SA932 09305
Durock
®
systems
cement board
DUROCK
®
DUROCK cement board offers architects, builders and tile contractors a strong, water-durable tile base for
Cement Board
tub and shower areas. Also an ideal underlayment for tile on floors and countertops in new construction and
remodeling. Board is readily applied over wood or steel framing spaced 16" o.c. with corrosion-resistant wood or
steel screws or hot-dipped galvanized roofing nails. After joints are treated, ceramic wall or floor tile is applied
using latex-fortified mortar or Type I organic adhesive.
DUROCK cement board is preferred by many applicators as a base for directly applied finishes, tile, stone and
thin-brick used in building exteriors.
DUROCK
™
Corrosion-resistant; 8-gauge; wafer heads with countersinking ribs to prevent strip-out; self-drilling points. DUROCK
Tile Backer Screws
tile backer screws for wood framing come in three lengths: 1-1/4", 1-5/8" and 2-1/4".
DUROCK tile backer screws
for steel framing can be used with steel framing where steel thickness is from 14 to 20-gauge; they come in two
lengths: 1-1/4" and 1-5/8". Both wood and steel screws have heads a minimum of 0.40" in diameter; their driving
recess is a No. 2 “Phillips” design.
DUROCK
™
Alkali-resistant glass-fiber tape reinforces joints to provide a strong, continuous surface. Each roll 2" x 50',
Tile Backer Tape
2" x 150', 2" x 250' or 4" x 150'.
Features and
Dual Surface Although both sides of DUROCK cement board are suitable for either mastic or thin-set mortar applications,
Benefits of the following is offered as a guide:
DUROCK – Smooth side for mastic applications; increases adhesive coverage
Cement Board
– Textured surface enhances bonding, reduces tile slip with mortar applications
Dimensional – Low thermal and hygrometric expansion helps prevent cracking
Stability
– Will not swell, soften, decay, delaminate or disintegrate in water
Fire-Resistance – Noncombustible panel
– Assemblies with 1/2"
DUROCK cement board have achieved 1- and 2-hour fire-resistance ratings
Light Weight – At approximately 2.4 psf, the 1/2" thick board is approximately 25% lighter than other cement boards
Easy Installation – Easy to cut and fasten
– Installs up to 20% faster than other cement boards
Convenient Sizes – May be ordered in sizes to meet job requirements (see table of sizes and packaging)
Versatility – Provides a smooth, sound base for glass and ceramic mosaics; ceramic and quarry tile; lugged tile; thin
stone tile; and thin brick
– Adaptable for fences, fireplace fronts, mobile home skirting, agricultural buildings, garage wainscoting
and various exterior synthetic stucco systems.
Limitations 1. Designed for positive or negative uniform loads up to 60 psf. For complete information on the use of
DUROCK
panels in exterior systems, consult uniform load table on page 3 for applicable positive or negative uniform loads
on wall systems.
2. Wall applications: Maximum stud spacing: 16" o.c. (24" o.c. for cavity shaft wall assembly). Framing shall be
designed (based on stud properties alone) not to exceed L/360 deflection for tile and thin brick, L/240 for
direct-applied exterior finish systems. Maximum fastener spacing: 8" o.c. for wood and steel framing; 6" o.c.
for ceiling applications.
3. Floor applications: Maximum joist spacing 24" o.c. The subfloor system should be designed with a minimum
deflection limit of L/360 for 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.
The subfloor should be APA Span-Rated Plywood or OSB with an Exposure 1 classification or better with tongue
and groove or back blocked at the unsupported edges.
4. Maximum dead load for ceiling system is 7.5 psf.
5. Steel framing must be 20-gauge equivalent or heavier.
6. Do not use drywall screws or drywall nails. Do not use drywall joint tape.
7. Do not use 1/4"
DUROCK cement board for wall or ceiling applications.
8. Do not use
DUROCK cement board with vinyl flooring.
9.
DUROCK cement board is not designed for use as a structural panel.
DUROCK
®
Brand
Cement Board Systems
United States Gypsum Company SA932 2
DUROCK
Cement Board Systems
United States Gypsum Company SA932 3
Product Data Material – Formed in a continuous process of aggregated portland cement slurry with polymer-coated, glass-fiber
mesh completely encompassing edges and back and front surfaces.
Edges – Formed smooth.
Ends – Square cut.
