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Introduction
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Scope of Work
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Guide Specifications

Part I:General
1.01 Scope
This specification covers the minimum requirements for the application of a stucco
system, including general information pertaining to the design and application of stucco.

NOTE:
• This specification serves as a guide for the development of a specification
for a particular project.

1.02 Contractor Scope of Work
The work of this section includes all the equipment, materials and labor necessary to
complete a stucco system, as indicated in this Stucco Resource Guide and/or in project
documents (drawings and specifications).

1.03 Related Sections (Section numbers may be different depending upon specification format)

A. Section 01200 — Project Meetings
B. Section 01630 — Substitutions

NOTE:

• Product substitutions will be considered only under the terms and
conditions of section 01630.

C. Section 03300 — Concrete
D. Section 04220 — Unit Masonry
E. Section 05410 — Load-Bearing Steel Studs
F. Section 06110 — Wood Framing
G. Section 07240 — Exterior Insulation and Finish Systems
H. Section 07600 — Flashing and Sheet Metal
I. Section 07900 — Joint Sealants
J. Section 09110 — Non-Load-Bearing Steel Studs
K. Section 09250 — Gypsum Sheathing Board
L. Section 09900 — Painting

Details in this Stucco Resource Guide may show a single layer of water-resistant
barrier for drawing clarity only. Refer to the Guide Specification
section 3.38-B. The recommendation is for two layers.

1.04 Reference Standards

A. National Building Code — Canada
B. City Building Code — Vancouver, B.C.
C. Building Codes - International, NFRA, California, Uniform
D. Stucco Resource Guide (NWCB)
E. American Concrete Institute ACI 524R: Guide to Portland Cement Plastering
F. Federal Specifications FS UU-B-790a: Building Papers, FS FF-N-105B: Nails, Wire Staples for Application of Gypsum Board, FS QQ-W-461H: Wire, Steel and Carbon (round , bare & coated)
G. Portland Cement Plaster (Stucco) Manual by PCA
H. ASTM Standards

ASTM A526: Steel Sheet, Hot-Dip Galvanized, Commercial Quality
ASTM C91: Masonry Cement
ASTM C144: Aggregate
ASTM C150: Portland Cement
ASTM C1328: Plastic Cement
ASTM C206: Hydrated Lime
ASTM C260: Air-Entraining Admixtures
ASTM C494: Chemical Admixtures for Concrete
ASTM C841: Installation of Interior Lathing and Furring
ASTM C847: Metal Lath
ASTM C897: Aggregate for Job-Mixed Portland Cement Plaster
ASTM C926: Application of Portland Cement-Based Plaster
ASTM C932: Surface-Applied Bonding Agents for Exterior Plastering
ASTM C979: Pigments for Integrally Colored Concrete
ASTM C1032: Woven Wire Plaster Base
ASTM C1063: Installation of Lathing and Furring for Portland Cement Plaster
ASTM D1784: Rigid Poly (Vinyl Chloride) PVC Compounds



I. NAAMA Standard ML/SFA 920

NOTE:
• Current editions at date of bid.
• Use references and standards applicable to project.

1.05 Standards for Work
All work to be performed per Northwest Wall and Ceiling Bureau recommendations.
A. Stucco Resource Guide and project construction documents.

NOTE:
• Project construction documents to indicate type of stucco assembly.
(Refer to “Stucco Assemblies” section of this Stucco Resource Guide).

1.06 Submittals

A. Submittal requirements by the stucco contractor are to be indicated in the construc-tion documents. The following is a list of documents that may be requested.

1. Product literature.
2. Samples and/or mock-ups of system.
3. Certification of compliance of materials and/or product literature.
4. Product literature for all additives and proprietary components.
5. Finish sample for texture and color for architect/owner approval.

NOTE:
• Delete submittals not required.
• Plastering contractor is not to proceed with work until the required
submittals have been approved.

1.07 Quality Assurance for Scope of Stucco Work

A. Pre-installation meeting.
B. Wall assembly fire-resistance rating: _______ hour(s).

NOTE:
• Construction documents shall indicate the type of fire and/or sound
assembly rating required for project.
• Construction documents to indicate fire-resistance assembly test
required.

