As a second-generation tile setter — I started working in my father’s tile business as a teenager — I’ve installed hundreds of shower pans. Tiled shower pans are not something you want to take risks with; leaks are expensive to repair and can cause serious structural damage in wood-framed houses. Years ago we settled on a reliable installation method for tiled shower pans: Chloraloy membrane, from the Noble Co. (noblecompany.com), installed over a sloped subbase, running to a three-part weeping drain, followed by a sloped mud bed. I’ve built shower pans using this method for years and have never had a problem.
There are some new shower-pan systems available that use a surface-bonded waterproofing membrane and skip the weeping drain. I’m not a big fan of these products, though I do occasionally install them when a GC requests it. When I was asked by a local builder to try out the ProBase pan from Noble, I was interested for a couple of reasons. First, I’ve used Noble products for years, including the Chloraloy pan membrane mentioned above, and I’m familiar with their quality. Second, this preformed shower base is designed for use with a clamping drain, so it would provide the backup weep drainage I’m used to. So I accepted the opportunity to install a ProBase kit at a local job and assess it for JLC.
The ProBase kit I installed includes the shower base itself, a plastic weep protector (a product I’ve been using for a while on all my shower pans), a tube of NobleSealant 150, a strip of membrane flashing for the edges, and eight preformed corner flashings — four for inside corners and four for outside corners. The 48-inch-square center-drain kit retails for $593 at Noble’s website; other sizes and drain placements are also available.
The base is very light. It consists of a waterproof sheet membrane laminated to a polypropylene matrix. A depression and cutout in the center allows for placement of the clamping drain.
The first thing I did was place the base on the ground and stomp on it. Reassured of its strength, I also tried to peel the membrane away from the plastic structure, but it held firm. Cutting the base to size was easy. The instructions recommend scoring and snapping the base, as you would do with drywall, but with a product this costly I wanted to make sure I had a clean cut. So I cut first from the top, using a utility knife (Slide 1), then flipped it over and finished cutting from the back (Slide 2).
Setting the Base
The weep drain was already in place. I checked that the floor was level, then nailed down a piece of 1/2-inch-thick Durock cement board in a bed of thinset (Slides 3, 4) over the floor sheathing to bring the surface flush with the drain flange. After fine-tuning the fit of the base Slide (5), I prepared to bond it to the floor, first troweling out modified thinset with a 1/4-inch-by-3/8-inch square-notch trowel (Slide 6), then applying a double ring of Noblesealant 150 (Slide 7) around the drain flange (Slide 8). I set the base into place (Slide 9) and firmly pressed the membrane into the sealant around the drain (Slide 10). Next I cut out the drain center and the bolt holes around the perimeter (Slide 11) so that I could install the top half of the drain while the sealant set up. Note that the bottom of the clamping ring is grooved to allow water to weep into the drain (Slide 12). There are eight holes; four of them are bolt holes, but the other four receive water from the grooves and pass it into the drain. It’s important for these grooves to remain unobstructed, so for now I bolted the clamp ring onto the drain upside-down, flat-side down, so that the sealant and membrane fabric wouldn’t squeeze up into the drainage grooves as the sealant set (Slide 13).