Sizes and Packaging
Type Size (thickness x width x length)
1
Units (pcs)
2
Cement Board 1/2" x 32" x 5' 50
1/2" x 36" x 5' 50
1/2" x 32" x 8' 30
1/2" x 48" x 8' 30
5/8" x 36" x 5' 30
5/8" x 48" x 8' 24
1/4" x 36" x 5' 60
1. Other lengths available. Contact your USG Representative. 2. Shipped in packaging units as shown.
Technical Data
Uniform Load —
1/2"
DUROCK
Cement Board
Standards
DUROCK cement board exceeds the ANSI Standards for cementitious backer units (CBU). See ANSI A1
18.9 for Test Methods and Specifications for CBU and ANSI A108.11 for Interior Installation of CBU.
All
DUROCK cement board products meet ASTM Standard E136 for noncombustibility. Exceeds ASTM C1325
standards for non-asbestos fiber-mat reinforced cementitious backer units.
L
U
®
09305/UNI
BuyLine 3900
Stud Spacing Fastener Spacing Design Wind Load (I/240) Design Wind Load (I/360)
12" o.c. 8" o.c. 45 psf 45 psf
6" o.c. 60 psf 60 psf
16" o.c. 8" o.c. 33 psf 30 psf
6" o.c. 45 psf 30 psf
24" o.c.
(for shaft wall
assemblies only)
8" o.c. 13 psf 9 psf
6" o.c. 13 psf 9 psf
Property Unit of Measure ASTM Test
Method
5/8" DUROCK
Cement Board
1/2"
Cement Board
1/4"
Underlayment
Flexural strength psi C947 > 480 > 750 > 1000
Indentation strength psi D2394 > 1250 > 1250 > 1250
Shear bond strength psi ANSI A118.4 > 50 > 50 > 50
Water absorption % by wt. 24 hrs. C473 15 15 15
Nail-pull resistance lb. (0.4" head
diameter, wet or dry)
C473 > 90 > 90 —
Weight psf C473 3 2.4 < 1.9
Freeze/thaw resistance procedure B, number of
cycles with no deterioration
C666 100 100 100
Mold resistance — G21 No growth No growth No growth
Noncombustibility Pass/Fail E136 Pass Pass Pass
Surface burning characteristics flame/smoke E84 0/0 0/0 0/0
Thermal “R”/k value C518 .49/1.27 0.39/1.27 —
Standard method for
evaluating ceramic floor
tile installation systems
Passes cycles 1-6 C627 Light
commercial
Light
commercial
Light
commercial
Minimum bending radius ft. (requires special framing
details available upon request)
—
6 6 —
1-Hour Fire-Rated Construction Steel Truss Acoustical Performance
Construction Detail Description Test Number STC ITC Test Number
• 5/8" SHEETROCK FIRECODE C Core gypsum panels
– RC-1 channels or equivalent
– joints finished
– steel roof deck
– steel truss 48" o.c.
• roof covering and roof insulation over 1/2" DUROCK cement
board or 1/2" SHEETROCK
®
gypsum panels
UL Des P521, P525,
527, 529
1-Hour Fire-Rated Construction Non-Loadbearing, Steel Framed Acoustical Performance
Construction Detail Description Test Number STC Test Number
4
5
⁄8"
• 1/2" DUROCK cement board
– 3-1/2" 20 gauge steel studs 16" o.c
– 3" ROXUL mineral wool AFB
• 5/8" SHEETROCK
®
brand FIRECODE
®
Core gypsum panels,
one side
U433
2-Hour Fire-Rated Construction Non-Loadbearing, Steel Framed Acoustical Performance
Construction Detail Description Test Number STC Test Number
6
1
⁄8"
• 1/2" DUROCK cement board and 1/4" ceramic tile
• base layer 1/2" SHEETROCK
®
brand FIRECODE
®
C Core
gypsum panels
– 3-5/8" 20-gauge steel studs 16" o.c.
– 3" THERMAFIBER SAFB
– face layer joints taped
• alternate design 2 layers 1/2" SHEETROCK FIRECODE C Core
gypsum panels, one side
U443
56 SA-851016
Based on alternate Design
58
SA-851028
1-Hour Fire-Rated Construction Chase Walls, Steel Framed Acoustical Performance
Construction Detail Description Test Number STC Test Number
5
1
⁄4"
• face layer 1/2" DUROCK cement board
• base layer 5/8" SHEETROCK FIRECODE Core gypsum panels or
sheathing, or FIBEROCK
®
brand panels
– 3-1/2" 20-gauge struc studs 16" o.c.