C. “Scope of Work Responsibilities Tables” section of this Stucco Resource Guide.
D. “Stucco Quality Assurance Checklist” section of this Stucco Resource Guide.
E. If required and feasible, an approved finish coat on a portion of the building.
Location of finish coat sample as directed by the architect.

NOTE:
• Delete if not applicable.

F. Applicator qualifications. The plastering company shall meet the following
requirements:

1. Specialize in this scope of work.
2. Have qualified and properly trained people to perform work.
3. Be licensed, bonded and insured.
4. Be in good financial standing and capable of meeting the financial obligations
associated with the stucco scope of work on the project.
5. Have documented experience in quality work of comparable scope.
6. Be recommended as a qualified installer by NWCB or national or regional Wall
and Ceiling Association (Plastering Association) or approved by architect prior
to bid.
7. Contractor shall be able to meet schedule requirements set at time of bid.

1.08 Delivery, Storage, Handling and Setup

A. Materials at job site to be in original containers with labels intact and legible.

NOTE:
• Exception: Basecoat sand

B. All trim accessories and lath and/or other specified products to be shipped to job site
in original containers. Any damaged or bent materials shall be replaced.
C. All sack materials to be stored above ground, dry and protected.

NOTE:
• General contractor shall provide suitable site for delivery, storage and
handling of materials.
• General contractor shall provide suitable site for plastering operation.

1.09 Environmental Conditions

A. Cold Weather Conditions:

1. Do not apply cement plaster when ambient temperature is less than 35....F (2....C).
2. Do not apply cement plaster to any frozen surfaces or surfaces containing frost.
Protect plaster coats against freezing for a period of 24 hours after application.
3. Do not use frozen materials.
4. Hoarding (tenting), heat and ventilation must be provided if cement plastering
is done in a temperature below 35....F (2....C).

NOTE:
• The plastering contractor is not responsible for these requirements.
• Maintain adequate ventilation. Vent heaters to outside.

5. Admixtures of cement plaster for cold weather condition must be approved and
used in accordance of manufacturer’s recommendations.

B. Warm Weather Conditions:

1. Protect the basecoats and finish coat of cement plaster from uneven and
excessive evaporation in warm, windy weather. (Refer to section on curing in
Part III)

NOTE:
• Moist-curing is recommended.

Part II:Products

2.01 Weather-Barrier Backing/Water-Resistant Barrier

A. Water-resistant paper—Federal Specification UU-B-790a, grade D/30-minute or 60-
minute
B. Spunbonded olefin housewrap manufactured and designed specifically for stucco.
C. Flashing material around rough wall openings shall be a reinforced coated vapor-barrier,
grade A or B product, sheet metal, PVC plastic, or other approved
membrane. The application of the flashing is not the responsibility of the stucco contractor. Refer to the “Scope of Work Responsibilities” section of this Stucco
Resource Guide.

2.02 Window head, door, louver and/or other penetration-plus wall opening pan-type flashing - 26-gauge galvanized sheet metal, or PVC plastic.

NOTE:
• Construction documents to indicate responsibility for installation of
window head flashing and other stucco component flashing.

2.03 Tie Wire

Hanger and tie wire to be galvanized and annealed low-carbon steel:
FSQQ-W-461g. AS
A. Hanger wire No. 8—.1620 inch (4.12 mm)
B. Tie wire 18 gauge—.0475 inch (1.22 mm)
C. Tie wire 16 gauge—.0625 inch (1.59 mm)

2.04 Runner- and Cross-Furring Channels

Cold-rolled galvanized steel channels, 1 1/2 inches (38 mm) and 3/4 inches (19 mm), a
minimum of 33,000 psi yield strength and a minimum of .0538-inch bare steel thickness,
ASTM A526.

NOTE:
• Suspended soffits/ceilings—1 1/2-inch (38 mm) main runner, 3/4-inch (19
mm)
cross furring.

2.05 Furring “Hat” Channels
Furring channel, galvanized 7/8-inch (22 mm), 20-gauge.

2.06 Fasteners Shall Comply with:
A. Nails—FS FF-N-105
B. Staples—FS FF-N-105
C. Screws—ASTM C 646
D. Power-driven fasteners—per building code approval

NOTE:
• All fasteners to be corrosion-resistant and new.

