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Perimeter Membrane

I measured and cut the 14-inch-wide perimeter membrane fabric, leaving enough for about a 4-inch overlap. Then, following the manufacturer’s instructions, I prebent a 2-inch leg along one edge (Slide 14), which I firmly bedded into a double bead of sealant around the base to create a good bond (Slides 15, 16), looking for a continuous line of squeeze-out (Slide 17). After sealing the overlap in the corner (Slide 18), I worked back around the perimeter with the caulk gun, laying additional sealant to thoroughly cover the joint between the wall membrane and the base (Slide 19).

Next I installed the inside corner pieces, using two beads of caulk in continuous rings so that there would be absolutely nowhere for water to seep through (Slide 20). I pressed them into the corners, again looking for squeeze-out and tooling the edge with my finger (Slide 21). The preformed outside corners were next, two per jamb, applied directly to the wood with sealant (Slide 22); again, I used plenty of sealant and tooled the squeeze-out (Slide 23). 


After slitting the perimeter membrane to allow it to fold over the jamb, I squirted sealant onto the preformed corners (Slide 24) and spread modified thinset over the exposed wood — back, top, and front (Slide 25) — then bedded the membrane onto the threshold with my trowel (Slide 26). Where the slit membrane runs up the back of the jamb, which you can’t see in the photographs, I used sealant to create a leakproof bond.

I then measured the polystyrene curb cover that Noble had provided (this does not come with the ProBase kit), cut it to size with a utility knife (Slide 27), and thinset it into place, making sure to get the mortar on both vertical legs as well as the top so that it would have good support (Slide 28). After placing a few plastic-cap roofing nails on the outside of the curb (Slide 29), I applied silicone sealant at the joint at each end of the threshold, per the instructions (Slide 30). Noblesealant 150 is incompatible with the polystyrene.

Finishing Up

I let the sealant and thinset set up, then plugged the drain and performed a water test (Slide 31). In this case, I let the water sit overnight; there were no leaks, so I drained the pan and immediately reinstalled the clamping ring right-side up. The next task was to adjust the final height of the chrome drain cover. I wanted the embossed type on the chrome strainer to be aligned parallel with the threshold, so after covering the drain cap with duct tape to protect it, I marked the orientation with a pencil (Slide 32). I then screwed the chrome plate into the drain assembly, positioned the plastic weep protector around it (Slide 33), and adjusted it so that its orientation was correct (34), checking for correct tile height and slope with a level (Slide 35). Finally, I filled the depression around the strainer with cement mortar — I use the bag form of Laticrete 3701 (Slide 36). At this point, the shower pan is done.

Once the mortar in the base set up, I finished the job by installing Durock cement board on the walls (Slide 37), using cardboard to protect the shower base and also to create a gap at the bottom of the cement board (Slide 38). I used mastic to adhere the Durock to the studs, making sure that the lowest nails in the cement board were no lower than the top inch of the membrane underneath. I taped and mudded all the joints, using fiberglass mesh tape and modified thinset, then applied Laticrete 9235 brush-on waterproofing membrane (Slide 39) and tile (Slides 40, 41).