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.

 

[Dynamite]

Thank you. I did think that the foil tape will provide enough of a vapour barrier especially since I’ve taped the joists too.

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

 

[pops92]

Did my garage the same 3 years ago and has made a massive difference to retaining heat. I use a diesel Air heater and only have to have it on for short periods.

 

[Sachakins]

Fine as it is.
Is the ply boarding even needed. What will it give you
To me it's unnecessary extra weight on the roof.
If its just aesthetics, I wouldn't bother.

 

[trvlr]

I would leave it as it is; unless the aesthetics are important to you. As is the reflective surface (albeit slightly so) will also reflect light downwards?

For my flat fibre glass roof system I fixed the slabs (various bits' 'n pieces in some areas) with panel pins long enough to be driven into the joists below the slabs, and deep enough to be secure and long enough to support the insulation should it decide at any time to shift (downward...)

 

[Fergie 307]

I would leave it as it is; unless the aesthetics are important to you. As is the reflective surface (albeit slightly so) will also reflect light downwards?

For my flat fibre glass roof system I fixed the slabs (various bits' 'n pieces in some areas) with panel pins long enough to be driven into the joists below the slabs, and deep enough to be secure and long enough to support the insulation should it decide at any time to shift (downward...)

Handy as well if you are putting a ceiling under it, to prevent them falling out on your head at a critical moment