– 3" mineral wool batt
• 5/8" SHEETROCK FIRECODE Core opposite side
UL Des U473
1-Hour Fire-Rated Construction Loadbearing, Wood Framed Acoustical Performance
Construction Detail Description Test Number STC Test Number
5"
• 1/2" DUROCK cement board and 1/4" ceramic tile
– 2 x 4 wood studs 16" o.c.
– 3-1/2" THERMAFIBER SAFB
– joints taped
• alternate design 5/8" SHEETROCK FIRECODE Core gypsum panels,
one side
UL Des U329
37
USG-840404
40
USG-830314
5
1
⁄8"
• 1/2" DUROCK cement board
– base layer 15/32" plywood
– 2 x 4 wood studs 16" o.c.
– 3" THERMAFIBER SAFB
– joints taped and treated
• 5/8" SHEETROCK FIRECODE Core gypsum panels, other side
U303
2-Hour Fire-Rated Construction Chase Walls, Steel Framed Acoustical Performance
Construction Detail Description Test Number STC Test Number
9"
• 1/2" DUROCK cement board and 1/4" ceramic tile
– Two rows 2 x 4 16" o.c. on 2 x 8 common plate
– 3-1/2" THERMAFIBER SAFB both cavities
– joints taped
– load-bearing up to 50% allowable design load
WHI-495-0505
and 0508
50
SA-840523
DUROCK
Cement Board Systems
United States Gypsum Company SA932 4
Partitions
Roof / Ceilings
2-Hour Fire-Rated Construction Dimensional Lumber, Wood Framed Acoustical Performance
Construction Detail Description Test Number STC ITC Test Number
13
1
⁄4"
• Two layers 5/8" SHEETROCK FIRECODE C Core gypsum panels
– 8" x 8" ceramic tile
• 1/2" DUROCK cement board
• 1" SHEETROCK
®
gypsum liner panels
– 1/2" plywood
– 2 x 10 wood joist 16" o.c.
– 3" mineral wool batt
– RC-1 channel or equivalent
UL Des L541
52 RAL-IN-89-5
58 RAL-TL-89-145
51 RAL-IN-89-7
59 RAL-TL-89-146
Based on carpet/pad over oriented strand
board in place of ceramic tile and cement
board
60 RAL-TL-89-141
62 RAL-IN-89-8
2-Hour Fire-Rated Construction Steel Framed, Non-Loadbearing Acoustical Performance
Construction Detail Description Test Number STC ITC Test Number
5
5
⁄8"
• 1/2" DUROCK cement board
• base layer 1/2" SHEETROCK
®
MOLD TOUGH
®
FIRECODE
®
C Core
gypsum panels, both sides
– 3-5/8" 20-gauge minimum steel studs 16" o.c.
– 3" THERMAFIBER SAFB
• alternate design, double-layer 1/2" SHEETROCK FIRECODE
C Core gypsum panels, interior
UL Des U474
1-Hour Fire-Rated Construction Steel Framed, Non-Loadbearing Acoustical Performance
Construction Detail Description Test Number STC ITC Test Number
5
1
⁄4"
• 1/2" DUROCK cement board
• base layer 5/8" SHEETROCK MOLD TOUGH FIRECODE Core
gypsum panels
– 3-1/2" 20 gauge steel load-bearing studs 16" o.c.
– 3" THERMAFIBER SAFB
• 5/8" SHEETROCK FIRECODE Core gypsum panels, interior side
UL Des U473
1-Hour Fire-Rated Construction Wood Framed, Loadbearing Acoustical Performance
Construction Detail Description Test Number STC ITC Test Number
5
1
⁄8"
5
1
⁄4"
• 1/2" DUROCK cement board, interior side
– 15/32" plywood
– 2 x 4 wood studs 16" o.c.
– 3" THERMAFIBER SAFB
– joints finished
• 5/8" SHEETROCK FIRECODE Core gypsum panels or
SECUROCK
®
glass-mat sheathing panels, other side
UL Des U303
1-Hour Fire-Rated Construction Wood Framed, Loadbearing Acoustical Performance
Construction Detail Description Test Number STC ITC Test Number
5"
• 1/2" DUROCK cement board and 1/4" ceramic tile exterior
– 2 x 4 wood studs 16" o.c.
