Waterproofing System

Application and Function
Schluter®-DITRA is a polyethylene membrane with a grid structure of square cavities, each cut back in a dovetail configuration, and an anchoring fleece laminated to its underside.

Designed for ceramic tile and dimension stone installations, Schluter®-DITRA serves as an uncoupling layer for problematic substrates, a waterproofing membrane, and a vapor pressure equalization layer to accommodate moisture occurring at the underside of the substrate.

To bond Schluter®-DITRA, use a bonding mortar that is appropriate for the substrate. Apply the mortar using a 1/4" x 3/16" (6 mm x 4.5 mm) V-notched trowel. The anchoring fleece on the underside of Schluter®-DITRA must be fully engaged in the mortar to provide a mechanical bond to the substrate. Using the thin-bed method, set the tile covering directly on the Schluter®-DITRA in such a way that the tile adhesive becomes mechanically anchored in the square, cut-back cavities of the Schluter®-DITRA matting. Schluter®-DITRA is also suited as a support matting for covering materials such as stucco, plaster, or screed.

NOTE: For installation information on the earlier “corrugated rib” design of Schluter®-DITRA, please contact your Customer Service Representative.


Summary of Functions
a) Uncoupling
Schluter®-DITRA uncouples the floor covering from the substrate and prevents the transfer of stresses to the tiled surface. Thus, stresses caused by deformation of the substrate are neutralized. Likewise, stress cracks in the substrate are bridged and are, therefore, not transferred to the surface covering.

b) Waterproofing
Schluter®-DITRA is a polyethylene waterproofing membrane with a very high vapor diffusion density. Provided the seams, floor/wall connections, and connections to building fixtures are properly installed, Schluter®-DITRA creates a waterproofing layer for installations not exposed to constant water pressure. Thus, Schluter®-DITRA protects the substrate against damage due to moisture penetration and aggressive or harmful substances.

c) Equalization of vapor pressure
The interconnected air channels between the cavities on the underside of the Schluter®-DITRA matting remain open. This allows moisture in the substrate to evaporate, thus neutralizing vapor pressure.

Schluter®-DITRA is a polyethylene sheet with a grid structure of square cavities, each cut back in a dovetail configuration. An anchoring fleece is laminated to the underside. The rib height is approximately 1/8" (3 mm).


Material Properties and Areas of Application
Schluter®-DITRA is flexible and bridges cracks. In addition, it does not rot. It is highly resistant to solutions containing salts, acids, and alkalis, as well as many organic solvents, alcohols, and oils. Its resistance to specific stresses can be provided if concentration, temperature, and exposure time are known. Its imperviousness to steam is very high. The material is physiologically safe. It must be verified that substrates which are to receive the Schluter®-DITRAare clean, even, and load bearing. Bond-inhibiting surfaces must be removed prior to the application of Schluter®-DITRA.
Notation: The contact surface of Schluter®-DITRA amounts to approximately 50% of the total surface. This can reduce the load-bearing capacity in case of point loads. For high point loads, select a tile thickness that can distribute the loads. The tile dimensions should be at least 2" x 2" (5 cm x 5 cm).
Suitable substrates for Schluter®-DITRA Concrete
Concrete is subject to deformation due to shrinkage. The time period over which this occurs is 6 to 12 months. Laying tiles on green concrete using the thin-bed method is not possible unless additional measures are taken. Schluter®-DITRA absorbs inherent stresses between the concrete and tile covering so that the tile can be installed as soon as the concrete is hard enough to be walked upon, usually within 2 to 3 days. For wall applications, Schluter®-DITRA can also be used as a support matting for stucco, plaster, or similar.
Post-tensioned, pre-stressed, and lightweight concrete
In addition to the physical characteristics of concrete, post-tensioned, pre-stressed, and lightweight concrete slabs are subject to many other sources of strain or shape deformation; for example, concrete deflection, vibration, and unrelieved shrinkage. Therefore, the direct bonding of tiles (a force-conductive bond) to these structures or substrates is not recommended. Schluter®-DITRA, through its uncoupling and supporting functions, allows the permanent and reliable installation of rigid surface coverings, such as ceramic tile and natural stone, over these substrates. Verify that the slab is even and sufficiently load bearing.
Mortar screeds / Radiant-heated screeds
As a rule, mortar screeds must cure a minimum of 28 days prior to the installation of tile so that deformation due to shrinkage subsides. Floating screeds and, in particular, heated screeds tend to change shape or develop cracks even later, e.g., due to load stresses or temperature changes. With Schluter®-DITRA, tile can be installed as soon as the screed can be walked upon. Seven days subsequent to installation, the radiant-heated floor temperature can be raised gradually by +9 °F (+5 °C) per day.