2.07 Lath

NOTE:
• Architect/specifier to indicate in construction documents the type or
types of lath (A, B, C or D). Delete types of lath not applicable.
• Self-furring paperback lath (a combination of lath and grade D 60-
minute water-resistant barrier)
is not recommended over a vertical
concrete or concrete masonry surface if the construction documents.
require a water-resistant barrier for these surfaces.
A. Self-furring woven wire lath 17 gauge—1 1/2-inch (38 mm) opening, galvanized.
Shall comply with ASTM 1032.

NOTE:
• For vertical surfaces only.
B. Self-furring diamond-mesh metal lath galvanized, 2.5 or 3.4 pounds per square yard.
Shall comply with ASTM 847.

NOTE:
• 2.5-pound-per-square-yard self-furring lath may be used for a sheathed
framing construction system, 16 inches (400 mm) o.c., or for attachment
directly to concrete or concrete masonry.

C. Self-furring welded wire lath, 16 gauge wire, galvanized openings not to exceed 2
inches x 2 inches (50 mm x 50 mm). Shall comply with ASTM 933.

NOTE:
• For vertical surfaces only.
D. 3/8-inch (10 mm) rib lath, galvanized. ASTM 847

NOTE:
• For soffit condition with open-frame construction, with supports 24
inches (600 mm) o.c.

2.08 Trim Accessories

NOTE:
• Trim Accessories shall be fabricated from galvanized steel, zinc (alloy),
PVC or anodized aluminum.
• Depth (the grounds) of accessories depends on the required thickness of
cement plaster basecoat, without the finish coat.
• If the construction documents do not indicate the type of accessories to
be installed, the plastering contractor shall select the accessories in
accordance with these standards.
• Accessories of PVC plastic or zinc (alloy) are recommended if corrosion
is a concern because of environmental conditions.
• Accessories with a finish surface lip flange and/or embedment flange to
key into cement plaster are recommended.
• It is recommended that PVC or aluminum reveals, when used in
conjunction with 2-inch x 2-inch welded wire lath, incorporate a strip of
expanded metal lath over the solid reveal flanges.

A. Steel accessories per ASTM C 841
B. PVC plastic accessories per ASTM D 1784 & C 1063
C. Aluminum accessories from extruded alloy 6063 T5
D. General types of accessories:

1. Foundation weep screed: ______________________________________
2. Casing bead type no. 66 (JMOLD): _______________________________
3. Corner reinforcement (corner bead): ______________________________

NOTE:
• No. 1A expanded corner beads for interior gypsum plaster are not
recommended.
E. Soffit vents ______________________________
F. Drip screeds ______________________________
G. Trim accessory joints (control joints), expansion joints, or revels____________

NOTE:
• Construction documents shall reference type, style and manufacturers of
accessories.
• Delete accessories not applicable for the project.

2.09 Bonding Agents
Bonding agents must conform to ASTM C 932, nonoxidizing, non-crystallizing,
non-re-emulsifiable.

NOTE:
• Apply per manufacturer’s recommendations.
• Apply bonding agents only to clean, structurally sound surfaces
(concrete, concrete masonry and cement plaster).
• Indicate manufacturer and brand name.
• Delete if not applicable.

2.10 Plaster Materials

NOTE:
• Delete cements not applicable.
A. Stucco basecoat

1. Portland Cement: ASTM C 150 Type I or Type I/II
2. Masonry Cement: ASTM C 91 Type I or Type I/II
3. 1-P Portland Cement: ASTM C 595
4. Manufactured basecoat cement for stucco

NOTE:
• Indicate manufacturer as per NWCB and/or regional wall and ceiling
association recommendation.
B. Hydrated lime: ASTM C 206 Type S
C. Stucco finish

1. White portland cement, ASTM 150 Type I or Type I/II
2. Regular portland cement, ASTM 150 Type I or Type I/II
3. Manufactured stucco finish

NOTE:
• Indicate manufacturer as per NWCB and/or regional wall and ceiling
association recommendation.

NOTE:
• Do not use frozen aggregate.
A. Basecoat sand

NOTE:
• ASTM C144 or C897
• Natural or manufactured
• Washed and free of deleterious materials
• Locally available sand that approximates ASTM C144 or C897, but
which may be nonconforming, can be approved for use if past perfor-mance
indicates that it is an appropriate material.
B. Finish coat sand

NOTE:
• ASTM C897
• Natural or manufactured
• Freshwater washed and free of deleterious materials
• Locally available sand that approximates ASTM C144 or C897, but
which may be nonconforming, can be approved for use if past perfor-mance
indicates that it is an appropriate material.

