Vapour Barrier behind shower on exterior wall

Old 06-25-20, 10:34 AM
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Vapour Barrier behind shower on exterior wall

I'm installing a shower in a new basement bathroom on an exterior wall (actually corner of two exterior walls). The shower is a kit (Home Depot) with I believe acrylic back and side panels.
I live in northern Ontario, Canada - where the normal building practise is to cover the warm side of walls and the insulation within, with vapour barrier (polyethylene sheet) and then drywall.
The shower manufacturer calls for the side and back panels surrounding the shower to be fixed directly to studs. And I read that it's unwise (even illegal?) to have two layers of vapour barrier next to each other - moisture can get trapped between and have nowhere to go.

So - the wall panels of the shower strike me as a vapour barrier on their own, and therefore should not go up against the polyethylene vapour barrier on the walls behind them. I'm wondering about:

1. removing the vapour barrier from the walls behind the shower, and relying on the shower wall panels themselves to serve as a vapour barrier - this means somehow dealing with the crack at the edges of the shower where the shower panels stop and the vapour barrier starts...


2. leaving the vapour barrier in place on the outside walls, constructing new walls immediately inside the existing walls, and fastening the shower to the new walls . This would create a 3 1/2" space between the walls of the shower and the vapour barrier on the exterior walls. Or even back the new wall another 1/2" or so off the existing outside walls, so the new studs don't contact the vapour barrier on the existing wall behind them, and there is even more room for air and moisture movement.

Can anyone shed any light for me? Thanks for any thoughts!


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