– 3-1/2" THERMAFIBER SAFB
• 5/8" SHEETROCK FIRECODE Core gypsum panels
– optional veneer plaster
UL Des U329
DUROCK
Cement Board Systems
United States Gypsum Company SA932 5
Notes: DUROCK cement board, 5/8" thick, may be substituted for 1/2" cement board panels in all assemblies listed above. FIBEROCK
®
abuse-resistant gypsum fiber panels, 5/8" thick, may be substituted for 1/2" SHEETROCK FIRECODE C Core
gypsum panels, or 5/8" SHEETROCK FIRECODE Core gypsum panels, in all assemblies listed above. Where thermal insulation is shown in assembly drawing, the specific product is required in the assembly to achieve the stated fire rating.
Fiberglass insulation cannot be substituted for THERMAFIBER insulation. Where the wall is exposed to moisture, use a moisture-resistant barrier behind the cement board.
1. Steel framing must be 20 gauge or heavier.
2. Estimate based on 25-gauge steel studs.
Floor / Ceilings
Exterior Walls
DUROCK
Cement Board Systems
United States Gypsum Company SA932 6
tile
3
⁄
4
" min. plywood
D
UROCK
cement
board or underlayment
D
UROCK
tile
backer tape
liquid or sheet membrane
Type 1 organic adhesive or
latex-fortified mortar
padding
wood or steel joists
carpet
3
⁄
4
" min. plywood or OSB subfloor
Note: For bonding cement backerboard to plywood subfloor, use Type 1 organic adhesive or
latex-fortified mortar that is suitable for this kind of application. For application of various types of
tiles to cement backerboard on floors or countertops, contact the tile manufacturer for the
appropriate type of tile-setting mortar.
tile
D
UROCK
cement board
or underlayment
Type 1 organic adhesive or
latex-fortified mortar
Countertops Floors, interior—wood or steel joists
hanger
20 ga. min. metal
furring channel
D
UROCK
fastener 6" o.c.
control joint
D
UROCK
cement panel
ceramic tile
wire tie
20 ga. min. metal
furring channel
hangerwire tie
1
1
/2" channel
2
3
/4"
DUROCK tile
backer screw
6" o.c.
wood
blocking
16" o.c.
D
UROCK
tile
backer tape
1
/
2
" D
UROCK
cement panel
2"x4" wood
stud 16" o.c.
ceramic tile
1
/
2
" S
HEETROCK
gypsum panel
D
UROCK
tile backer
screws for wood
framing 6" o.c.
Type I organic adhesive
or latex-fortified mortar
Type 1 organic
adhesive or
latex-fortified mortar
D
UROCK
tile
backer tape
D
UROCK
cement panel must be
primed before application of
joint compound or use it on one
side only and set the tile side
with mastic.
see note
above*
*
Wood soffit framingSuspended ceiling detail
Tub and shower—single layer board
DUROCK Brand
cement panel
tile
wood or metal studs
Type I organic adhesive
or latex-fortified mortar
1" to 1
3
⁄
4
" rein-
forced mortar bed
shower pan or membrane
sloped fill weep holes
crushed tile or stone
sealant
1/4" gap
X
D
UROCK
cement panel
caulk
tub rim
leveling guide
1/4" gap
Type 1 organic
adhesive or latex-
fortified mortar
X
DUROCK cement panel
Type 1 organic adhesive
or latex-fortified mortar
tile
caulk
1/4" gap
horizontal support
at DUROCK
panel edge
precast concrete shower base
X
DUROCK tile backer
screw for steel
or wood framing
8" o.c.
tile
Type 1 organic
adhesive or latex-
fortified mortar
DUROCK tile
backer tape
D
UROCK
cement panel
setting material
wood or steel studs
16" o.c. max.
membrane
(if required)
Walls, interior and exterior—wood or steel studs
DUROCK
Cement Board Systems
United States Gypsum Company SA932 7
D
UROCK
tile backer tape
4" D
UROC
k tile backer tape embedded
in exterior basecoat
water barrier
D
UROCK
tile backer
screws
at 8" o.c.
exterior
finish
in tile areas treat D
UROCK
joints by
embedding 2" D
UROCK
tile backer
tape in tile setting material
wood or
metal
studs at
16" o.c.
D
UROCK
panel
2" D
UROCK
tile backer tape
Type 1 organic
adhesive or
latex-fortified
mortar
exterior
basecoat
D
UROCK
panel
tile setting
mortar
tile base
pool
Typical bathtub installation
Typical swimming pool installation (tile or exterior finish)
DUROCK alkali-resistant tape
DUROCK tile backer screws for wood framing
DUROCK tile backer screws for steel framing
3
/8" TYPE S-12
pan head screw
steel runner
steel framing
member—gauge
and size as required
3
/
8
" TYPE S-12
pan head screw
steel framing
members—misc.
gauge and depth
Fixture attachment — steel framing
Hot-dipped galvanized roofing nails
Good Design 1. System Performance Systems covered herein have been tested and evaluated for use as described. For other system applications,
Practices
consult your local representative.
