The Key to High-Performance Air Cleaning

Innovative Installation Systems for Tile and Stone

Schluter System

Schluter System- FAQ

Q. Why should I use the Schluter-Shower System?

A. The Schluter-Shower System is an integrated family of products that together form a fully bonded, watertight assembly for tiled showers. Unlike shower pan liners in conventional assemblies, bonded waterproof membranes, such as Schluter-KERDI, bond directly to the mortar bed and protect it from becoming saturated with regular use. In addition, KERDI protects wall cavities from vapor penetration. The Schluter-KERDI-DRAIN provides a simple and secure connection to the KERDI membrane at the top of the assembly. Other components include the Schluter-KERDI-FIX sealant, used to treat protrusions through the membrane, and the Schluter-KERDI-SHOWER- ST/-SC/-SR/-SB prefabricated EPS substrates, which can reduce weight and installation time by replacing the mortar bed. The integrated Schluter-Shower System eliminates leaks, reduces the potential for efflorescence and mold growth in the system, and dramatically reduces total installation time to ensure success and make shower installation easier than ever.

Q. My shower isn’t the same size as the Schluter-KERDI-SHOWER-ST tray. Can I modify the tray to fit my shower?

A. Yes. The Schluter-KERDI-SHOWER-ST tray can be cut to size to fit various applications. Ideally, the tray should be cut by equal amounts on all four sides to ensure a consistent height of the first course of wall tile. However, slight differences can typically be made up with thin-set mortar when setting the floor tile. The shower base can also be extended past the perimeter of the shower tray using dry pack mortar.
Note: The Schluter-KERDI-SHOWER-SC curb can be cut to size to fit various applications. In addition, multiple curbs (or cut sections of curb) can be placed consecutively to form longer runs, including angled designs.

Q. What is a water test? How do I perform one on the Schluter-Shower System?

A. A water test is a quality control check performed on any shower installation before setting tile. It basically consists of stopping the waste line with a test plug and filling the base of the shower stall with water to check for leaks. If you are building a barrier-free shower, then you will need to provide a temporary dam (e.g., a 2×4 and silicone sealant) at the threshold. You can quickly check the test plug by filling the pipe and drain with water up to the height of the Schluter-KERDI-DRAIN integrated bonding flange (or a little below). If the plug is watertight, then you can continue filling the assembly. The water level is marked and the assembly is left for a specified amount of time (24 hours is typical). If there are no leaks, the shower passes.
Notes: We recommend waiting a minimum of 24 hours after setting Schluter-KERDI to begin water testing. This will allow the thin-set mortar to reach final set and ensure watertight performance at the seams under normal curing conditions (i.e., room temperature). If temperatures are much lower (e.g., around 50 or 60 degrees), then it is best to wait longer.

Q. What type of thin-set mortar should I use when installing ceramic and stone tile over Schluter-KERDI?

A. Unmodified thin-set mortar is recommended to set ceramic and stone tile over the KERDI membrane.
Portland cement-based unmodified thin-set mortars are dependent on the presence of moisture for hydration in order to gain strength. Since Schluter-KERDI is impervious, it does not deprive the mortar of its moisture. This allows the cement to properly hydrate, resulting in a strong, dense bond coat. In fact, after the mortar has reached final set (usually within 24 hours), unmodified thin-set mortars achieve higher strengths when cured in continually moist conditions.
Exceptions: Certain moisture-sensitive stones, e.g., green marble, or resin-backed tiles may not be appropriate for use in wet areas or may require special setting materials. Please consult the stone supplier and Schluter-Systems for more information. For an acid-resistant covering, use an epoxy adhesive to set and grout the tile. However, do not use epoxy to install the Schluter-KERDI membrane.
Modified thin-set mortar is not recommended to set ceramic and stone tile over the KERDI membrane.
Modified thin-set mortars must air dry for the polymers to coalesce and form a hard film in order to gain strength. When sandwiched between two impervious materials such as Schluter-KERDI and ceramic tile, including porcelain tile, drying takes place very slowly through the open joints in the tile covering. [According to the Tile Council of North America’s Handbook for Ceramic, Glass, and Stone Tile Installation, this drying period can fluctuate from 14 days to over 60 days, depending on the geographic location, the climatic conditions, and whether the installation is interior or exterior]. Therefore, extended cure times would be required before grouting if using modified thin-set mortars between KERDI and ceramic tile, including porcelain tile. If extended cure times were not observed, the results could be unpredictable. This is even more important to consider in wet areas such as showers as there is the additional concern of latex leaching.

Q. What type of thin-set mortar should I use when installing Schluter-DITRA?

A. The type of thin-set mortar used to install Schluter-DITRA depends on the substrate material. For example, to set DITRA over plywood or OSB, a modified thin-set mortar meeting the requirements of ANSI A118.11 is used. To set DITRA over concrete or gypsum, Schluter-Systems recommends an unmodified thin-set mortar meeting the requirements of ANSI A118.1. Please consult the Schluter-DITRA Installation Handbook before beginning your tile project to confirm the proper materials selection.

Q. What type of thin-set mortar should I use when setting tile over Schluter-DITRA?

A. Schluter-Systems requires the use of an unmodified thin-set mortar meeting the requirements of ANSI A118.1 to install ceramic (including porcelain) and stone tile over Schluter-DITRA*. We don’t recommend the use of modified thin-set mortars to set tile over DITRA because these mortars must air dry to cure properly. When sandwiched between two impervious layers such as DITRA and porcelain tile, drying takes place very slowly through the open grout joints. [According to the TCNA Handbook for Ceramic, Glass, and Stone Tile Installation, this drying period can fluctuate from 14 days to over 60 days, depending on the geographic location, the climatic conditions, and whether the installation is interior or exterior]. Therefore, extended cure times would be required before grouting if using modified thin-set mortars between DITRA and ceramic tile, including porcelain tile. If extended cure times were not observed, the results could be unpredictable. This is even more important to consider in exterior applications that are exposed to rain, as there is the additional concern of latex leaching.

*Exception: Certain moisture-sensitive stones, e.g., green marble, or resin-backed tiles may require special setting materials. Please consult your stone supplier and Schluter-Systems for more information. For an acid-resistant covering, use an epoxy adhesive to set and grout the tile.

Q. Can I use a premixed thin-set mortar to install Schluter-DITRA or KERDI and tile?

A. No. Schluter-Systems does not recommend the use of premixed thin-set mortars (mastics/adhesives) in any Schluter-DITRA or KERDI installation.

Our Clients