2.12 Water Potable, clean, free from impurities.

2.13 Admixtures

NOTE:
• No household-type detergents or chlorides shall be permitted.
• Only admixtures manufactured specifically and approved for use in a
stucco mix shall be permitted.
• Admixtures without supporting documentation and appropriate testing
or industry performance will not be approved by the NWCB and/or
regional wall and ceiling association.
A. Fibers: 1/2-inch (13 mm) long, ASTM C 1116

NOTE:
• Recommended as part of basic basecoat mix.
• Only in basecoats, not in finish coat.
• Polypropylene, nylon or alkali-resistant glass fibers.
• Use only types specifically manufactured for a stucco basecoat and per
manufacturer’s recommendations.

B. Air-entraining admixtures:

NOTE:
• ASTM C 260
• Amount used shall be consistent with manufacturer’s recommendations.
• Use only products approved by the NWCB and/or regional wall and
ceiling association.
C. Water-reducing admixtures

NOTE:
• ASTM C494, Type A
• Amount used shall be consistent with manufacturer’s recommendations.
• Use only products approved by the NWCB and/or regional wall and
ceiling association.
D. Accelerating admixtures

NOTE:
• ASTM C494, Type C and E.
• Must be non-chloride or chloride with rust-inhibitors.
• Amount used shall be consistent with manufacturer’s recommendations.
• Use only products approved by the NWCB and/or regional wall and
ceiling association.
E. Pump-aid admixtures

NOTE:
• Amount used to be consistent with manufacturer’s recommendations.
• Use only products approved by the NWCB and/or regional wall and
ceiling association.

2.14 Coloring Compounds for Job-site Stucco Finish

NOTE:
• Delete if not required.
• “A” prepackaged colors recommended rather than “B” raw color
pigments.
A. Prepackaged colors

NOTE:
• ASTM C979
• Use only coloring compounds manufactured for a job-site stucco finish.
• Identify manufacturer, brand name and color code.
• Mix with finish coat materials according to manufacturer’s recommen-dations.
• Best color uniformity can be achieved with prepackaged products.
B. Raw Color Pigments

NOTE:
• ASTM C979
• Natural or synthetic iron oxides
• Identify manufacturer, brand name and color code.
• Mix with finish coat materials in proportions which replicate a
previously approved sample.
• Variation in the uniformity of color is normal when raw pigments are used.

2.15 Mix Proportions

NOTE:
• Proportions are parts by volume for basecoats and job-site stucco finish
coat.
• Use standard measuring devices and know volumes for all materials.
• Sequential batches to be proportionally alike.
• All mixing in a mechanical mixer.
• Continue to mix for 3-5 minutes after all ingredients have been added.
• Add fibers 2-3 minutes before mixing is complete.
• Factory-prepared stucco finish coat per manufacturer’s requirements.
• Admixtures per manufacturer’s requirements.
• Cement materials shall be based on full bag increments.
• Shovel count can be used for measuring sand if standardized first.
• Use enough water to produce suitably plastic cementitious material,
keeping water to a minimum.
• Sequence of materials: (1) water, (2) half of sand, (3) all of the cement
and/or lime, (4) balance of sand and (5) water for workability.
• “Brown” coat may contain the higher volume of sand.
• For integral color finish, factory-prepared finishes will result in truer
and more consistent color.
• Sand per sum of cementitious material.
• For mix no. 1, 3, 4 and 5, volume of sand in first coat shall the same or
less than volume in the second (brown) coat, not to exceed 4 parts of
sand per sum of cementitious materials.
• For mix no. 2, volume of sand in first coat shall be the same or less than
volume in the second (brown) coat, not to exceed 3 1/2 parts of sand per
sum of cementitious materials.
• Amount of fibers per mix per manufacturer’s recommendations.
A. Basecoat mix parts by volume (ASTM C 926) and finish coat mix parts by volume
(ASTM C926)

NOTE:
• Select one of the five mixes or another approved ASTM C926 mix for the
project. Do not interchange components. Once project has been started,
do not switch to another mix.
• Architect to indicate which one of the five mixes to use. If mix is not
shown in construction documents, plastering contractor may use one of
the five mixes shown in this Guide Specification.
• Delete mixes not to be used in the project.
• Volume of sand per sum of cementitious material.

