Schlüter-DITRA 25 - Schlüter-Systems

Schlüter®-DITRA 25

Movement joints:
Schlüter-DITRA 25 must be separated at existing movement joints. If Schlüter-DITRA 25 is used as a waterproofing layer, the joints between the sheets must be covered with Schlüter-KERDI-FLEX band. Movement joints must be continued in the tile covering, as specified by the applicable industry standards. In all other cases, large area floor assemblies installed over Schlüter-DITRA 25 must be subdivided into smaller fields with the help of movement joints. The distance between such control joints in exterior applications (balconies and terraces) should not exceed three metres. Depending on the construction of the substrate, field sizes may need to be smaller. Please refer to our Schlüter-DILEX profile range. Install the corresponding profiles such as Schlüter-DILEX-BT or Schlüter-DILEX-KSBT over expansion joints in accordance with the expected movements. It must be assured that no tension can build at the edge of coverings, e.g. at upright construction elements or floor to wall transitions. The edge profiles and connective joints have to meet the requirements of the corresponding construction  standards and must be suitable to prevent the build up of tensions. Please refer to our Schlüter-DILEX profile range.

Waterproofing with Schlüter-DITRA
By carefully sealing the mat joints and connections with fixtures and walls, Schlüter-DITRA 25 can be used for achieving a waterproofing layer in a tile assembly that is equal to the requirements of the applicable guideline of the German Construction Industry Association, covering the moisture load classifications 0 through C specified therein. 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.

We recommend the use of our waterproofing membrane Schlüter-KERDI (see product data sheet 8.1 Schlüter-KERDI) for applications of Utilisation Class B, "pools." Schlüter-DITRA 25 therefore protects the substrate from damages due to the penetration of moisture and aggressive substances. The abutting joints are covered with the sealing adhesive Schlüter-KERDI-COLL and Schlüter-KERDI-KEBA (minimum width: 12.5 cm) is solidly embedded over the joint. For floor to wall transitions, adhere the Schlüter-KERDI-KEBA in the appropriate width. The sealing band should overlap at least 5 cm.

Schlüter-KERDI-KEBA is also suited for sealing joints with existing fixtures such as door frames, window frames and balcony edge profiles of metal, wood or plastic. Start by applying Schlüter-KERDI-FIX to the part of the fixture that is to be adhered. The remaining width is fully embedded on Schlüter-DITRA 25, using the adhesive Schlüter-KERDI-COLL.

The suitability of Schlüter-KERDI-FIX for the material of the corresponding fixtures must be verified beforehand.

Cut Schlüter-DITRA 25 above structural and seismic expansion joints, then cover the joint with Schlüter-KERDI-FLEX. Schlüter-KERDI-FLEX can also be used for flexible finishing edges. Alternatively, Schlüter-KERDI-KEBA may be used, provided a loose fold is left above the joint.

Floor drains
Schlüter-KERDI-DRAIN is a floor drain specifically designed to allow connections to a bonded waterproofing membrane. This allows the simple and fast connection of Schlüter®-DITRA 25 to the floor drain, using the Schlüter-KERDI collar.
If the material requires an official permit from German authorities, the corresponding test certificate is available upon request.

Substrates for Schlüter-DITRA 25
It must be verified that substrates which are to receive the Schlüter-DITRA 25 matting are even, load bearing, clean and compatible. Bond inhibiting surfaces must be removed. Any unevenness or height and slope differences in the substrate must be levelled prior to the application of Schlüter-DITRA 25.

Concrete is subject to lengthy deformation processes due to shrinkage. Concrete and pre stressed concrete may build up tension because of deflection. Schlüter-DITRA 25 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.

Mortar screeds
With Schlüter-DITRA 25, tiles can be installed on green cementitious screeds as soon as they are ready to bear weight. According to the applicable standards, mortar screeds must cure a minimum of 28 days prior to the installation of tile and their residual moisture content must be below 2% (percentage by volume). In particular, floating screeds and heated screeds tend to change shape or develop cracks after installation, e.g. due to load stresses or temperature changes.

Gypsum based screeds
According to the applicable standards, the residual moisture of gypsum based screeds should not exceed 0.5% (percentage by volume) prior to the installation of tiles. With the application of Schlüter-DITRA 25, tile coverings can be installed as soon as the residual moisture is below 2.0% (percentage by volume).

If required, the screed surface may need to be pre treated (sanding, priming) in accordance with the applicable industry standards and manufacturers' recommendations.

Schlüter-DITRA 25 can be applied using thin-bed tile adhesives that are suitable for the substrate. Schlüter-DITRA 25 protects the screed against moisture penetration from the surface. Gypsum based screeds are sensitive to moisture and must be protected from additional moisture penetration, especially on the underside.