Comfort floors heated with thin mat or wire systems
Generally, electric heating cables or mat systems are applied directly to the substrate prior to installing Schluter®-DITRA. This allows Schluter®-DITRA to effectively isolate the tile covering from the heated substrate, thus preventing thermal stresses from damaging the tile surface. Schluter®-DITRA will not inhibit heat transfer or reduce the efficiency of the heating system. Note: Schluter®-Systems does not recommend using these systems in wet areas unless recommended by the heating system manufacturer and/or approved by local building codes.

Gypsum-based screeds
As a general rule, when installing tile over gypsum screeds, the residual moisture should not exceed 0.5% (percentage by volume). With the application of Schluter®-DITRA, tiles can be installed even if the residual moisture is approximately 2.0% (percentage by volume). Schluter®-DITRA can be applied using dry-set mortar or other tile adhesive suitable for the substrate. Schluter®-DITRA allows residual moisture from the substrate to condense in the interconnected air channels between the cavities on the underside of the matting and evaporate gradually; moreover, it prevents moisture penetration from the surface.

Note: Since a proper bond to the substrate must be obtained, please follow the manufacturer's recommendations regarding primers, special surface preparation, or setting materials.

Masonry consisting of brick, stone, limestone, cement block, lightweight concrete, or similar is generally a suitable substrate for Schluter®-DITRA. Uneven areas must be leveled in advance. Particularly in renovations or additions, different materials (mixed masonry) may be encountered. At the transitions, movement can cause cracks. With Schluter®-DITRA, stresses and cracks do not transfer to the tile covering.

Balconies / Balcony renovations
Schluter®-DITRA, in conjunction with the tile covering, can be used to waterproof balconies that do not have enclosed living space below. Stresses, which frequently occur on balconies between the substrate and the tile covering (due, primarily, to temperature changes), are neutralized by Schluter®-DITRA. For renovations, the existing surface assembly can generally remain, provided it is sufficiently sloped and load bearing. Prior to the application of Schluter®-DITRA over existing and cracked tile floors, the loose tiles must be removed and the remaining cavities filled using an appropriate mortar.

Note: For plywood substrates, an additional layer of 1/2", exterior-grade, cement backerboard should be installed prior to installing Schluter®-DITRA. For exterior decks over occupied living space, please contact Schluter®-Systems for proper installation guidelines (USA: 800-472-4588; Canada: 800-667-8746).

Existing tile floors
Loose tiles must be removed prior to the application of Schluter®-DITRA. Fill the remaining cavities using an appropriate mortar.

Synthetic flooring and surface coatings
Fundamentally, the surface must be load bearing and prepared in such a way that a suitable tile adhesive will adhere to it and anchor the fleece on the underside of the Schluter®-DITRA matting.

