Where the upturned membrane meets the shower curb, I install
prefabricated dam corners, available from the membrane
manufacturer. I apply two 1/8-inch beads (spaced 1/2 inch
apart) of sealant to the pan membrane, then use a trowel to bed
the dam corners into the sealant.
I try to place all fasteners in the top inch of the upturned
edges. If a fastener has to be used below the 1-inch line, I
seal it with a small CPE patch bedded in rubber sealant.
Dam corners (top left) are applied at the curb juncture.
Rubber sealant is applied to the pan membrane and the curb
framing (top right), the dam corner is pressed into the sealant
(bottom left), and the pan membrane is folded tight against the
framing and stapled in place (bottom right).
With the membrane pan in place, I carefully cut around the
bolt heads protruding from the drain, and press the membrane
over all four bolts. Finally, I snug down the bolts and cut a
hole in the membrane to open the pan to the drain.
Testing the shower pan.
To fit the membrane around the
clamping drain, first cut small holes for the flange
bolts (top ) and push the membrane over the protruding
bolts. Then slice the membrane around the inside
diameter of the drain (middle) before bolting the clamp
ring in place (bottom).
I plug the
drain with an expansion-type stopper and fill the pan with
water up to the top of the curb. Local codes may only require a
few hours testing, but I prefer to let the water sit at least
overnight. Sunken tubs with whirlpool jets should be tested
with all pumps running.