Installation Guide

8 CONCRETE — Floors, Interior - Ceramic or Stone Tile
Every substrate presents unique challenges
CONCRETE
Floors, Interior - Ceramic or Stone Tile
DH-C-TS-20
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.
The uncoupling function of DITRA-HEAT 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.
The DITRA-HEAT membrane’s waterproofing ability not only protects the substrate from harmful substances, it also slows the drying
of fresh concrete, which reduces the chances of cracking and curling of the slab.
The configuration of the DITRA-HEAT matting provides free space to accommodate vapor emissions from the concrete slab. This
allows the installation of DITRA-HEAT 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-HEAT is virtually incompressible within the tile assembly, the advantages of uncoupling are achieved without sacrificing
point load distribution capabilities.
By addressing all of the challenges associated with today’s fast construction methods, DITRA-HEAT provides a durable installation system for
ceramic and stone tile over concrete substrates.
DITRA-HEAT combines the flexibility of loose heating cables with the ease of installation of mat systems. Cables can be placed wherever heat is
desired, without creating height differences in the floor. Self-leveling compounds are not required to encapsulate the cables, significantly reducing
installation time and effort compared to uncoupling membranes over other electric floor warming systems. Concrete substrates can absorb heat
energy increasing the time it takes for floors to warm up, particularly when there is no insulation layer below the concrete. In some cases, floors
may never reach the desired temperature. DITRA-HEAT-DUO features an integrated thermal break to reduce sound transmission through floor-
ceiling assemblies, reduce heat loss to concrete substrates, and improve floor warming response times.
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-HEAT and
DITRA-HEAT-DUO sealed with 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-HEAT or
DITRA-HEAT-DUO, 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-HEAT or DITRA-HEAT-
DUO and tile can begin as soon as the slab can
be walked upon
slab to be free of standing water
sound control floors - Schluter perimeter
movement joints recommended to help limit
sound energy transfer
Substrate Preparation
any leveling of the subfloor must be done prior
to installing DITRA-HEAT and DITRA-HEAT-
DUO
Movement Joints
DITRA-HEAT and DITRA-HEAT-DUO 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 13 of this
Handbook, TCNA EJ171, and TTMAC 301 MJ
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-HEAT and DITRA-HEAT-DUO seams
and floor/wall transitions must be sealed with
KERDI-BAND using unmodified thin-set mortar;
see page 12.
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
consider the use of DITRA-HEAT-DUO to
improve the response time of DITRA-HEAT in
applications over concrete. See page 31 for
more information.
Ceramic, porcelain
or stone tile
Schluter SET
®
, Schluter ALL-SET
®
,
Schluter FAST-SET
®
, or unmodified
thin-set mortar
DITRA-HEAT
or DITRA-HEAT-DUO
uncoupling membrane
and heating cables
Schluter SET
®
,
Schluter ALL-SET
®
,
Schluter FAST-SET
®
,
or unmodified thin-set mortar
Concrete