Installation Guide

10 HEATED FLOORS
Every substrate presents unique challenges
HEATED FLOORS
Radiant heating is one of the fastest growing market segments in the construction industry. Unlike other surface coverings, the low
thermal resistivity of ceramic and stone tiles allows them to be used in radiant heat applications without sacrificing the energy efficiency
of the system. However, there are inherent challenges in combining rigid surface coverings with radiant panel heating systems. A viable
installation system must address the magnified fluctuations in temperature that contribute to increased shear stresses between the heated
assembly and the tile covering. The system must also limit thermal striping by promoting even heat distribution and protect the assembly
from moisture, which is particularly important when gypsum concrete is used as the thermal mass.
Differential movement stresses are magnified in radiant-heated floor applications because of significant temperature
gradients. Schluter
®
-DITRA’s uncoupling function protects the ceramic or stone tile covering by neutralizing the
differential movement stresses between the heated assembly and the tile, thus eliminating the major cause of cracking
and delaminating of the tiled surface.
DITRA’s waterproofing function provides simple, effective, and permanent protection for moisture-sensitive substrates,
such as gypsum concrete and wood, used in heated floor applications.
The open rib structure of the DITRA matting allows the residual moisture in the substrate to escape. This is particularly
important for gypsum concrete since it must dry in order to gain strength. In addition, the free space beneath the matting
limits thermal striping by promoting even heat distribution throughout the assembly.
Since DITRA is virtually incompressible within the tile assembly, the advantages of uncoupling are achieved without
sacrificing point load distribution capabilities.
DITRA provides a reliable installation system that allows the integration of radiant heat and rigid surface coverings, enabling the tile
contractor to take advantage of this rapidly growing market segment.
Wood Substrate
D-RE-18
Ceramic, porcelain or stone tile
Schluter SET™, Schluter ALL-SET™,
Schluter FAST-SET™, or unmodified
thin-set mortar
DITRA or DITRA-XL
uncoupling membrane
Schluter SET™,
Schluter ALL-SET™,
Schluter FAST-SET™,
or unmodified
thin-set mortar
Electric thin-mat or wire
Schluter ALL-SET™,
Schluter FAST-SET™,
or modified thin-set mortar
Plywood or OSB
Joists, I-joists, or
trusses
Electric thin-mat or wire system
Areas of Application
over any even and structurally sound substrate
interior dry or wet areas according to heating
system manufacturer’s recommendations
Limitations
minimum 2" x 2" (50 mm x 50 mm) tile
Requirements
for wood substrates, subfloor/underlayment
configuration according to detail D-W16-T,
D-W19-T, D-W24-T, D-W24-XL-T, or D-W-S;
D-W24-XL-T for use with DITRA-XL only
for concrete substrates, see detail D-C-TS
Substrate Preparation
any leveling of the assembly must be done
prior to installing DITRA and DITRA-XL
additional preparation according to heating
system manufacturer’s directions
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 15
of this Handbook, TCNA EJ171, and TTMAC
301 MJ
Setting and Grouting Materials
modified thin-set mortar – ANSI A118.11
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, ANSI A108.9, ANSI
A108.10
heating system – follow manufacturer’s
directions
Other Considerations
install heating cable system per heating
manufacturer’s directions; encapsulate
heating cables in a skim coat of Schluter ALL-
SET™, Schluter FAST-SET™, modified thin-set
mortar or a cement-based leveling compound
and allow to cure before installing DITRA or
DITRA-XL with Schluter SET™ or unmodified
thin-set mortar
install electric thin-mat per heating
manufacturer’s directions and install DITRA
or DITRA-XL with Schluter SET™, Schluter
ALL-SET™, Schluter FAST-SET™, or
unmodified thin-set mortar
vapor barrier on crawl space floors according
to regional building codes
where a waterproof floor is required, all
DITRA and DITRA-XL seams and floor/wall
transitions must be sealed with Schluter
®
-
KERDI-BAND using Schluter SET™, Schluter
ALL-SET™, Schluter FAST-SET™, or
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
Schluter
®
-DITRA-HEAT is an uncoupling
membrane designed to secure heating
cables without encapsulating them in leveling
compounds; see schluter.com for more
information
★★★ ★★★ ★ ★★