Installers regularly contact Schlüter-Systems for technical clarification when working with tiled floors, wetrooms and underfloor heating. Below, the company’s technical team presents some step-by-step guidance to help installers achieve compliant, long-lasting installations.
Step 1: Choosing the Correct Adhesive
For bonding Schlüter membranes to a suitable substrate, always use a cement-based adhesive classified as C2 or C2F S1. This same adhesive can be used above Schlüter-DITRA to both fill the cavities and fully bed the tile or stone in a single application, as long as the adhesive bed does not exceed 10mm. Always check compatibility with the tile or stone manufacturer. Please note, our Peel & Stick membranes do not require adhesive.
Step 2: Understanding DITRA-HEAT & DITRA-HEAT-DUO
Both systems provide uncoupling, waterproofing, and load distribution. DITRA-HEAT-DUO includes an additional 2mm thermal break fleece, improving heat-up times and reducing impact sound by up to 13dB. It can also be installed without heating cables when sound reduction and uncoupling are required.
DITRA-HEAT systems are designed as a secondary heat source, providing underfloor comfort. A separate primary heating system is still required to control room temperature.
Step 3: Heating cable and sensor installation
Both floor sensors must be installed within the membrane – one connected to the thermostat and the second left coiled as a backup.
Heating cables must never be cut, as this will permanently damage the system. Cables should be installed at three-stud spacing to ensure safe operation and prevent overheating.
Step 4: Wet areas, showers and waterproofing
Standard DITRA-HEAT can be installed over Schlüter-KERDI-SHOWER trays, but a separate heating loop is required for the remaining floor area. DITRA-HEAT-DUO is not suitable for use over KERDI-SHOWER trays.
When sealing joints and junctions, a minimum 50mm overlap is required using KERDI-KEBA and KERDI-COLL-L to ensure full waterproofing integrity.
Step 5: Substrates, tiles and profiles
When working over timber floor, floorboards should be replaced or over-sheeted with a minimum 15mm exterior-grade plywood. For P5 (green) chipboard, DITRA-HEAT-PS with its self-adhesive backing is recommended.
The minimum tile size for installation over DITRA is 50 x 50mm, with a minimum thickness of 5.5mm.
Image: Schlüter-Systems
