Use and Care Guide

thus eliminating the major cause of cracking
and delaminating of the tiled surface. This
is particularly important since these stresses
are magnified by the significant temperature
gradients common in exterior applications.
DITRA and DITRA-XL provides effective
waterproofing that will protect the tile
assembly from the recurring introduction
of water which is common in exterior
applications.
The free space beneath the
DITRA and
DITRA-XL matting provides a route for any
residual moisture in the substrate to escape.
This is especially important when installing tile
over a young slab, a concrete slab subject
to moisture migration, or a fresh mortar bed.
Since DITRA and DITRA-XL is virtually
incompressible within the tile assembly,
the advantages of uncoupling are achieved
without sacrificing point load distribution
capabilities.
Installation
For complete installation guidelines and
warranty criteria, please contact Schluter
®
-
Systems at 800-472-4588 (USA) or 800-
667-8746 (Canada) or by e-mail at info@
schluter.com to receive a copy of the
Schluter
®
-DITRA Installation Handbook and a
step-by-step installation video. To download
a PDF version of the Handbook or to view
the installation video online, please visit www.
schluter.com.
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, etc. 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 with
unmodified thin-set mortar?
Answer: YES. In fact, we recommend it.
Here’s why: Portland cement-based
unmodified thin-set mortars are dependent
on the presence of moisture for hydration
in order to gain strength. Since DITRA is
impervious, it does 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 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 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,
and whether the installation is interior or
exterior]. Therefore, extended cure times
could be required before grouting if using
modified thin-set mortars between DITRA
and ceramic tile, including porcelain tile. If
extended cure times were not observed,
the results could be unpredictable. This is
even more important to consider in exterior
applications that are exposed to rain as there
is the additional concern of latex leaching.
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, etc. 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 or
DITRA-XL 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 and DITRA-
XL 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.
Movement Joints
DITRA and DITRA-XL do not eliminate the
need for movement joints, including perimeter
joints, within the tiled surface. Please refer to
the Schluter
®
-DITRA Installation Handbook
for movement joint placement guidelines.
UNCOUPLING MEMBRANES
4