Specification

Applications Floor A. Durock cement board should be cut to size with a knife and straight edge. A power saw should be used only if it is
equipped with a dust-collection device. Installer should wear NIOSH/MSHA-approved dust mask.
B. Laminate
Durock cement board to subfloor using Type 1 organic adhesive, latex-fortified mortar or dry-set
mortar mixed with acrylic latex additive that is suitable for bonding cement backer board to plywood subfloor,
with 1/4" square-notched trowel for mortar, 5/32" V-notched trowel for adhesive. Place cement board with joints
staggered from subfloor joints. Fit ends and edges closely, but not forced together, leaving a 1/8" gap. Fasten to
subfloor with 1-1/4"
Durock™ tile backer screws for wood framing or 1-1/2" hot-dipped galvanized roofing nails
spaced 8" o.c. in both directions, with perimeter fasteners at least 3/8" and less than 5/8" from ends and edges.
Drive nails and screws so that bottoms of heads are flush with panel surface to ensure firm panel contact with sub-
floor. Do not overdrive fasteners.
Countertop Fasten minimum 3/4" plywood or OSB across cabinet supports. Position ends and edges over supports.
Staple film over the plywood base. Fasten
Durock panels to plywood with 1-1/4" Durock wood screws or 1-1/2"
galvanized roofing nails spaced 8" o.c. in both directions and around edges. Fit ends and edges closely, but not
forced together.
Joint Treatment Prefill joints with tile-setting mortar or adhesive and then immediately embed Durock
™
tile backer tape and
level joints.
Limitations 1. 1/4"
Durock cement board products are only for interior construction applied to minimum 5/8" exterior-grade
plywood or OSB.
2. Maximum framing spacing: 24" o.c. Maximum fastener spacing: 8" o.c.
3. Maximum design deflection: L/360 of the span. Some finish materials may require a more rigid sub-assembly
(such as large format tile and natural stone products). In these cases, follow the manufacturer’s minimum
requirements.
4. 1/4"
Durock cement board should not be used for wall or ceiling applications. For wall or ceiling applications,
use 1/2" or 5/8"
Durock cement board.
Technical Data Property ASTM Test 1/4"
Reference Value
Flexural strength—psi C947 1000
Indention strength—psi D2394 >1250
Water absorption—% by weight 24 hours C473 15
Weight-psf C473 <1.9
Freeze/thaw resistance—procedure B, number of cycles with no deterioration C666 100
Non-combustibility E136 Pass
Surface burning characteristics—flame/smoke E84 0/0
Standard method for evaluating ceramic floor tile installation systems C627 Light Commercial
Manufactured by
United States Gypsum Company
550 West Adams Street
Chicago, IL 60661
800 USG.4YOU (874-4968)
usg.com
CB250/rev. 4-11
© 2011, United States Gypsum Company
Printed in U.S.A.
medical advice. Inhalation of
dust may be corrosive or cause
chemical burns or irritation to
nose, throat and respiratory
tract. Avoid breathing dust. Use
in a well-ventilated area or pro-
vide sufficient local ventilation.
If dusty, wear a NIOSH/MSHA-
approved dust respirator.
Wash thoroughly with soap and
water after use. Do not ingest.
If ingested, call physician. If
cutting board with a power tool,
use a wet or vacuum saw to
reduce the amount of dust gen-
erated. Panels are heavy and
can fall over, causing serious
injury or death. Avoid creating
a tripping hazard and do not
exceed floor limit loads. Long-
term breathing of respirable
crystalline silica dust can cause
permanent lung damage and/or
cancer. Product safety informa-
tion: 800 507-8899
or usg.com.
KEEP OUT OF REACH
OF CHILDREN.
Trademarks
The following trademarks are
owned by United States Gypsum
Company or its related
companies:
Durock, USG, USG
in stylized letters.
Note
Products described here
may not be available in all
geographic markets. Consult
your United States Gypsum
Company sales office or
representative for information.
Notice
We shall not be liable for inci-
dental and consequential dam-
ages, directly or indirectly sus-
tained, nor for any loss caused
by application of these goods
not in accordance with current
printed instructions or for other
than the intended use. Our
liability is expressly limited to
replacement of defective goods.
Any claim shall be deemed
waived unless made in writing
to us within thirty (30) days from
date it was or reasonably should
have been discovered.
Safety First!
Follow good safety/industrial
hygiene practices during
installation. Wear appropriate
personal protective equipment.
Read MSDS and literature
before specification and
installation.
Product Information
See usg.com for the most up-
to-date product information.
Warning
Portland cement is strongly
alkaline. Direct contact can be
corrosive and cause severe
damage or chemical burns
to the eyes and wet or moist
skin. Avoid contact with eyes
and skin. Wear eye protec-
tion, alkali-resistant protective
gloves, long-sleeved shirts and
pants to prevent direct contact.
If eye contact occurs, imme-
diately flush thoroughly with
water for 30 minutes and seek