Mix No. 1—Basecoat
Portland cement .............................. 1
Masonry cement ............................. 1
Sand ............................................ 3 1/2 - 4 1/2
Fibers ............................................ per manufacturer’s recommendations
Mix No. 2—Basecoat
Portland cement .............................. 1
Lime ............................................ 1/4 - 1/2
Sand ............................................ 3-4
Fibers ............................................ per manufacturer’s recommendations
Mix No. 3—Basecoat
1-P portland cement ........................ 1
Masonry cement ............................. 1
Sand ............................................ 3 1/2 - 4 1/2
Fibers ............................................ per manufacturer’s recommendations
Mix No. 4—Basecoat
Plastic cement ................................. 1
Sand ............................................ 3 1/2 - 4 1/2
Fibers ............................................ per manufacturer’s recommendations
Mix No. 5—Basecoat
Portland cement .............................. 1
Plastic cement ................................. 1
Sand ............................................ 3 1/2 - 4 1/2
Fibers ............................................ per manufacturer’s recommendations

B. Job-site stucco finish coat
White portland cement.................... 1
(or regular portland cement)
Lime ............................................ 1 - 2
Sand ............................................ 3

NOTE:
• Add manufactured coloring compounds to job-site stucco finish mix per
manufacturer’s recommendations.
• Delete if not applicable.
C. Manufactured stucco finish

NOTE:
• Mix and apply per manufacturer’s recommendation.
• Manufacturer to be approved by NWCB and/or regional wall and ceiling.

2.16 Acrylic Finish

NOTE:
• A proprietary finish material by EIFS manufacturer, approved by NWCB
and/or regional wall and ceiling association.
• 100-percent acrylic polymer material in finish.
• Mix and apply per manufacturer’s recommendations.
• Delete if not applicable.

Part III:Execution

3.01 Examination
A. Prior to starting lathing or plastering work, carefully inspect installed work of other
trades to verify that work is complete to the point where work of this section may
properly commence.
B. Notify the architect or proper authorities in writing of conditions detrimental to the
proper and timely completion of the lathing and/or plastering work.
C. Do not begin installation until all unsatisfactory conditions are resolved.
D. A pre-construction meeting is recommended with the architect and/or owner, primary
contractor and representatives responsible for the windows, framing, flashing, roofing,
sealants, stucco and any other building components interfacing with the stucco.

NOTE:
• The examination of conditions is the responsibility of all parties involved
in the project.

3.02 Performance
A. The work shall be performed by a skilled and trained work crew.

NOTE:
• Work shall be performed to create a rigid, secure, level or plumb finish
surface, with line dimensions and/or contours as indicated in reference
standards or project documents.

B. Install specified products and/or systems in accordance with reference standards,
manufacturer’s recommendations and this Stucco Resource Guide, unless indicated
otherwise in project documents.
C. Flashings shall be installed prior to start of lathing or may be required to be
integrated at the time of lathing. Flashing is not the scope of work of the contractor
responsible for the stucco assembly.

3.03 Installation of Stucco Trim Accessories

NOTE:
• Refer to details and other portions of this Stucco Resource Guide for
additional information

A. Verify that substrate and work by other trades are complete to the point at which
installation of trim accessories may properly commence.

NOTE:
• Do not begin work until unsatisfactory conditions are resolved.
B. Attachments shall be firm enough to hold trim accessories in place without
misalignment during plastering.

NOTE:
• Flanges or attachment points of trim accessories shall be secured
to substrate in accordance with requirements of manufacturers of
approved fasteners. Space per manufacturer’s directions.
• It is recommended that PVC or aluminum reveals, when used in
conjunction with 2-inch x 2-inch welded wire lath, incorporate a strip of
expanded metal lath over the solid reveal flanges.

C. It is recommended that trim accessories have a small top flange “lip” that goes over
the stucco and/or flange that embeds into the stucco.
D. Zinc alloy or PVC is recommended if trim accessories are exposed to a high-salt
environment.
E. Install individual trim-accessory sections to each other at end joints for accurate
alignment.
F. Install trim accessories in a manner that ensures a true, level and plumb stucco
surface, and moisture resistant.