All details, specifications and data contained in this literature are intended as a general guide for using
DUROCK cement board systems. These products must not be used in a design or construction of any given
structure without complete and detailed evaluation by a qualified structural engineer or architect to verify
suitability of a particular product for use in the structure.
Information in this publication should be used only for
DUROCK cement board systems, as physical properties of
competitive products may vary. United States Gypsum Company assumes no liability for failure resulting from the use
of alternative materials or improper application or installation of
DUROCK cement board systems as specified herein.
United States Gypsum Company will provide building officials and design professionals upon written request with
test certification for published fire, sound and structural data covering systems constructed with Company products
and assembled to meet performance requirements of established test procedures specified by various agencies.
2. Expansion and Contraction Wall surfaces should be isolated with surface control joints (sometimes referred to by the industry as expansion
joints) or other means where: (a) a wall abuts a structural element or dissimilar wall or ceiling; (b) construction
changes within the plane of the wall; (c) tile and thin brick surfaces exceed 16'. Surface control joint width should
comply with architectural practices.
Location of building control joints is the responsibility of the design professional/architect. Steel framing at
building control joints that extend through the wall (with top and bottom runner tracks broken) should have 1-1/2"
cold-rolled channel alignment stabilizers spaced a maximum of 5' o.c. vertically. Channels should be placed
through holes in the stud web of the first two adjacent studs on both sides of the joint and securely attached to
the first adjacent stud on either side of the joint.
Cement board should be separated at all surface and building control joints. Where vertical and horizontal joints
intersect, the vertical joint should be continuous and the horizontal joint should abut it. Splices, terminals and
intersections should be caulked with a sealant complying with architectural practices and sealant manufacturer
recommendations. Do not apply tile or finishes over caulked sealed expansion joints.
3. Water Management DUROCK cement board is vapor permeable and does not deteriorate in the presence of water. For interior
applications, if a vapor retarder or waterproof construction is specified, a separate barrier must be applied
over or behind the
DUROCK cement board. If waterproofing is desired, use DUROCK tile membrane. See USG
literature piece CB492 for
DUROCK tile membrane product information.
4. Swimming Pool Enclosures DUROCK cement board systems may be used for the walls and ceilings around indoor swimming pools.
Consideration shall be given to adequate ventilation in plenums and corrosion protection of metal hangers and
framing members.
5. Soffits and Ceilings DUROCK cement board systems finished with ceramic tile, thin brick and textured finish may be used on properly
vented soffits and ceilings with
DUROCK tile backer screws spaced 6" o.c. max. A qualified structural engineer
should evaluate design including uplift bracing.
6. Steam Rooms and Saunas For steam rooms and saunas where temperatures exceed 120 °F for extended periods, use latex-fortified portland
cement mortar; do not use organic adhesive.
7. Abuse Resistant Partitions IMPERIAL
®
brand finish plaster and DIAMOND
®
interior finish plaster can be applied over DUROCK cement board to
provide a high-impact resistant wall. See United States Gypsum Company publication SA920 for specifications.
8. Window and Door Openings All windows, door openings and termination points must be properly flashed and caulked.
9. Smooth Side/Rough Side DUROCK cement board has a smooth side and a rough side. Although both sides of DUROCK cement board are
suitable for either mastic or thin-set mortar applications, as a general guide, use the smooth side for mastic
applications and the
rough side for mortar applications.
10. Shadowing and Spotting When the outside temperature differs considerably from the building's interior temperature, airborne dirt can
accumulate on the colder regions of walls, causing “shadowing” or “spotting,” particularly over fasteners and
framing. This is a natural phenomenon that occurs through no fault in the products.
Where temperature, humidity and soiling conditions are expected to cause objectionable blemishes, provide
a thermal separation between the interior and exterior faces.
DUROCK
Cement Board Systems
United States Gypsum Company SA932 8
11. Leaching and Latex leaching and efflorescence are natural phenomena that occur with the use of latex modified mortars and
Efflorescence
grouts through no fault in the products. To help protect against their occurrence, follow current industry
guidelines and recommendations. If efflorescence is present, use a stiff nylon brush to remove any loose material.
12. Panel Micro-Cracking DUROCK cement board is formulated to develop fine micro-cracking (also called multiple-cracking) in the panel.
