I still need to use a vapour barrier over the top of the stud work and insulation?

The garage itself is single skin dense block, with timber stud work/insulation/plasterboard for the inside lining. The garage walls do get a little damp so I've been careful to allow an air gap between the block and studwork and also not block up the passage of air up to the roof space (floor doesn't seem to get damp, assumed dpm under the floor).

Another thing.. When hanging the plasterboard over this insulation can I use screws? I have read a couple of things that say not to use screws as the threads in the insulation get caught and wind round the screw thread damaging the insulation.

Does anybody have much experience with this type of insulation?

Thanks in advance

MMUK · 6 Nov 2013

Can't comment on the foil types. However, when I did my garage (my motorbike workshop), I lined the walls and floor with builder's membrane stuck into place with blobs of silicone. My 3x2 stud frames were fixed only into the roof joists, I made them a proper tight fit between the pillars. I insulated with 75mm polystyrene as I was on a tight budget at the time (it only cost me around £8 for an 8x4 sheet) and fitted 3/8" ply over the top. The floor I used 2x2 for the frame, made in several sections and insulated with 50mm polystyrene. When bolted together it was completely free floating. I fitted flooring chipboard on this and then laminated over the top (the laminate was a B&Q Value job as a temporary measure until I could afford a proper floor covering but it's still there three years later).

jasonB · 6 Nov 2013

You really need to batten the walls, fit foil and then counterbatten in the opposite direction so that the foil does not get squashed along a whole batten. If you ring shank nail the counter batten to the first batten you can then use plasterboard screws to fix your boards just making sure the length is correct so they don't come out the back of the counterbattens.

Should not need a vapour barrier

RogerS · 6 Nov 2013

As Jason says. This stuff is not as easy as they would have you believe to fit and eats into your wall or ceiling thickness. The jury is out as far as some Building Control people are concerned for this type of insulation. Could you not get hold of some Kingspan seconds?

No skills · 6 Nov 2013

Ack I hadn't considered the counter battening for the ceiling #-o I really dont want to loose much more height as I will loose near 2" doing the floor. Hmmm..

The main reason I was going to use the quilt was price, had been offered some at a very good price. I do like kingspan/cellotex as it cuts nicely and fits a touch easier than the poly I normally use at work. The price however is a bit steep for a building I'm not using 24/7. Need a rethink, shame as I have a bit of time this weekend to work on the garage.

Thanks for the input folks!