Installation Guide
INSTALLATION 19
Schluter
®
-DITRA-HEAT membrane and heating cables
INSTALLATION
Preparation
• The substrate must be clean, even, and load bearing. Any leveling of the subfloor must be done prior to installing DITRA-HEAT and DITRA-HEAT-DUO.
• For wood substrates, verify that panels are properly fastened. Tightly butted and/or tented plywood or OSB seams must be addressed prior to installing DITRA-HEAT and DITRA-HEAT-DUO.
If a plywood/OSB underlayment is to be installed, follow the Wood Underlayment guidelines on page 16.
• For vinyl substrates, ensure that the structure beneath is sound and adequate and that the vinyl is well adhered. Remove any wax and clean the surface. For vinyl over wood structures,
nail off floor with ring shank flooring nails every 4" (102 mm) o.c. - fasteners must pass through entire thickness of assembly with minimal penetration into joists.
• For concrete substrates, remove any waxy or oily films and curing compounds (if present) by mechanical scarification. When bonding DITRA-HEAT and DITRA-HEAT-DUO to particularly
dry, porous concrete, the slab should be moistened to saturate the concrete and help prevent premature drying or skinning of the bond coat. Excess or standing surface water must be
removed prior to installation.
• For gypsum substrates, residual moisture in gypsum screed must be 2.0% or less before installing DITRA-HEAT and DITRA-HEAT-DUO. Follow gypsum manufacturer’s directions for
additional substrate preparation.
Membrane
Using a thin-set mortar that is suitable for the substrate,
apply the thin-set mortar (mixed to a fairly fluid consistency,
but still able to hold a notch) using the DITRA-HEAT
trowel, or other 1/4" x 1/4" (6 mm x 6 mm) square-
notched trowel.
1
Apply DITRA-HEAT or DITRA-HEAT-DUO to the
floor, fleece side down. Solidly embed the matting
into the mortar using a float, screed trowel, or
DITRA-ROLLER, making sure to observe the open time of
the bonding mortar. If the mortar skins over prior to matting
installation, remove and reapply. Note: It may be helpful to
back roll the DITRA-HEAT matting before installation to help
the membrane to lay flat.
2
When using the DITRA-ROLLER, place a weight (e.g., bags of
mortar/grout or box of tile) not to exceed 75 lbs on the DITRA-
ROLLER shelf. Slowly move the roller from one end of the matting
to the other, slightly overlapping successive passes.
Lift up a corner of the matting to check coverage. Proper
installation results in full contact between the fleece webbing
and the thin-set mortar. DITRA-HEAT-DUO fleece may not
pull up as much mortar from the floor as DITRA-HEAT when
lifted, but full contact can be achieved as shown. Note:
Coverage may vary with mortar consistency, angle at which
the trowel is held, substrate flatness, etc. If full coverage
is not achieved, remove and reapply, making sure to verify
proper mortar consistency and application.
3
Abut end and side sections of adjacent sheets. Note: Aligning
the studs on the top of the matting during installation can help
make subsequent heating cable installation easier.
4
ESTIMATED THIN-SET COVERAGE
To bond DITRA-HEAT and DITRA-HEAT-DUO
to the substrate, using the DITRA-HEAT
trowel, or other 1/4" x 1/4" (6 mm x 6 mm)
square-notched trowel:
Use one 50 lb. (22.68 kg) bag of mortar per
100 ft
2
(9.3 m
2
).
To bond the tile to the DITRA-HEAT, using a
1/4" x 3/8" (6 mm x 10 mm) square- or
U-notched trowel: Use one 50 lb (22.68 kg) bag
of mortar per 40 - 50 ft
2
(3.7 - 4.6 m
2
).
To bond the tile to the DITRA-HEAT, using a 1/2"
x 1/2" (13 mm x 13 mm) square- or U-notched
trowel: Use one 50 lb (22.68 kg) bag of mortar
per 30 - 40 ft
2
(2.8 - 3.7 m
2
).
Planning
For access to the DITRA-HEAT Calculation Sheet and DITRA-HEAT Online Estimator, see www.schluter.com.
• Select DITRA-HEAT and DITRA-HEAT-DUO membrane according to the size of the area to be tiled.
• Select DITRA-HEAT-E-HK heating cable(s) according to the size of the area to be heated and the cable spacing in the DITRA-HEAT membranes (See table entitled HEATING CABLE
SPECIFICATION on page 26 for more details):
• Cable spaced at 3 studs apart is standard
• Cable may also be spaced at continuously alternating 3 stud - 2 stud intervals in isolated areas or over the entire floor. This practice may be desirable to increase heat output
(e.g., over uninsulated on or below grade concrete subfloors) or to consume more cable length in a given area (e.g., when using the standard 3 stud spacing doesn't allow the
selected cable to fit the floor area and respect minimum spacing requirements from walls, partitions, etc.)
• Cable spacing of 4 studs is not recommended, as it can produce inconsistent floor surface temperatures
• For alternative floor coverings (other than ceramic, porcelain and stone tiles) please refer to section entitled "Alternative Floor Coverings" on page 17 for details
• When measuring the area to be heated, be sure to measure accurately. The heating cable CANNOT be cut to fit. The allowable heated area is limited by the minimum required spacing
from fixed elements such as:
• Walls, partitions, and fixed cabinets = 2" (50 mm)
• Heat sources (baseboard heaters or other fixed heating devices, fireplaces, etc.) = 8" (200 mm)
• Forced air heating vents = 4" (100 mm)
• Centerline of toilet drains = 7" (180 mm)
• Drain pipe = 4" (100 mm). With a linear drain, the cable must be 4" (100 mm) from the actual drain pipe and a minimum of 1" (25 mm) from the channel body edges.
• It is helpful to plan the location of a buffer zone, as it is not possible to predict exactly where the heating cable will end. The buffer zone is an area where floor warming is not essential and
heating cable installation is not planned (e.g., behind a toilet or adjacent to a door opening). This area allows for placement of excess heating cable. Heating cables may also be installed 6"
(150 mm) from the wall to create a buffer zone.
• In the case where there is no space left in the buffer zone(s) and there is excess cable, a continuously alternating 3 stud and 2 stud spacing (i.e. 3-2-3-2) between cable runs may be used.
The following must be maintained:
• The minimum spacing from fixed elements mentioned above
• Do NOT install heating cable with a repeating 2 stud spacing or narrower spacing anywhere on the floor
• Not following the above limitations may cause cable overheating and cable malfunction
Note : The areas with 3-2-3 will be noticeably warmer in some cases and the installer should discuss the location of this with the homeowner.
• For more information on installing DITRA-HEAT-E-HK heating cables on 208 V circuits, please see page 33.
• Multiple DITRA-HEAT-E-HK heating cables can be connected and controlled by a single DITRA-HEAT-E thermostat, if the total current is less than 15 amps. The junction box must be sized
according to the electrical code effective in your region, and must consider the possible use of pigtails and the space occupied by the back part of the thermostat.
• Multiple DITRA-HEAT-E-HK heating cables over 15 amps cannot be connected to a single DITRA-HEAT-E thermostat. Additional DITRA-HEAT-E thermostats must be used, or a DITRA-
HEAT-E thermostat may be combined with the DITRA-HEAT-E-RR power modules.
DITRA-HEAT
DITRA-HEAT-DUO