TrueDEK® Linear Foundations

Here are the most frequently asked questions about the TrueDEK® Linear Foundations. If you find that you still have questions after reading through these, contact us and we can help!

How deep is the linear drain cover?

All covers are ½″ deep.

Can I cut a linear foundation?

No, you really shouldn’t. The manufacturer has changed the composition of the base and maintaining its integrity now requires that all edges remain intact.

What do I use to bond tile to the shower foundation?

Use a quality brand of modified thinset mortar mix. Before installing tile, TrueDEK foundations must be coated with Tank/10 waterproofing compound, which improves the bond between the foundation and the modified thinset mortar, and 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. Waterproofing must be completely dry before applying modified thinset mortar.

Do I have to use ARC waterproofing supplies, or can I use different products?

Some waterproofing products will not bond well to the plastic foundation. The waterproofing products ARC carries have proven to work over thousands of installations, and we stand behind them. Using other products may work, but you’ll have to experiment to build the confidence you’ll want to have before laying the tile. Whatever you use has to do the job for the long haul.

Do I need to tape the joints around a shadow box, niche, or built in bench?

Leaving joints uncovered allows more opportunity for water to penetrate your framing structure. In the long run it pays to embed tape over every joint. You’ll never regret it. Remember, most tile and stone are impervious to water, but grout is not.

Can I remodel a TrueDEK shower?

Absolutely. One of the great things about aTrueDEK foundation is that you can remove the original tile or stone, then redo the waterproofing and cover with new tile or stone of your choice. Be sure to repair any damage to the fiber cement board underlayment on the floor or walls before reapplying waterproofing materials.

Is building a wet room expensive?

Great question. Any installation will depend on many factors, including the size and complexity of the room, the time and materials it takes to apply the waterproofing materials, and most significantly, the type of tile or other wall covering you choose. Wet room walls must be covered with some type of waterproof material like tile, stone, or sheets of acrylic, fiberglass, quartz or the like, and as you might guess, the cost of these materials varies widely.

Why would I consider a wet room?

A wet room provides several key improvements over an un-waterproofed bathroom. First, no water can penetrate to the subfloor, preventing rot, mold, and mildew from developing. Second, water cannot leak into rooms below. Third, shower spray can splash into the room and bathers can step out of the shower without having to dry off beforehand. Fourth, washing down the entire room for cleaning is easy and you’ll never worry about water getting into the framing. Fifth, a wet room can expand the maneuvering area beyond the shower, which can be a real advantage for people with disabilities or physical limitations. Sixth, wet room designs can make a small to medium size bathroom feel much more spacious.

What is a wet room?

A wet room is basically an entire bathroom that has been waterproofed. So, in addition to the shower area, the floor throughout the bathroom is waterproofed along with the walls to a height of about 3″ to 4″. All seams and joints in the floor, as well as the floor to wall joints and wall corners, are covered with embedded reinforcement tape.

Can I install two TrueDEK foundations next to each other to make a large shower?

This has been a good solution for some situations. You’ll have to plan for two drains, and two drainage areas with a slight ridge in the middle.

Do I need to support the edges of a foundation that don’t rest on joists?

Setting a TrueDEK on joists requires care and is a critical part of the installation. The entire perimeter of a base must be supported. Additionally, the drain area requires support. Use 2x stock for all support blocking, and make sure all edges are supported by at least 1½” of material. All adjacent subfloor edges also require support.

What is the hole size for the drain connector?

You’ll need to bore a 3-¼″ hole in the TriForm for each drain connector. A piloted hole saw is the easiest and least expensive tool for accomplishing this task. If you look at any of the supplied plugs for the drain recesses you’ll notice they have a dimple centered in the top surface. Position a plug in the drain connector location you intend to use, and drill a ⅛″ diameter pilot hole through the plug and the TriForm using the dimple to locate the drill bit. Now set the plug aside and use your 3-¼″ hole saw, outfitted with a mandrel and pilot drill bit, and bore out the large hole for the drain connector (just use the pilot hole you drilled earlier to guide the hole saw).