Radiant heated screeds
Schlüter-DITRA 25 may be used over heated screeds as described in the sections on mortar screeds and gypsum based screeds. With Schlüter-DITRA 25, tiles can be heated seven days subsequent to installation. Starting at 77 ºF (25 ºC), the radiant heated floor temperature can be raised gradually by +9 °F (+5 °C) per day, to a maximum of 104 ºF (40 ºC). The air channels of Schlüter-DITRA 25 allow for a quick and even distribution of heat below the tile covering.
For radiant heated floors, we especially recommend our system Schlüter-BEKOTEC-THERM, the ceramic thermal comfort floor. Schlüter-DITRA 25 is also recommended for uncoupling of radiant heated floors consisting of thin electric heating mats. Schlüter-DITRA 25 may be installed either above or below the heating mat. However, the uncoupling function is more effective if Schlüter-DITRA 25 is installed above the heating mat.

Masonry / mixed substrates
Masonry consisting of brick, stone, limestone, cement block, lightweight concrete, or similar is generally a suitable substrate for Schlüter-DITRA 25. Uneven areas must be levelled in advance. Particularly in refurbishments or extensions, different materials (mixed masonry) may be encountered. At the transitions, movement can cause cracks. With Schlüter-DITRA 25, stresses and cracks do not transfer to the tile covering.

Stucco / plaster
Plaster substrates should be examined in accordance with the applicable building codes to ensure they are dry. The surface may need to be pre treated with a primer. Schlüter-DITRA 25 can be applied using thin-bed tile adhesives that are suitable for the substrate.

Balconies / terraces
As an uncoupling membrane, Schlüter-DITRA 25 neutralises the stresses between the substrate and the tile covering that are caused by the frequent and extensive temperature changes occurring on balconies. Furthermore, Schlüter-DITRA 25 serves as a bonded waterproofing assembly together with the tile covering (see notes on waterproofing). The substrate (concrete, screed) must be sufficiently sloped.

For refurbishments, the existing surface assembly can generally remain, provided it is sufficiently sloped and load bearing. Prior to the application of Schlüter-DITRA 25 over existing and cracked tile floors, the loose tiles must be removed and the remaining cavities filled using an appropriate mortar. The preparations also include ensuring a proper slope in the substrate.

We recommend Schlüter-DITRA-DRAIN (see product data sheet 6.2) for coverings with side lengths exceeding 30 x 30 cm.

Rooftop terraces
Rooftop terraces over enclosed living or occupied spaces below are subject to the applicable standards and building codes for roof construction and must feature the required insulation to serve as vapour barrier, heat insulation and top insulation. A drainage system such as Schlüter-TROBA or Schlüter-TROBA-PLUS must be installed over this top insulation layer. This is then topped with screed to act as a load distribution layer. Schlüter-DITRA 25 is installed over this screed as an uncoupling layer with the tile covering and as a moisture barrier for the screed. As an uncoupling mat, Schlüter-DITRA 25 neutralises the stresses between the substrate and the tile covering that are caused by the frequent and extensive temperature changes occurring on terraces.

We recommend Schlüter-DITRA-DRAIN (see product data sheet 6.2) for coverings with side lengths exceeding 30 x 30 cm.

Synthetic flooring and surface coatings
In principle, 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 Schlüter-DITRA 25 matting. The compatibility of the adhesive for the substrate and Schlüter-DITRA 25 must be verified ahead of time.

Plywood, chipboard and oriented strand board (OSB)
These materials are particularly prone to deformation under the influence of moisture (or significant changes in atmospheric humidity). The plywood, chipboard or OSB panels used in construction should therefore be exterior grade. In principle, plywood and OSB can be used as backing materials for Schlüter-DITRA 25 on both floors and walls in interior applications. The thickness of the panels must be sufficient to ensure stability in conjunction with a suitable supporting construction. Attach the panels with screws set at the required minimum spacing. The joints must feature tongue and groove connections and should be secured with additional adhesive. Movement joints of at least 10 mm must be left at the transition to other construction parts. Schlüter-DITRA 25 neutralises the stress occurring in the tile covering and prevents the penetration of moisture.

Structural plank subflooring
Sufficiently load bearing structural plank subflooring in tongue and groove construction, with the appropriate screws in place, is suited in principle as a substrate for ceramic tiles. The timber substrate should have reached the equilibrium moisture content prior to installing Schlüter-DITRA 25. However, an additional layer of plywood panels is recommended. Uneven floors must be levelled using an appropriate levelling compound.

Bituminous screed (paving grade asphalt)
Schlüter-DITRA 25 allows for the installation of ceramic coverings on standard weightbearing, unheated mastic asphalt screeds in indoor areas. The surface needs to be sanded or must be suitable to allow for the proper adhesion of the thin-bed tile adhesive for the installation of Schlüter-DITRA 25.

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