The micro-cracking process helps to evenly relieve the stored strain energy in the product due to handling and
installation, external loads, and/or panel restrained movement. The presence of micro-cracks in the panel should
not be considered a product defect.
13. Vapor Retarders Humidity and temperature conditions may require a vapor retarder. Its location should be determined by a
qualified mechanical engineer or architect to prevent moisture condensation within the wall.
14. Corrosion Protection All architectural components, such as anodized-aluminum window frames, trims, flashings and casings, shall be
protected from alkaline building materials such as cement board, portland cement basecoats, mortars and grouts.
Specifications
1.1 Specify to meet project requirements.
Part 1:
Scope
General
1.2 All materials, unless otherwise indicated, shall be manufactured by United States Gypsum Company and shall be
Qualifications
installed in accordance with its current printed directions.
1.3 All materials should be delivered and stored in their original unopened package and stored in an enclosed shelter
Delivery and
providing protection from damage and exposure to the elements. Even though the stability and durability of DUROCK
Storage of Materials
cement board is unaffected by the elements, moisture and temperature variations may have an effect on the
bonding effectiveness of basecoats and adhesives. Store all
DUROCK cement board panels flat.
1.4
In cold weather and during DUROCK cement panel and tile installation, temperatures within the building shall
Environmental Conditions
be maintained within the range of 40 to 100 °F. Adequate ventilation shall be provided to carry off excess moisture.
Interior Applications Wood framing shall approximate the moisture content it will reach in service by allowing the
enclosed building to stand as long as possible prior to the application of the cement board. Do not install board
when the board is wet.
Exterior Applications Finishes, leveling/skim coats and basecoats shall not be applied to a DUROCK cement panel that
is wet or frozen or that contains frost. After application, and for at least 24 hours, finishes, leveling/skim coats and
basecoats shall be effectively protected from rain and excessive moisture.
In cold weather and during finish applications,
DUROCK cement panel, skim or basecoat, mortar, finish material
and air temperature must be at least 40 °F, and must remain at this temperature or higher for at least 24 hours
after application. Hot and dry weather may affect working time of leveling/skim or basecoat and finish materials.
Under rapid drying conditions, dampening or light fogging of board, leveling/skim or basecoat surface may be
required to improve workability.
1.5 Steel or wood wall framing to receive DUROCK cement panels shall be structurally sound, free from bow and
Framing
in general compliance with local building code requirements. Damaged and excessively bowed studs shall be
replaced before installation of
DUROCK cement panels. Framing shall be designed (based on stud properties alone)
not to exceed L/360 deflection for tile and thin brick, L/240 for Direct-Applied Exterior Finish Systems. Steel
framing must be 20-gauge equivalent or heavier with corrosion-resistant metal coating equivalent to G60 hot-
dipped galvanized. Exterior steel framing should be laterally braced.
1.6 DUROCK cement panel should be cut to size with utility knife and straight edge. Power saw should be used only
Installation Practices
if equipped with a dust-collection device and a NIOSH/MSHA-approved respirator is worn.
Contractors installing tile and tile-setting materials should always follow current ANSI specifications and
TCNA guidelines.
DUROCK
Cement Board Systems
United States Gypsum Company SA932 9
DUROCK
Cement Board Systems
United States Gypsum Company SA932 10
Part 2: 2.1 A Cement Board
Products
Materials
– DUROCK cement board, 1/2" or 5/8" thickness, 32", 36", or 48" width x lengths of 4' to 10'; exceeds ANSI
A118.9 for cementitious backer units.
–
DUROCK underlayment, 1/4" thickness, 3' width x 5' length, other sizes available.
B Joint Reinforcement—DUROCK tile backer tape (alkali-resistant), 2" x 50', 2" x 150', 2" x 250', or 4" x 150'.
C Fasteners
–
DUROCK tile backer screws for steel framing (No. 8), 1-1/4" and 1-5/8" for 14- to 20-gauge steel framing;
DUROCK tile backer screws for wood framing (No. 8), 1-1/4", 1-5/8", and 2-1/4" for wood framing.
– Nails (1-1/2" hot-dipped galvanized roofing nails).
D Subfloor—5/8" or 3/4" plywood or oriented strand board (OSB), 4' x 8' sheets, exterior grade or superior.
E Adhesives/Mortars
Products compatible with alkaline or portland cement-based
DUROCK cement board include, but are not limited
to the following:
– Meeting ANSI A136.1 Type 1.
