Installation Guide

4 WOOD — Floors, Interior - Ceramic or Porcelain Tile
Every substrate presents unique challenges
WOOD
Floors, Interior - Ceramic or Porcelain Tile
D-W16-T-17
Ceramic or porcelain tile
Unmodified thin-set mortar
DITRA or DITRA-XL
uncoupling membrane
Latex p.c. mortar
Single layer of plywood
or OSB
Joists, I-joists, or
trusses
16" (406 mm) o.c. joist spacing, single layer OSB
or plywood subfloor
Areas of Application
over any even and structurally sound OSB or
plywood subfloor with 16" (406 mm) o.c.
joist spacing
interior dry or wet areas
Limitations
minimum 2" x 2" (50 mm x 50 mm) tile
for natural stone, see detail D-W-S (page 6)
and natural stone discussion (page 26)
Requirements
maximum spacing of joists, I-joists, or floor
trusses is 16" (406 mm) o.c.
minimum subfloor thickness – 19/32", 5/8"
nom. (16 mm) tongue-and-groove with 1/8"
(3 mm) gap between sheets
Substrate Preparation
verify that subfloor panels are properly
fastened to framing members
any leveling of the subfloor 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 17
of this Handbook, TCNA EJ171, and TTMAC
301 MJ
Setting and Grouting Materials
latex portland cement (p.c.) 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, A108.9, A108.10
Other Considerations
tightly butted and/or tented plywood or OSB
seams must be addressed prior to installing
DITRA and DITRA-XL
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 unmodified thin-set
mortar; see page 12
★★★ ★★★ ★ ★★
All wood materials, including OSB, plywood, and framing members, are subject to expansion, contraction, bending, and deflection as a
result of changes in moisture content and loading. Further, these deformations fluctuate over the life of the building structure.
Schluter
®
-DITRA’s uncoupling function protects the ceramic or stone tile covering from the aforementioned deformations
by neutralizing the differential movement stresses between the wood structure and the tile, thus eliminating the major
cause of cracking and delaminating of the tiled surface. Therefore, DITRA can replace a second layer of plywood in most
applications.
Since wood structures are sensitive to moisture, DITRA’s waterproofing function adds an essential element to the flooring
assembly by providing simple, effective, and permanent moisture protection.
Wood continually absorbs and releases moisture. The free space beneath the DITRA membrane allows the wood to
breathe and provides a route for any residual moisture in the wood substrate to escape.
Since DITRA 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 provides a durable installation
system for ceramic and stone tile over wood substrates.