Remove or perforate original vapour barrier?
Ok, one more question: If I'm going for an applied waterproofing agent - Kerdi, or a paint-on over backerboard, do I remove or perforate the original vapour barrier? One section of the shower - only around 2-3' x 1' - is on an outside wall. Should I do this, or should it remain as part of the building envelope? It would effectively sandwich the backerboard between waterproof membranes.