– Meeting ANSI A118.1: dry-set mortar mixed with acrylic latex additive.
– Meeting ANSI A118.4: latex portland cement mortar.
F Grout
Products compatible with high pH-based
DUROCK cement board:
– Meeting ANSI A118.6 or ANSI A118.7 or ANSI A118.8.
G Tile—Tile shall meet ANSI A137.1.
H Membrane—DUROCK tile membrane, 15-lb. felt or 4-mil polyethylene membrane, if required, in accordance
with local building codes.
Part 3:
3.1 A Panel Application—Laminate DUROCK cement board to subfloor using Type 1 organic adhesive, latex-fortified
Installation
Floors
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.
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 subfloor. Do not overdrive fasteners. Prefill joints with tile-setting mortar or adhesive and then immediately
embed
DUROCK tile backer tape and level joints.
3.2 A Framing—Space wood and steel framing a maximum of 16" o.c. (24" o.c. for UL Design U459 or U415). The
Walls
studs of freestanding furred walls must be secured to the exterior wall with wall furring brackets or laterally
braced with horizontal studs or runners spaced 4' o.c. max. Laterally brace all steel-framed walls prior to the
application of joint treatment.
B Panel Application—After tub, shower pan or receptor is installed, place temporary 1/4" spacer strips around
lip of fixture. Pre-cut board to required sizes and make necessary cutouts. Fit ends and edges closely but
not forced together, leaving a 1/8" gap. Install board abutting top of spacer strip. Stagger end joints in successive
courses. Fasten panels to framing with specified fasteners. Drive fasteners into field of panels first, working
toward ends and edges. Hold panels in firm contact with framing while driving fasteners. Space fasteners
maximum 8" o.c., 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 framing. Do
not overdrive fasteners. Approved fasteners include:
DUROCK tile backer screws for steel framing (or equivalent),
1-1/4" and 1-5/8" for 14- to 20-gauge steel framing;
DUROCK tile backer screws for wood framing (or equivalent),
1-1/4", 1-5/8", and 2-1/4" for wood framing. Nails (1-1/2" hot-dipped galvanized roofing nails). In double-layer
walls where cement boards are installed over base-layer gypsum boards, apply a vapor-permeable water barrier
over gypsum boards.
C Shaft Wall—Attach DUROCK cement board over base layer of gypsum panels with 1-5/8" DUROCK tile backer
screws for steel framing at 8" o.c. to studs. Since studs are at 24" o.c., laminate cement board to base layer
of gypsum panels with a 4" wide strip of construction adhesive between studs. Apply adhesive with a 1/4"
square-notched trowel.
D Exterior Walls—Attach DUROCK cement board with corrosion-resistant screws spaced a maximum of 8" o.c.
over framing spaced a maximum of 16" o.c. Apply a weather-resistive barrier and flashing behind the panels
as required. Follow the exterior finish manufacturer’s recommendations for application over
DUROCK cement board.
DUROCK
Cement Board Systems
United States Gypsum Company SA932 11
3.3 A Base—Install minimum 3/4" exterior-grade plywood base across wood cabinet supports spaced maximum
Countertops 16" o.c. Position ends and edges over supports.
B Membrane—Staple-attach DUROCK tile membrane, 15-lb. felt or 4-mil polyethylene film using 1/4" galvanized
staples over plywood base.
C Panel Application—Secure DUROCK cement board to plywood. Fasten to plywood with 1-1/4" DUROCK tile backer
screws for wood framing or 1-1/2" hot-dipped galvanized roofing nails spaced 8" in both directions and around
edges; fit ends and edges closely but not forced together, leaving a 1/8" gap.
D Joint Finishing—Prefill joints with latex-fortified mortar or Type 1 organic adhesive; completely embed DUROCK tile
backer tape; and level all joints and outside corners.
3.4 A Framing—Ceiling joists, furring channels or strips must be spaced max. 16" o.c. Framing must be capable of
Ceilings
supporting the total ceiling system dead load, including insulation, ceramic tile, bonding materials and cement
board, with deflection not exceeding L/360 of the span. When steel framing is used, min. 20 ga. is required.
B Panel Application—Apply 1/2" DUROCK cement board to framing with long dimension across framing. Center end
or edge joints on framing and stagger joints in adjacent rows. Fit ends and edges closely, but not forced together,
leaving a 1/8" gap. Fasten boards to steel framing with 1-1/4"
DUROCK tile backer screws for steel framing spaced
6" o.c. and to wood framing with 1-5/8"
DUROCK tile backer screws for wood framing spaced 6" o.c. with perimeter
fasteners at least 3/8" and less than 5/8" from ends and edges. If necessary, provide additional blocking to permit
proper attachment. Edges or ends parallel to framing shall be continuously supported.