Resilient flooring
Cushioned vinyl or perimeter bonded vinyl flooring must be removed prior to installing Schluter®-DITRA. Make sure all loose adhesive is removed from the surface and verify that a good bond to the substrate can be achieved. For cut-back adhesive residue, verify that the thin-set manufacturer's mortar is compatible. Applications over existing, well adhered, vinyl flooring is possible; however, these applications require special preparation. Please contact Schluter®-Systems for proper installation guidelines (USA: 800-472-4588; Canada: 800-667-8746).
Plywood and Oriented Strand Board (OSB)
Plywood and OSB can be used as backing materials for Schluter®-DITRA on both floors and walls. For single-layer plywood subfloors installed over 16" (400 mm) o.c. joists, use 5/8" (16 mm) minimum, exterior-grade plywood or OSB panel. For single-layer plywood subfloors installed over 19.2" (480 mm) o.c. joists, use 3/4" (19 mm) minimum, exterior-grade plywood or OSB panel. Please refer to method F148-01 in the Tile Council of America's (TCA) 2001 Handbook for Ceramic Tile Installation and/or Method 313F-2000(D) in the TERRAZZO, TILE AND MARBLE ASSOC. OF CANADA (TTMAC) 2000 Specification Guide 09300 Tile Installation Manual.

Note: This configuration is not intended for natural stone surface coverings. For natural stone surface coverings, use a double wood floor. It is the responsibility of the tile contractor to verify that the substrate is even and sufficiently load bearing and, depending on the joist spacing and type of surface covering, decide if an additional layer of wood is required.

I-joists and floor trusses
When I-joist or truss spacing is greater than 19.2" (480 mm), use a double wood floor, consisting of 3/4" (19 mm) tongue-and-groove, exterior-grade plywood or OSB panel, with an overlay of 3/8" (9 mm) minimum, exterior-grade plywood or OSB. 1/8" (3 mm) spacing is recommended between all panels. Please refer to method F147-01 in the Tile Council of America's (TCA) 2001 Handbook for Ceramic Tile Installation and/or Method 313F-2000(D) in the TERRAZZO, TILE AND MARBLE ASSOC. OF CANADA (TTMAC) 2000 Specification Guide 09300 Tile Installation Manual.

Structural plank subflooring
For structural plank subflooring, an additional layer of plywood or OSB should be installed prior to installing Schluter®-DITRA. Uneven floors must be leveled using an appropriate leveling compound prior to the installation of Schluter®-DITRA.



Waterproofing with Schluter®-DITRA
By carefully sealing the matting seams and connections, Schluter®-DITRA can be used for waterproofing in applications not exposed to constant water pressure. For seaming Schluter®-DITRA, adhere the 5" (12.5 cm) -wide Schluter®-KERDI-BAND using a dry-set mortar. For floor/wall connections, adhere the Schluter®-KERDI-BAND in the appropriate width, 7-1/4" (18.5 cm) or 10" (25 cm), using a dry-set mortar. Firmly embed the Schluter®-KERDI-BAND in the adhesive in such a way that it adheres to the DITRA on the floor and directly to the wall substrate. Connections to fixed building elements can be made using the Schluter®-KERDI-BAND. A suitable adhesive or an epoxy mortar that will adhere to the fixed building element shall be applied to the adhesion surface area. Embed the Schluter®-KERDI-BAND in the fresh adhesive, ensuring full coverage. The remaining width shall be bonded completely to Schluter®-DITRA using dry-set mortar. When anticipating large amounts of water, an impervious mortar (e.g., epoxy mortar) can be used to adhere the Schluter®-KERDI-BAND. Cut the Schluter®-DITRA above structural and seismic expansion joints; then cover the seam with Schluter®-KERDI-BAND or Schluter®-KERDI-FLEX, leaving a loose fold above the seam. Where flexible corner joints are required, apply Schluter®-KERDI-FLEX or Schluter®-KERDI-BAND with a loose fold above the joint.

