I'm getting ready to finish waterproofing my new shower before tiling it and am wondering if I should waterproof the mud pan on the floor? My construction methods are as follows from bottom to top:
- Wooden subfloor
- pre-sloped mud pan (with tar paper & metal lathe between the subfloor)
- pvc shower pan liner 6" up the studs & over curb
- Concrete board on walls down to bottom of liner
- Final ~1/2-3/4" mortar bed over the liner and mortared shower curb
I'm going to paint a few layers of liquid waterproofing membrane over the concrete board walls (and should I do the ceiling since I'll be tiling that as well?). Does it matter if I also waterproof the mud floor? I know it's not necessary since that's what the liner is for, but would it hurt anything? I'm mainly interested if there's a concern for hydrostatic pressure buildup between the impermeable PVC liner and the liquid membrane if water were to get in between them somehow.