Workshop inside roof

[Dynamite]

Hi everyone, I just wanted to post here to ask what you think about this situation. I am currently insulating my workshop roof and as you can see insulated with Kingspan insulation board I’m now going to ply over this, however I am unsure whether I need to bother with a vapour barrier. I know this is the case for if I was occupying the building for living in it, but I’m not it’s just a workshop and I would like the easiness of having to just put the plywood over the top of the Kingspan. What do you think?

I have attached a picture which shows the Kingspan and I’ve also put a small patch of vapour barrier. However I don’t want the issue of the vapour barrier creating creases and the ply not fitting well to the joists. As you can see in the picture I have put a small part of vapour barrier on and this is when I noticed this could be an issue.

Just so you know, the joist are 100mm and the insulation board is 50mm and I’ve got a 50mm air gap between the top of the insulation board and the bottom of the roof tile membrane.

Kind Regards..........Rob

 

[Doug B]

The foil on the insulation acts as a vapour barrier so why install another one?

 

[niall Y]

You will only really have encountered problems if your roof had been corrugated steel. and there was no membrane directly under it. This coupled with the Kingspan can cause bad condensation with water dripping onto machines on cold frosty days. As long as you have a barrier under the tiles you should be fine.