Floor drains
Schluter®-KERDI-DRAIN is a floor drain specifically designed to allow connections to a bonded waterproof membrane. This allows the simple connection of Schluter®-DITRAto the floor drain. At connections to Schluter®-KERDI-DRAIN, Schluter®-DITRA must be held back to the outer edge of the bonding flange. Adhere a 20" x 20" (50 cm x 50 cm) cut section of Schluter®-KERDI to the top of the DITRAmembrane and bonding flange using a dry-set mortar. With the flat side of the trowel, firmly press Schluter®-KERDI into the adhesive to ensure 100% coverage and a watertight seal. Please refer to method B422-01 in the Tile Council of America's (TCA) 2001 Handbook for Ceramic Tile Installation.

Note: KERDI-DRAIN is CSA-approved, standard B79-94, File #211355.


1. The substrate must be clean, even, and load bearing.
2. The type of bonding mortar used to apply Schluter®-DITRA depends on the type of substrate. The mortar must bond to the substrate and mechanically anchor the fleece on the underside of the Schluter®-DITRA.
3. Apply the bonding mortar (mixed to a fairly fluid consistency) to the substrate using a 1/4" x 3/16" (6 mm x 4.5 mm) V-notched trowel. The direction in which the mortar is combed does not affect the adhesion or function of the Schluter®-DITRA. Estimated thin-set coverage to bond DITRA to the substrate is 175 - 200 ft2 (16.3 - 18.6 m2) per 50-lb (22.7 kg) bag of mortar.
4. Individual courses of Schluter®-DITRA are cut to size. Solidly embed the anchoring fleece on the underside of Schluter®-DITRA in the mortar so that its entire surface is bonded (please observe the open time of the bonding mortar). Work Schluter®-DITRA into the mortar using a float or screed trowel. When initially positioning Schluter®-DITRA, it is advisable to align and position the matting while slightly stretching it. Application is made easier with a second person. The side edges and ends of individual courses are cut straight and abutted.
5. Once installed, the matting must be protected against heavy mechanical loads to avoid loosening it from the substrate or other damage. It is advisable to place running boards to protect the Schluter®-DITRA.
6. Immediately after the DITRA matting is installed, the tiles can be set using the thin-bed method. Using a notched trowel that is matched to the type and format of the tile, apply the bonding mortar in a single process. Solidly embed the tiles in the setting material, making sure to achieve full coverage. Please observe the open time of the adhesive. Estimated thin-set coverage to bond tile to the DITRA using a 1/4" x 3/8" (6 mm x 10 mm) square- or U-notched trowel is 60 - 65 ft2 (5.6 - 6.0 m2) per 50-lb (22.7 kg) bag of mortar.
7. Schluter®-DITRA does not eliminate the need for movement joints within the tiled surface. Movement joints should be installed at the usual intervals in accordance with industry standards and norms. We suggest using the Schluter®-DILEX profile series. Schluter®-DITRA is separated at expansion joints. If used as waterproofing, the butt joints must be covered with Schluter®-KERDI-FLEX or Schluter®-KERDI-BAND. Schluter®-DITRA is not separated at control joints; however, control joints are carried over to the tile covering. Regarding structural and seismic expansion joints, please contact Schluter®-Systems for proper installation guidelines (USA: 800-472-4588; Canada: 800-667-8746).

Note on modified dry-set mortars
The dry-set mortar, which is sandwiched between the two impervious layers formed by the DITRA mat and the tiles, can only release its excess water (mixing water, which has not been chemically bonded during curing) very slowly through the joints of the tile covering; the remaining moisture is stored for a long time. The curing process in weather-exposed coverings is frequently interrupted by rain, remoistening the dry-set mortar through the joints. Consequently, the dry-set mortar never dries completely in weather-exposed areas. However, the fine-pored capillaries and hollow spaces can only absorb and store small quantities of water. This is not a problem with dry-set mortars, because the free calcium hydrates are chemically bonded to free water molecules in the mortar matrix. Therefore, dry-set mortars are able to cure through chemical reaction even in the presence of large amounts of moisture. The remaining “excess water” does not damage dry-set mortars, which assures the functionality of the bonded assembly system formed between DITRA, the dry-set mortar, and the tiles.

