Application and Function
Schlüter-DITRA 25 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 tile and natural stone installations, Schlüter-DITRA 25 serves as a waterproofing membrane, a vapour pressure equalisation layer to accommodate moisture occurring at the underside of the substrate and an uncoupling layer for problematic substrates.
The substrate must be even and load bearing. To bond Schlüter-DITRA 25, use a bonding adhesive that is appropriate for the substrate. Apply the adhesive using a 3 x 3 mm or 4 x 4 mm notched trowel. The anchoring fleece on the underside of Schlüter-DITRA 25 must be fully engaged in the adhesive to provide a mechanical bond to the substrate. Please observe the open time of the bonding adhesive. Using the thin-bed method and following all applicable industry standards, set the tile or stone covering directly on the Schlüter-DITRA 25 in such a way that the tile adhesive becomes mechanically anchored in the square, cut back cavities of the Schlüter-DITRA 25 matting.
Summary of Functions
a) Uncoupling
Schlüter-DITRA 25 uncouples the floor covering from the substrate and neutralises the tensions between the substrate and the tile covering that result from the varying deformations of the materials. Likewise, stress cracks in the substrate are bridged and are, therefore, not transferred to the surface covering.
b) Waterproofing
Schlüter-DITRA 25 is a waterproof polyethylene membrane with a relatively high vapour diffusion density. Provided the joints, floor to wall transitions and connections to building fixtures are properly installed, Schlüter-DITRA 25 creates a waterproofing assembly with the tile covering that meets the requirements of the mandatory guideline "Recommendations on Waterproofing in Conjunction with Panelling and Tile and Paver Coverings in Interior and Exterior Applications," published by the German Construction Industry Association (ZDB). Exclusively use system approved thin-bed mortars for areas that require CE conformity or compliance with the general certificate of national technical approval. Please contact us at the address shown in this data sheet for more details. Therefore, Schlüter-DITRA 25 protects the substrate against damage due to moisture penetration and aggressive substances.
c) Equalisation of vapour pressure
The interconnected air channels between the cavities on the underside of the Schlüter-DITRA 25 matting remain open. This allows moisture in the substrate to evaporate, therefore neutralising vapour pressure.
d) Load distribution (load impact)
The bottom of the square cavities in Schlüter-DITRA 25, which are filled with thin-bed adhesive, directly transfer the load impact on the tile covering to the substrate. As a consequence, tile coverings installed on top of Schlüter-DITRA 25 are highly load resistant. If high traffic loads are expected (e.g. in industrial locations), the tiles selected for the installation must be of the corresponding thickness and pressure stability. The requirements of the mandatory guideline "Ceramic Floor Coverings With High Impact Resistance," published by the German Construction Industry Association (ZDB) must be followed.
In areas with high impact loads, the tiles must be fully embedded in the thin-bed adhesive. The contact surface of Schlüter-DITRA 25 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 is capable of distributing the loads. Ceramic tile coverings should not be exposed to the direct impact of hard objects. The tile dimensions should be at least 50 mm x 50 mm.
e) Adhesive properties
Due to the bonding of the anchoring fleece into the thin-bed adhesive on the underside and the mechanical anchoring of the adhesive in the cut back cavities, Schlüter-DITRA 25 achieves a good adhesion of the tile covering to the substrate (laboratory test values: ~ 0.2N/mm2). Consequently, Schlüter-DITRA 25 can be used for wall and floor coverings. Anchor plugs may be used with wall coverings if necessary.
