Use and Care Manual

3
Schluter
®
-DITRA-HEAT
3
Note: Type, thickness, and format of the tile or
stone surface covering must be suitable for the
intended application. Minimum tile format is 2" x
2" (5 cm x 5 cm).
Due to airspace within the assembly, tile or
stone coverings installed over DITRA-HEAT-
DUO membranes may have a hollow sound
when they are walked upon with hard shoes or
tapped with a hard object.
Movement Joints
DITRA-HEAT and DITRA-HEAT-DUO do not
eliminate the need for movement joints, including
perimeter joints, within the tiled surface. Please
refer to the Schluter
®
-DITRA-HEAT Installation
Handbook for movement joint placement
guidelines.
Wood Underlayment
In some applications, adding a layer
of plywood or OSB before installing
DITRA-HEAT or DITRA-HEAT-DUO and the
ceramic or stone tile covering is required to
reduce deflection and curvature of the
sheathing between the joists. Please refer to
the Schluter
®
-DITRA-HEAT Installation
Handbook for plywood/OSB underlayment
installation guidelines.
Thin-Set Facts
Schluter
®
-Systems offers thin-set mortars
designed for use with Schluter
®
membranes
and boards. All Schluter
®
-Systems’ thin-set
mortars, including the ALL-SET™ and FAST-
SET™ modified varieties, can be used to set
tile over Schluter
®
-DITRA, DITRA-HEAT, KERDI,
KERDI-BOARD non absorptive substrates. If
Schluter
®
thin-set mortars are not used, we
require unmodified thin-set mortar when setting
ceramic or porcelain tile over DITRA-HEAT.
Question: Can ceramic tile, including porcelain
tile, be set on DITRA-HEAT or DITRA-HEAT-
DUO with unmodified thin-set mortar?
Answer: YES. In fact, we recommend it.
Here’s why: Portland cement-based unmodified
thin-set mortars are dependent
upon the presence of moisture for hydration
in order to gain strength. Since DITRA-HEAT
and DITRA-HEAT-DUO are impervious, they
do not deprive the mortar of its moisture.
This allows the cement to properly hydrate,
resulting in a strong, dense bond coat. In
fact, after the mortar has reached final set
(usually within 24 hours), unmodified
thin-set mortars achieve higher strengths when
cured in continually moist conditions.
Question: Can ceramic tile, including porcelain
tile, be set on DITRA-HEAT and DITRA-HEAT-
DUO with latex-modified thin-set mortar?
Answer: In general, we DON’T recommend it.
Here’s why: Latex-modified mortars must
dry for the polymers to coalesce and form
a hard film in order to gain strength. When
sandwiched between two impervious materials
such as DITRA-HEAT or DITRA-HEAT-DUO
and ceramic tile, including porcelain tile, drying
takes place very slowly through the open joints
in the tile covering. [According to the TCNA
Handbook for Ceramic, Glass, and Stone Tile
Installation, this drying period can fluctuate from
14 days to over 60 days, depending on the
geographic location, the climatic conditions,
etc.]. Therefore, extended cure times could be
required before grouting if using modified thin-
set mortars between DITRA-HEAT or DITRA-
HEAT-DUO and ceramic tile, including porcelain
tile. If extended cure times were not observed,
the results could be unpredictable.
Question: Can Schluter ALL-SET™ and
Schluter FAST-SET™ modified thin-set mortars
be used to set tile over Schluter boards and
membranes?
Answer: Yes. All Schluter
®
thin-set mortars,
including the ALL-SET™ and FAST-SET™
modified varieties can be used to set tile over
DITRA, DITRA-HEAT, KERDI, KERDI-BOARD
non absorptive substrates.
Question: How is this possible?
Answer: The key is predictability. Schluter
Systems’ modified thin-set mortars have been
specifically formulated to set and gain strength in
a timeframe that fits typical installation practice,
even when sandwiched between Schluter
®
membranes or boards and porcelain tile. The
proportions of cement, water-retention agents,
polymers, and other components in the mixtures
were balanced to ensure that extended dry times
are not required. This was validated through
both laboratory and practical testing. Now, the
installer can select from either unmodified or
modified thin-set mortar to install tiles within our
systems according to his or her preference.
Question: Why did Schluter Systems change its
position on thin-set mortar?
Answer: We haven’t changed our position
on thin-set mortar use within our systems.
Developing our own setting materials has given
us the ability to guarantee consistently positive
results. And since we control the formulas, we
can be sure no changes will be made that have
a negative impact on setting times and strength
gain in these environments.
Question: Does this mean I can use other
manufacturers’ modified thin-set mortars to
install tile over Schluter boards and membranes?
Answer: No. Our position on thin-set mortar use
within our systems in general has not changed.
We have no control over the formulation of other
manufacturers’ products and therefore cannot
guarantee consistently positive results with their
modified thin-set mortars.
Question: Can I still use other manufacturers’
unmodified thin-set mortars to install tile over
Schluter boards and membranes?
Answer: Yes. We still warrant the use of
unmodified thin-set mortar meeting ANSI A118.1
to install tile within our systems because we
have confidence in the performance of this
product category. This is based on the science
of cement hydration and years of positive testing
and field experience.
Please note, if Schluter
®
thin-set mortars are
used with Schluter membranes an extended
system warranty is available.
Additional Notes:
Remember, the type of mortar used to apply
DITRA-HEAT or DITRA-HEAT-DUO depends on
the type of substrate. The mortar must bond to
the substrate and mechanically anchor the fleece
on the underside of the matting. For example,
bonding DITRA-HEAT or DITRA-HEAT-DUO to
wood requires latex-modified thin-set mortar.
Additionally, all mortars (modified and unmodified)
have an acceptable temperature range that must
be observed during application and curing.
Pre-mixed thin-set mortars and mastics are not
suitable for use in conjunction with DITRA-HEAT
and DITRA-HEAT-DUO.