NOTE:
• Accurate alignment of trim accessories may require shimming, limited to
the thickness of stucco.
• Sections of flashing or trim accessories that butt each other (at corners
or another condition)
need to be lapped, caulked, or have a strip of self-adhering
membrane over the joints. This is to prevent moisture from
getting to the building structure.

G. Install the trim accessories in accordance with the required thickness of stucco
basecoat and finish coat requirements. (Refer to Plaster Thickness section)

NOTE:
• Depth (grounds) of trim accessory to be in accordance with the
thickness of stucco. (Refer to Plaster Thickness Tables)
For example, 3/4-inch (19-mm) stucco requires a minimum ground of a
casing bead to be 3/4 inch (19 mm).

H. Install the longest possible lengths of trim accessories. A minimum continuous
section (length) of 7 feet (2 m) is recommended.

3.04 Trim Accessory Joints

NOTE:
• Installation to be in accordance with section 3.03—Installation of
Stucco Trim Accessories.
• Trim accessory joints refer to various types: control joints, expansion
joints, reveals, and/or any other devices or systems that divide (break) the
stucco membrane surface.
• Architect is to select the type of joint and indicate on drawing the
location of joints.
• Trim accessory joints provide relief of stresses from the structure and
cement-plaster curing process.
• Trim accessory joints provide for a plaster stop and a screed.
• Aluminum and/or PVC reveals require that when the lath is installed
over the flange, it totally covers it. The welded wire and woven wire lath
shall be installed so as the crotch of the lath is over the flange.
• It is recommended that PVC or aluminum reveals, when used in
conjunction with 2-inch x 2-inch welded wire lath, incorporate a strip of
expanded metal lath over the reveal flanges.

A. The water-resistant barrier must continue unbroken behind trim accessory joints in
vertical or horizontal direction.

B. Locate to trim accessory joints strategically at points where building movement is
anticipated.

1. Wall penetrations
2. Structural plate lines
3. Junctures of dissimilar substrates
4. Existing construction joints in structure
5. Columns
6. Cantilevered areas

C. Joints are recommended in stucco assemblies with lath reinforcement but have
limited use in direct-applied stucco over concrete or concrete masonry surface.
D. It is recommended that trim accessory joints be weather-sealed by embedment in
caulking at intersections when placed end-to-end and at the terminations.
E. It is recommended to install vertical joints continuously and to abut horizontal joints
to vertical (be sure that water-resistant barrier runs continuously behind joints).

NOTE:
• The use of horizontal reveals, flashing designs and/or other horizontal
surface breaks may prevent continuous vertical joints.
• Expansion joints govern over control joints.

F. Install longest possible lengths. No termination of a section within 24 inches (600
mm)
of an intersection, with the exception of pre-manufactured trim accessory joint
intersections.

G. It is recommended that trim accessory joints be installed on framed, sheathed
construction so as to create stucco panel of 150 to 180 square feet (14 m 2 to 17 m 2 )
in as square a configuration as possible.

NOTE:
• Maximum recommended length of a panel is 18 feet (5.5 m). Panel size
approximately 3-to-1 ratio.

H. It is recommended that trim accessory joints be installed with concrete or concrete
masonry construction so as to create a stucco assembly (with lath reinforcement) of
200 to 250 square feet (18 m 2 to 23 m 2 ).
I. Installing control joints over continuous lath is an approved method.

NOTE:
• Control joint is a one-piece trim accessory.
• Control joint may be installed in the “field of panel” only if there is
framing or wood sheathing continuous substrate behind it for attachment.
• Control joints to be wire tied to lath with 18-gauge tie wire (recom-mended
method when lath goes over sheathing board other than wood).

J. The recommendation for the installation of expansion joints or reveals is to break the
lath and lap it over on top of each of the flanges.

NOTE:
• Control joints may also serve as expansion joints, if so specified and
detailed.
• Expansion joints and/or reveals may consist of one or two pieces.
• Control joints are limited in their degree of movement. Two-piece
expansion joints provide greater movement.
K. Sheathed framed construction with vertical trim accessory joints that require the lath
to be terminated (cut) and installed on top of the flanges shall be placed at framing
member locations. Lath shall be attached with appropriate fasteners through the
trim accessory flange, sheathing and into the framing member.

