Re: vapor barrier
This is a tricky one.
Originally Posted by Vincentx
The paper face on that insulation is only a vapour retarder ( not a barrier ) and considering the method of installation doesn't provide an airtight seal --- combined doesn't provide a very strong barrier for vapour drive into the wall cavity if you are in a cold winter zone.
Tar paper is not a vapour barrier since it highly vapour permable which is why it is used on exterior sheathing. Also , tar paper will disintergrate once it becomes saturated with water and can actually increase potential for mold because of it's paper base.
Considering the insulation is also behind the tub ( running down to the floor ) then putting any type of vapour barrier above the tub really will be useless --- since only half the wall would be sealed. Ideally completely removing the tub and installing a complete vapour barrier over the entire wall would be best, otherwise you're best to leave things as is and use the Kerdi - Board.
This product will be the substrate -- water proofing system for the walls.
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