Hi Experts

 

I have built a new Garden room from timber and shiplap cladding.

I want it insulated and plaster boarded.

I want to use cheaper wool insulation at 100mm.

 

My question is -should i put the plastic barrier between the cladding and the wool insulation or between the wool insulation and plaster board??

Should i use Plastic sheeting??

If so Should i perforate the plastic sheeting?

Should i use breathable membrane instead of plastic??

Edited August 13, 20215 yr by learner

Welcome to the forum.

 

The idea is to prevent water vapour created inside the building from getting through the plasterboard and insulation to the cold structural timbers where it may condense into water causing them to rot. So the vapour barrier should go between plasterboard and insulation.

 

This is a difficult one with a shed.  Depends on the differences in humidity and temperature between inside and outside, if it is heated/cooled and how often people work in it.

I put the vapour barrier on the outside of mine as it is unheated and I very really actually do any work in it.  I also live in a place of high humidity.

My thinking is that keeping moisture out would be most effective rather than the condensation risk.

Worked well.

I’d suggest both ..! Use a roofing type membrane stapled to the outer frame before boarding out to cover the insulation and stop anything getting into it, and then a plastic membrane on the inside. It is one place where the foil bubble wrap type products can add a little insulation and vapour control and are easy to install. Just remember to tape the joints. 

So from outside to inside goes....

Cladding---breathable membrane---insulation---plastic sheet---plaster board

3 hours ago, learner said:

So from outside to inside goes....

Cladding---breathable membrane---insulation---plastic sheet---plaster board

Yep that would work. Also worth considering using moisture resistant PB as it’s not much more in the big scheme of things 

 

6 hours ago, learner said:

So from outside to inside goes....

Cladding---breathable membrane---insulation---plastic sheet---plaster board

 

Yes that's more or less what I built (mine also had a layer of WBP to prevent racking) but didn't you say its already built? So not possible to fit breathable membrane before the cladding.