3.5 A For Tile and Thin Brick—Prefill all DUROCK cement board joints, and joints where DUROCK cement boards abut
Joint Treatment
other panels or surfaces such as gypsum board, with tile-setting mortar or adhesive, and then immediately
Application
embed tape and level the joints.
B For Dry Untiled Areas—For small areas where the DUROCK cement board will not be tiled, such as a board
extending beyond the tiled area and abutting another surface, treat joints as follows. Seal
DUROCK board with
Type 1 ceramic tile adhesive. (Mix four parts adhesive with one part water.) Embed
SHEETROCK
®
joint tape over
joints and treat fasteners with
SHEETROCK
®
DURABOND
®
setting-type joint compound (45 or 90) applied in conven-
tional manner. Flat trowel
SHEETROCK setting-type joint compound over board to cover fasteners and fill voids to a
smooth surface. Finish joints with at least two coats
SHEETROCK
®
ready-mixed joint compound. Do not apply ready-
mixed or setting-type joint compound over unsealed board.
3.6 A Tile Application—Plan tile layout, then spread latex-modified thin-set mortar or Type 1 adhesive with trowel
Interior
recommended by tile manufacturer held at 45° angle. Apply no more adhesive than can be covered in 20 to 30
Ceramic Tile
minutes. Open time will vary according to temperature and humidity. NOTE: When applying over old ceramic tile,
Application
allow adhesive to set 10 to 15 minutes before applying new tile. Wall tiles may be set top down or bottom up.
Press, do not slide, tiles and sheets of tile into adhesive. Maintain accurate joint alignment and spacing as tiles
are positioned. Use wooden or rubber-faced beating block, tapped lightly with a mallet to level and ensure solid
tile positioning. Check occasionally to ensure at least 95% adhesive transfer to back of tile. Avoid adhesive
squeeze-up between tiles. It may be necessary to butter adhesive on backs of large pavers and quarry tile.
NOTE: Contractors installing ceramic tile should always follow ANSI Specifications and TCNA Guidelines.
B Drying Time—Do not walk on floors for at least 48 hours unless walking boards or plywood sheets are used.
To finish job, wait 24 hours after tile has been installed for walls and countertops, 48 to 72 hours for floors,
before grouting.
C Grouting—Select, prepare and install grout in accordance with recommendations provided by grout manufacturers.
3.7 A Follow the exterior finish manufacturer’s recommendations for finishes applied to DUROCK cement board.
Exterior Applications
B
It is recommended that a weather resistive barrier and flashing be installed behind DUROCK cement board in
direct-applied finish applications to provide a means for draining any intruding moisture safely from the exterior
of the building.
C Follow the manufacturer’s recommendation, design professional, or contract documents for proper sealants and
flashings at openings such as windows and doors.
DUROCK
Cement Board Systems
Manufactured by
United States Gypsum Company
550 West Adams Street
Chicago, IL 60661
SA932/rev. 1-12
© 2012 United States Gypsum Company
Printed in U.S.A.
Metric Specifications
USG Corporation, through its
operating subsidiaries, will provide
metric conversions on its products
and systems to help specifiers
match metric design sizes. In
addition, some products are
available in metric dimensions
from selected manufacturing
plants. Refer to SA100
Construction Selector for additional
information and a Table of Metric
Equivalents.
Trademarks
The following trademarks used
herein are owned by United States
Gypsum or a related company:
DUROCK, DIAMOND, DURABOND, FIBEROCK,
F
IRECODE, IMPERIAL, MOLD TOUGH,
S
HEETROCK, USG, USG in stylized
letters.
THERMAFIBER is a trademark of
THERMAFIBER LLC.
Notice
We shall not be liable for incidental
and consequential damages, directly
or indirectly sustained, 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.
Note
All products described here may
not be available in all geographic
markets. Consult your local sales
office or representative for
information.
Safety First!
Follow good safety and industrial
hygiene practices during handling
and installing all products and
systems. Take necessary precau-
tions and wear the appropriate
personal protective equipment
as needed. Read material safety
data sheets and related literature
on products before specification
and/or installation.
Websites
usg.com/durock
usgdesignstudio.com
Technical Service
800 USG.4YOU
usg4you@usg.com
Samples/Literature
samplit@usg.com
Customer Service
800 621.9523