Schluter DHERS/BW Installation Guide download pdf (Page 9)

GYPSUM — Floors, Interior - Ceramic or Stone Tile 9

Every substrate presents unique challenges

GYPSUM

Floors, Interior - Ceramic or Stone Tile

DH-G-TS-15

Gypsum concrete

Areas of Application

over gypsum concrete underlayment placed

over structurally sound wood or concrete

subﬂoors

interior dry or wet areas

Limitations

minimum 2" x 2" (50 mm x 50 mm) tile

Requirements

for wood substrates, subﬂoor/underlayment

conﬁguration according to detail DH-W16-T,

DH-W19-T, or DH-W24-T.

where radiant heat tubes are laid over the

subﬂoor, gypsum poured to a height that is

3/4" (19 mm) above the tops of the tubes is

required before installing DITRA-HEAT.

residual moisture in gypsum screed, 2.0%

(percentage by volume) or less before

installing DITRA-HEAT.

Substrate preparation

gypsum – follow manufacturer’s directions

Movement Joints

DITRA-HEAT does 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 11 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

Installation Speciﬁcations

gypsum – follow manufacturer’s directions

tile – ANSI A108.5

grout – ANSI A108.6, A108.9, A108.10

Other Considerations

since DITRA-HEAT must bond to the gypsum

concrete, follow gypsum manufacturer’s

directions regarding primers and/or special

surface preparation before installing

DITRA-HEAT.

where a waterproof ﬂoor is required, all

DITRA-HEAT seams and ﬂoor/wall transitions

must be sealed with KERDI-BAND using

unmodiﬁed thin-set mortar; see page 10.

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.

vapor barrier on crawl space ﬂoors according

to regional building codes.

Bonding ceramic or stone tiles directly to gypsum concrete substrates is generally considered questionable or not recommended. The

challenges associated with gypsum-based underlayments include the requirement of an extended drying period before installing tile and

continued sensitivity to the reintroduction of moisture throughout the life of the installation. In addition, since the coefﬁcient of thermal

expansion of gypsum concrete is substantially greater than that of ceramic tile, shear stresses caused by temperature ﬂuctuations can

result in delamination or cracking of the tile covering. This is particularly important when gypsum concrete is used as a thermal mass for

radiant heated ﬂoors. With the increasing popularity of radiant heated ﬂoors, which typically utilize gypsum concrete, tile installers need a

reliable installation system to address these issues.

DITRA-HEAT’s uncoupling function protects the ceramic or stone tile covering by neutralizing the differential movement

stresses between the gypsum concrete substrate and the tile, thus eliminating the major cause of cracking and delaminating

of the tiled surface.

DITRA-HEAT’s waterprooﬁng function prevents the reintroduction of moisture to gypsum concrete underlayments, which, if

not prevented, could signiﬁcantly compromise performance of the underlayment and lead to damage of the tiled surface.

The conﬁguration of the DITRA-HEAT matting provides free space to accommodate vapor emissions from the gypsum.

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, lightweight construction methods, DITRA-HEAT provides a durable

installation system for ceramic and stone tile over gypsum 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.

DITRA-HEAT is useful even in applications where hydronic radiant-heating tubes are incorporated in gypsum concrete, as there may be

times when ﬂoor warming is desirable while radiant heating is not necessary.

Ceramic or stone tile

Unmodiﬁed thin-set mortar

DITRA-HEAT

uncoupling membrane

and heating cables

Unmodiﬁed

thin-set mortar

Gypsum

concrete

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