Installation Guide

10 CONCRETE — Floors, Interior - Ceramic or Stone Tile
Every substrate presents unique challenges
CONCRETE
Floors, Interior - Ceramic or Stone Tile
D-C-TS-15
Ceramic or stone tile
Unmodified thin-set mortar
DITRA or DITRA-XL
uncoupling membrane
Unmodified
thin-set mortar
Concrete
There are various challenges associated with the installation of hard surface coverings on concrete substrates.
To begin, the coefficient of thermal expansion of concrete is close to twice that of ceramic tile. Additionally, tile contractors are often expected
to install tile over young concrete (concrete cured less than 28 days). However, rigid surface coverings installed over young concrete are
susceptible to damage as a result of shrinkage during curing. Pre-stressed/post-tensioned concrete slabs are also commonplace in today’s
construction environment. Although pre-stressing is used to help control deflections in concrete structures, these slabs are still subject to
deformations caused by changes in moisture, temperature, and loading. Many concrete slabs on or below grade are subject to moisture
migration, which can be problematic. Furthermore, these structures experience the same deformations as stated above.
Schluter
®
-DITRA’s uncoupling function protects the ceramic or stone tile covering by neutralizing the differential
movement stresses between the concrete substrate and the tile, thus eliminating the major cause of cracking and
delaminating of the tiled surface.
DITRA’s waterproofing ability not only protects the substrate from moisture and harmful substances, it also slows the
drying of fresh concrete, which reduces the chances of cracking and curling of the slab.
The free space beneath the DITRA matting provides a route for any residual moisture in the concrete slab to escape. This
allows the installation of DITRA and the tile covering as soon as the slab can be walked upon. Vapor management is also
essential for slabs subject to moisture migration.
Since DITRA is virtually incompressible within the tile assembly, the advantages of uncoupling are achieved without sacrificing
point load distribution capabilities. This allows DITRA to be installed in commercial and industrial applications exposed to
heavy vehicular traffic, provided the type, format, and thickness of the tile is appropriate for the application.
By addressing all of the challenges associated with today’s fast construction methods, DITRA provides a durable installation system for
ceramic and stone tile over concrete substrates.
Concrete subfloor
Areas of Application
over any structurally sound and even
concrete subfloor
young concrete (concrete cured less than 28 days)
on or below grade concrete subject to
moisture migration
post-tensioned or pre-stressed concrete
cracked concrete
Limitations
minimum 2" x 2" (50 mm x 50 mm) tile
concrete slabs subject to moisture migration
must have all seams in DITRA and DITRA-XL
sealed with Schluter
®
-KERDI-BAND using
unmodified thin-set mortar
any cracks in concrete subfloor must exhibit
in-plane movement only; thin-set tile
assemblies, including those incorporating
DITRA or DITRA-XL, cannot accommodate
differential vertical displacement
Requirements
slab to be structurally sound
slab to be free of waxy or oily films and curing
compounds (when present, mechanical
scarifying is necessary)
the installation of DITRA or DITRA-XL and tile
can begin as soon as the slab can be walked
upon
Substrate Preparation
any leveling or sloping of the slab or
assembly must be done prior to installing
DITRA and DITRA-XL
Movement Joints
DITRA and DITRA-XL do not eliminate the
need for movement joints, including perimeter
joints, within the tiled surface. Movement
joints must be installed in accordance with
industry standards and norms; see page 18
of this Handbook, TCNA EJ171, and TTMAC
301 MJ
concrete floors may incorporate various
movement joints; see page 19 of this
Handbook for guidelines on how to treat the
different types of joints (control/contraction
joints, expansion joints, etc.)
Setting and Grouting Materials
unmodified thin-set mortar – ANSI A118.1
grout – ANSI A118.3, A118.6, A118.7, A118.8
Setting and Grouting Specifications
tile – ANSI A108.5
grout – ANSI A108.6, A108.9, A108.10
Other Considerations
where a waterproof floor is required, all
DITRA and DITRA-XL seams and floor/wall
transitions must be sealed with Schluter
®
-
KERDI-BAND using unmodified thin-set
mortar; see page 14
certain moisture-sensitive stones, e.g., green
marble, or resin-backed tiles may require special
setting materials. Consult stone supplier and
Schluter-Systems for more information
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