What do I use for connecting the linear drain gulley to the drain line?

ARC carries Sioux Chief’s 825 solvent weld shower drain module for 2″ drain line connections. One of these is supplied with each linear drain assembly. You can order additional connectors if you plan to install 2 or 3 drain lines.

Do I need to install these plugs in the unused drain connector spots?

Yes, we do recommend it. Without the plugs, which are supplied with every linear shower base, the drain connector recesses will hold water and gunk from showering, and become an ugly little science experiment. Use silicone caulk to adhere the plugs in place and it will spare you from dealing with a yucky mess later on. Be sure to clean out the recesses with a damp cloth before installing the plugs.

What do I do if my linear foundation is flexing in the middle?

It could be a couple of things. The subfloor or joists underneath might not be perfectly aligned and level. You may have to use a belt sander to take down any high spots on the joists, and use thin wood shims to fill low spots. You can drill countersunk pilot holes in the foundation field and drive screws to pull the former snug to the joists, however, you do not want to squeeze out all the adhesive. Snug is good enough; the adhesive will do the rest.

Do I need to support the edges of the foundation that don’t rest on joists?

Setting a TrueDEK on joists requires care and is a critical part of the installation. The entire perimeter of a base must be supported. Additionally, you must add support around the drain gulley. Use 2x stock for all support blocking, and make sure the base edges and the adjacent subfloor edges are each supported by at least 1½” of material.

Where do I set a level to check my linear base installation?

The perimeter of each base has a flat area for resting a level. Because of the importance of leveling a TrueDEK foundation, consider using several levels to test your installation: a torpedo level for checking the edges, a longer carpenter’s level for going edge to edge, and a bulls-eye level for spot checks.

How level does the TrueDEK linear foundation have to be when it’s installed?

Absolutely level! TrueDEK foundations offer plenty of pitch to speed water to the drain, but every degree that’s lost to an out-of-level installation affects drainage performance.

Are other drain cover colors available?

Not at this time, though adding oil-rubbed bronze has been considered. Stay tuned.

Do I have to use an ARC waterproofing kit?

Many waterproofing products will not bond well to a gel coat foundation. The waterproofing products ARC carries have proven to work and we stand behind them. If you use any other products, you’re on your own.

What size screws do I use to fasten the linear base?

Use #9 or #10 flathead screws that are 2″ to 2½” in length. Choose screws appropriate for the substrate: deck screws for wood and Tapcon-style screws for concrete. We do suggest using coated or stainless steel screws as a bit of insurance against corrosion due to the wet environment.

Do I drill holes for screws?

Yes, you do want to drill pilot holes so that you can screw a former to a substrate or joists. Use a twist drill bit meant for drilling in metal (you’ll likely drill through the mild steel reinforcement tubes just inside the edges of a TrueDEK linear foundation. Countersink each pilot hole so that the screw heads seat slightly below the surface.

Can I get a custom linear base made?

Sorry, no. TrueDEK linear foundations are made by a special process that requires a mold. Building the mold is time consuming and requires a substantial investment. The manufacturer has tried to offer sizes that meet most requirements. Also, because of the pitch requirements for drainage, there are limitations on the size can be made.

Why are there three drain connector spots?

By offering three drain connection locations, an installer can pick the one that best suits the installation to avoid obstacles or to run a drain line. Also, you have the ability to install more than one drain connector to handle high flow showers. Multiple drain connectors can share a common drain line, or, to increase drain capacity even more, you can use separate drain lines all the way to the stack.

Is the drain gulley a separate part?

Each linear foundation is a fully integrated shower base. The drain gulley is part of the mold and is fabricated at the same time as the rest of the base.

What is a TrueDEK Linear foundation made of?

Fiberglass, resin, mild steel tubes to reinforce the edges, and special marine grade plywood.