There are dry-set mortars on the market that have been modified with "flexible" synthetic additives. Depending on the type and material of the synthetic, these mortars are either gauged with water or with a synthetic emulsion to a paste-like consistency and only form a complete film-like layer (harden) when all excess water has been released from the dry-set mortar. As detailed above, this is impossible in the case of weather-exposed coverings. Since complete curing is not achieved through chemical reaction, but as a consequence of drying, i.e., complete water release, some of these modified mortars may never reach the intended hardened condition.

Additionally, even after fully curing, some synthetics re-disperse (return to a paste-like consistency) under the influence of water and may dissolve the mortar structure and damage the bond with the tile. Flexible rapid-setting adhesives have the advantage of drying faster and bonding more mixing water, which results in less excess water and better "film-formation" of the synthetics. Therefore, dry-set mortars which meet the standards of ANSI A-118.1 (those that do not contain flexible synthetic additives), meet all requirements for weather-exposed tile coverings in combination with Schluter®-DITRA. Tiles should be laid in such a way that 95% coverage is achieved to attain a securely bonded covering with a minimum of hollow spaces. Curing time of the mortar must be observed per mortar manufacturer's requirements.

Note: At the time of applying the dry-set mortar, the DITRA mat must be completely dry; i.e., no water should be contained in the square, cut-back cavities.

The combination of such dry-set mortars and DITRA is sufficient for bonding porcelain tiles. Since DITRA uncouples the covering from the substrate, it compensates for deformation stresses caused by differential movement between the substrate and the tile, as well as moisture-related stresses occurring in the substrate below, thereby reducing the bond strength requirement.

The DITRA system has been proven with these dry-set mortars for more than 15 years. Synthetically modified dry-set mortars should only be used if they are specifically characterized as resistant to water, frost, and weather in the product data sheets provided by the manufacturer, or if the manufacturer guarantees these properties upon request. Naturally, the tile materials used for the covering must also be resistant to frost and weather.

Note on exterior installations
Because of the relative difference in expansion between DITRA and certain substrates, it is recommended that DITRA be allowed to adapt to ambient air temperature before installing. Additionally, if large fluctuations in temperature are expected during the installation process, it is recommended that a rapid-setting, thin-set mortar be used to install DITRA.

Item Number Measurements
DITRA 30 3'3" x 98'5" = 323 ft2 (1 m x 30 m = 30 m2)
DITRA 5M 3'3" x 16'5" = 54 ft2 (1 m x 5 m = 5 m2)

Item Number


Width Length
KEBA 100/125 4 mil 5" - 12.5 cm 98'5" - 30 m
KEBA 100/185 4 mil 7-1/4" - 18.5 cm 98'5" - 30 m
KEBA 100/250 4 mil 10" - 25 cm 98'5" - 30 m
Schluter®-KERDI-BAND 5M
Item Number Thickness Width Length
KEBA 100/125/5M 4 mil 5" - 12.5 cm 16'5" - 5 m
KEBA 100/185/5M 4 mil 7-1/4" - 18.5 cm 16'5" - 5 m
KEBA 100/250/5M 4 mil 10" - 25 cm 16'5" - 5 m

Item Number


Width Length
FLEX 125/30 8 mil 5" - 12.5 cm 98'5" - 30 m
FLEX 250/30 8 mil 10" - 25 cm 98'5" - 30 m
125 5M
8 mil 5" - 12.5 cm 16'5" - 5 m
FLEX 250/5M 8 mil 10" - 25 cm 16'5" - 5 m
Schluter®-KERDI-KERECK (Corners)
Item Number Packaging
KERECK 110/5 10 inside + 5 outside corners
KERECK 2I/2A 4 inside corners + 2 outside corners
Schluter®-KERDI-KM (Pipe Collar)
Item Number Packaging
KM 5117/22 10 units (diameter = 7/8" - 22 mm)
Home  |  Contact  |  About us  |  System  |  Portfolio  |  Estimate  |  Store  |  Site Map