NOTE:
• The lath/flange on each side of the trim accessory joint to be attached to
a framing member. Double framing supports would be required at these
locations.
• This condition does not pertain to control joints installed over continu-ous
lath.

3.05 Lathing for Soffits

A. Suspended soffits/ceilings shall be erected so that the finished basecoat cement
plaster surface is true to line and level, with allowable tolerance of 1/4 inch (6 mm)
in 10 feet (3.1 m)

NOTE:
• Construction documents shall indicate the approximate amount of
deflection of structure to which suspended soffit is attached..34 Northwest
• No attachment of soffit/ceiling abutting to walls or fascia (in order to
prevent transfer of stresses)
.
• Vertical compression struts to withstand upward wind pressures are not
required unless indicated in project documents.
• NWCB recommends a soffit framing system with sheathing (refer to
3.06-B)
because it incorporates a gypsum sheathing board attached to
furring “hat” channels. This type of assembly produces a better stucco
soffit. The sheathing board provides rigidity to the framing system and
helps produce a uniform stucco thickness.
• Refer to sections 3.03 and 3.04.

B. Spacing, attachment, size and type of hangers, fasteners and inserts shall be as
required in reference standards in section 1.04.
NOTE:
• Fasteners and inserts shall have up-to-date testing information from
manufacturers.

3.06 Lathing Systems for Suspended Soffits (for details, see soffit section)

NOTE:
• For additional suspended soffit configurations (size, spans and spacing),
refer to reference standards in section 1.04. (ASTM C1063)
• Construction documents to indicate either the soffit framing system
(refer to 3.06 A) or soffit framing system with sheathing (refer to 3.06 B).

A. Soffit framing system

1. Hanger wires maximum support 16 square feet (1.5 m 2 )
2. 1 1/2-inch (38-mm) main runner channels o.c. spacing 48 inches (1.2 m)
3. 3/4-inch (19-mm) cross-furring channels o.c. spacing 13 to 16 inches (325 to
400 mm)

4. 3.4-pound-per-square-yard diamond-mesh lath
5. Wire-tie lath to cross-furring channels with 18-gauge tie-wire, 6 inches (150
mm)
o.c.

B. Soffit framing system with sheathing

1. Hanger wires, maximum support 16 square feet (1.5 m 2 )
2. 1 1/2-inch (38-mm) main runner channels, maximum o.c. spacing 48 inches
(1.2 m)
3. 20-gauge furring “hat” channels, spaced maximum 16 inches (400 mm)
4. 1/2-inch (13-mm) gypsum sheathing board
5. 3.4-pound-per-square-yard self-furring diamond-mesh lath attached through
gypsum sheathing board into furring channels, maximum 6 inches (150 mm)
o.c. with type S screws—wafer head—1 inch (25 mm) long.35 Northwest

3.07 Soffit Lathing System to Wood Joist
A. 3/8 inch (10 mm) rib lath attached 6 inches (150 mm) o.c., with one of the following:

1. Roofing nails: 11 gauge • 7/16-inch diameter head • 1-inch long
2. Staples: 16 gauge • 3/4-inch crown • 1 1/4-inch long
3. Screws: type W • wafer head • 1-inch long

NOTE:
• Fasteners must penetrate into the wood a minimum of 3/4 inch (19 mm)
both legs of staple must penetrate wood. Fasteners to be centered,
minimum 3/8 inch (10 mm) from edge of wood joist.
• Maximum spacing of wood joist 24 inches (600 mm) o.c.

3.08 Application of Stucco Basecoat for Soffits

NOTE:
• Do not use the double-back method of applying the basecoats.
• Verify trim accessories and lath are installed so as to provide proper
screeds, thickness and alignment for plastering.
• Do not begin plastering work until unsatisfactory conditions are resolved.
• Cement plaster can be applied by trowel or machine.
• Apply basecoat to entire horizontal surface and/or section without
interruption or “cold joints.”

