TrueDEK® Linear Bases

Unibody TrueDEK® Linear shower foundations feature a fully integrated drain gulley molded directly into a structural, pre-pitched base. The drain gulley offers three drain connector locations to ease installation–choose the drain location that avoids obstacles (pipes or joists, for example) or suits plumbing requirements, or choose multiple outlets to manage high volume shower output.

As a structural shower foundation, a TrueDEK Linear base may be installed directly on joist systems spaced 16″ on-center (14½″ apart).  Precisely pre-sloped, each foundation ensures swift and accurate drainage. All TrueDEK Linear models are a ⅞″-thick at the edges, which allows the installer to match them with typical subfloor assemblies prepped for tile or stone. Because the foundations are so thin, expensive joist modifications are unnecessary to achieve a level-entry shower (a costly byproduct of mud bed shower construction).

Cover your TrueDEK Linear foundation with tile or stone, and later, if you want to remodel your shower, it’s a cinch to recover the base–just remove the floor covering, repair the waterproofing, and lay new tile or stone.

TrueDEK Linear foundations are often installed and waterproofed in a single day, and tiling begins the following day. Linear foundations accommodate tile of any size–follow TCNA tile installation guidelines.

Unlike the TrueDEK Classic line, linear bases should not be cut.

TrueDEK foundations are certified by ICC as compliant with the following code authorities: International Residential Code, International Plumbing Code, Uniform Plumbing Code, and the National Plumbing Code of Canada.

TrueDEK Linear foundations provide reliable, completely predictable installations, and performance, making it easier to achieve a beautiful spa-style shower and avoid the risk of leaks and failures common with other shower construction methods. Every foundation is covered by a limited lifetime warranty from the manufacturer.


  • Structural shower foundation with a lifetime warranty
  • Pre-pitched and ready for tile or stone
  • ⅞" thick at edges
  • Integrated drain gulley with 3 drain locations
  • Install on 2× wood joists, truss joists, and TJI joists
  • Flat rim for easier leveling
  • Supports 560 lbs. on joists and typical blocking; up to 1,100 lbs. with complete blocking underneath
  • ICC certified
Contact Us To Order

Ready to tile in 1 to 2 days!

Remove subfloor and add blocking
Remove subfloor and add blocking
Install shower base
Install shower base
Connect drain and seal joints
Connect drain and seal joints
Complete waterproofing
Complete waterproofing
Ready to tile in 1 to 2 days!

Available Models

35½" x 35½"
900mm x 900mm
39⅜" x 39⅜"
1000mm x 1000mm
47¼" x 47¼"
1200mm x 1200mm
51¼" x 32¼"
1300mm x 820mm

Product Specs

Please see product specification sheets for details.

Thickness at edges: ⅞″

Composition: Fiberglass, resin, gel-coat, marine plywood, and mild steel

Slope gradient: Pitches vary in slope, though all pitches are greater than ⅛″ per foot (complies with all applicable codes for a pre-fabricated, structural, tileable shower plumbing fixtures).

Weight load capacity: 560 lbs. on code compliant, 16″ o.c. joist systems and supplemental blocking; 1,100 lbs. on code compliant, 16″ o.c. joist systems, with ¾″- thick plywood filling all spaces between joists and supported by 2× blocking (call ARC for more information).

Stress capacity: 4,000 pounds-force per square inch.

Support requirements: Installation requires supporting the entire perimeter of the foundation and within 2″ around the drain gulley; be sure to support the adjacent subfloor, as well; support can be achieved with joists and supplemental 2× blocking.

Custom fitting:  Do not cut TrueDEK Linear foundations; skilled installers can extend the length or width of the shower foundation by floating additional slope using mortar.

Drilling: For pilot holes, drill anywhere in a foundation using a typical twist drill bit for metal; use a countersink bit or multi-step bit to countersink each pilot hole so that a flathead screw head will be flush or slightly below the surface of the foundation; around the perimeter of the foundation, drill pilot holes 8″ to 10″ apart–keep pilot holes at least 2″ from each corner; you can drill pilot holes in the main drainage area if you think it is necessary to secure the foundation to joists or blocking; for installation screws, 2″-long stainless steel or ceramic-coated screws are recommended.

Adhesive: Always use polyurethane construction adhesive (label must indicate “bonds to plastic and wood”) to install a TrueDEK foundation on wood; for installations on concrete, use modified thinset mortar.

Tile or stone adhesive: After waterproofing has dried completely, use modified thinset mortar to bond tile or stone to the waterproofing membrane.

Drain capacity: A 2″ dia. waste line connection will handle a water flow rate of approximately 6 to 7 gallons per minute (consult a qualified plumber to properly calculate water flow and drainage requirements for a project); shower heads typically generate a flow rate of 1.5 to 2.5 gallons per minute.

What You'll Need

  • TrueDEK Linear foundation
  • drain assembly
  • 2″ drain connector
  • waterproofing kit (additional waterproofing supplies may be required depending on the size and complexity of the project)
  • circular saw
  • flush cutting saw or reciprocating saw
  • power drill
  • belt sander or orbital sander
  • caulking gun
  • 3¼″ hole saw with mandrel
  • hammer
  • pry bar
  • speed square
  • scissors or utility knife
  • 3″ or 4″ paint brush (throw away type)
  • paint roller and cover
  • 2× lumber for blocking
  • polyurethane construction adhesive (four to five 10 oz. tubes)–use a product that bonds to plastic and wood
  • acrylic paintable caulk (one 10 oz. tube)
  • #9 x 2″ ceramic coated or stainless steel flathead screws


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.

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Tank/10 Waterproofing Data Sheet
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Tank/10 Adhesive
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TrueDEK Linear Drain–
solid cover
Download Spec Sheet
TrueDEK Linear Drain–
slotted cover
Download Spec Sheet
Drain Line Connector
Download Spec Sheet
Waterproofing Kits
Download Spec Sheet
TANK/10 Waterproofing
Download Spec Sheet
Joint Reinforcement Tape
Download Spec Sheet
Internal Corner
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External Corner
Download Spec Sheet
Supply Gasket
Download Spec Sheet