TrueDEK Classic Bases

All the screws that come with the drain for tile are stainless steel, and they are metric sizes and thread counts. These are available at many well-stocked hardware stores in their specialty fastener section (often you’ll find an aisle with pull-out drawers, and inside the drawers are all kinds of unique fasteners). Here is the screw information:

1. For the four screws that fasten the adaptor to the foundation, you really can use flat head screws that fit, and they don’t have to be metric. We recommend #6 or #8 x ¾″ long, flathead, wood threaded style screws in stainless steel or ceramic coated. Always drill pilot holes before driving these screws.

2. To secure the clamping ring, you’ll need M4 x 0.7 x 16mm long stainless steel screws. These have to be metric and the proper size and threading to fit the threaded holes in the adaptor.

Sorry, we can’t, but there are usually local metal fabricators who can do a great job if you give them a design or tell them what you want. You can also try this online source: www.designerdrains.com.

Use a quality brand of modified thinset mortar mix.

Before installing tile, TrueDEK foundations must be coated with Tank/10 waterproofing compound, which bonds to the plastic shower base and provides an ideal surface for the modified thinset mortar.

Modified thinset mortar will bond directly to the shower base, but it is an inferior bond. Tank/10 waterproofing, on the other hand, bonds very well to the plastic shower base, and it provides an anti-fracture membrane to protect grout and tile from minor movement in the underlayment that may otherwise cause a crack or fissure in the tile layer.

You can trim the edges of any TrueDEK Classic base so that the drain hole ends up in the center, or at least cloer to center. But in their original format, every TrueDEK Classic base except for one has an off-center drain hole. An off-center drain hole allows an installer to rotate the foundation so the drain hole misses a joist or some other obstacle.

Chances are, the blocking you installed to support the drain hole is too close to the hole, so that the reinforcement ring on the underside of the foundation is preventing the foundation from sitting on the joists properly. If you look at the underside of the foundation you’ll see there is a strengthening ring around the drain hole. If the ring or reinforcement area rests on blocking or a joist or some other support, it can prevent the shower foundation from seating properly. As screws are driven around the perimeter of the base, the area around the drain hole will remain raised, resulting in flex when a person steps on the base. This error must be corrected before tiling the shower; if not corrected, grout is likely to crack, tile may pop loose, and water may run away from the drain.

If joists or blocking are uneven, or there are high or low spots on the top edges of joists or blocking, this can also cause flex. You want to achieve even support along every joist, and from joist to joist, while assuring that the foundation is level.

You will see some flex until the base is fully installed with polyurethane construction adhesive and screws, just as you would see with underlayment materials like plywood subfloor, for example.

A Classic foundation that is seated evenly on joists and blocking may flex a little, but once it’s fastened and bonded to the framing structure it becomes very rigid, just like plywood subfloor does when it’s installed on joists.