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Installing the Shower Pan Liner A shower pan is a waterproofing system that channels water into a drainage system. Since buildings move, shower pans must be able to accommodate movement. In the old days, lead or copper sheeting and hot-mopped shower pans were common, though they were difficult to work with and prone to leaks. For the past 20 years, I’ve been using chlorinated polyethylene (CPE) sheet membrane to fabricate pan liners for showers, sunken tubs, fountains, and other wet tile installations. Available from the Noble Co. (614 Monroe St., Grand Haven, MI 49417; 800/878-5788), CPE membrane, called Chloraloy, comes in 4-, 5-, and 6-foot-wide rolls, and can be bonded to itself to make shower pans of any size. I install blocking between the studs around the entire perimeter of the pan area, making sure the blocking extends at least 1 inch above the upturned sides of the pan, and that all fasteners are countersunk or flush. Local codes will vary, but I typically make the sides 8 to 9 inches high. I make a sketch of the shower floor area and the upturns where the membrane meets any walls or curbs. I unroll the membrane in an open area, reproduce the sketch on the CPE membrane, and cut it to size. Next, I crease the corners, fold up the membrane, and place it on the shower floor for a dry fit.

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After cutting the membrane material to size (top left), the curb edges are folded over (top right) and the entire sheet is rolled up (left) and placed on the sloping mortar subfloor.

When I’m sure of the fit, I refold and remove the membrane, loosely screw the membrane clamping bolts (bolts that clamp the two halves of the drain together) into the lower half of the drain, and run a bead of rubber sealant around the lower drain flange. I use Noble’s proprietary sealant, NobleSealant 150, when working with its CPE membrane. I then reposition the bundled liner over the shower floor and lower it into place. After creasing and folding the excess corner material, I staple it flat to the wall blocking, holding all staples to within an inch of the top edge. I apply sealant between the layers of the corner folds to hold the material tight against the wall blocking.

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NobleSealant 150 is applied to the folded inside corners (left) before stapling them in place (right). On large installations, I install the membrane in several smaller sections, then use NobleSealant 150 to join the pieces together.