A. Indicate the permissible mix number and its proportions to be used for the basecoat

NOTE:
• Delete basecoat mixes not applicable to this project.
• Do not change selected mix or proportions after plastering operation has
started.
• Measurement of ingredients (materials of the mix) to be done with
devices of known volume, accurate, and successive batches proportion-ally
alike.
• Use only enough mix water to make plaster a workable consistency.
• Admixtures to be submitted for approval.
• Basecoat admixtures designed for improving the mix or for enhancing the
plaster application must have been manufactured strictly for that
purpose.
• Admixtures must be accurately measured and used only in accordance
with manufacturer’s recommendations.

B. Apply stucco first (“scratch”) coat in a nominal thickness of 3/8 inch (10 mm). First
coat to completely embed the lath. First coat to be thick enough to allow for scoring
of cement plaster surface. (Refer to Plaster Thickness Tables)

NOTE:
• Scoring of the first coat should be uniform and shallow, approximately 1/
8 inch (3 mm).
C. Moist cure the first (“scratch”) coat for a minimum of 48 hours before application of
the second (“brown”) coat.

NOTE:
• First coat to be hard and rigid before receiving the second coat.
D. Apply stucco second (“brown”) coat in a nominal thickness of 3/8 inch (10 mm)
over stucco first coat. Second coat thickness to bring the combined basecoats (first
and second)
thickness to a nominal thickness of 3/4 inch (19 mm). (Refer to Plaster
Thickness Tables)

NOTE:
• Apply second coat over a damp first coat. If required, apply a fine spray
of clean water, so as to dampen only. Do not saturate. Allow water
sheen to disappear before applying the second coat.

E. Apply the second coat with sufficient material and pressure to ensure a tight uniform
bond to the first coat.

NOTE:
• Apply second coat so as not to deform or crack the first coat.

F. Rod the second coat to a true, even plane, filling surface defects with cement plaster.
G. Trowel-float the second coat surface uniformly.

NOTE:
• The floating process densifies the basecoat and provides a proper surface
for the finish coat application.
• Float the basecoat after it has set and when moisture is still present in it.
• Floating the basecoat that is to receive an acrylic finish coat is critical
because of the thickness of this finish.

3.09 Curing of Soffit Basecoat—Refer to section 3.40.
NOTE:
• After the second coat has been applied, moist cure it as required, and then
wait a minimum of seven days before the start of finish coat application.
3.10 Stucco Finish Coat—Refer to section 3.41.
3.11 Acrylic Finish Coat—Refer to section 3.42.
3.12 Additional Types of Finishes—Refer to section 3.43.
3.13 Cement Plaster Direct to Concrete

NOTE:
• Concrete to be cured for a minimum of 28 days..37 Northwest
• Not recommended for horizontal surfaces (other than ceilings/soffits).
• Concrete surface to be straight and true, in accordance with standards.
• Concrete surface to be clean, no form release agents, no curing compounds
or other elements in concrete surface preventing a proper bond.
• Concrete should be in good condition and have uniform absorption rate
over entire surface.
• Concrete in poor condition (spalling, delamination, voids) or other
surface defects requires repair before plastering.
• If the concrete surface is not in proper condition, self-furring lath must
be installed.
• If there is any concern about the bondability of the cement plaster direct
to concrete, a test area is recommended. Apply 1/4” - 1/2” thick, by 1’x1’
of cement plaster basecoat to concrete; let it cure for 3 - 4 days. Then try
to remove it. Do this type of test at more than one location.
• Acrylic finish coat is not recommended for concrete retaining walls.
3.14 Stucco “Finish Coat” Direct to Concrete—Refer to “Stucco Wall Assemblies” section
detail A6 in this Stucco Resource Guide.

NOTE:
• The finish coat over concrete is used to enhance the surface appearance;
it is not designed to “true up” the surface.
• Smooth troweled stucco finishes are not recommended because of the
possibility of very fine map cracking. If smooth troweled finish is specified,
surface should be painted with a high-quality acrylic exterior paint.

A. Apply liquid bonding agent directly to concrete surface in accordance with the
recommendation of manufacturer of the material.
B. Application of the stucco finish coat—Refer to section 3.41.

3.15 Acrylic Finish Coat Direct to Concrete—Refer to section 3.42.
NOTE:
• Do not apply finish until all irregularities on the concrete surface have
been corrected.

3.16 Two Coat Stucco Direct to Concrete—Refer to “Stucco Wall Assemblies” section
detail A7 in this Stucco Resource Guide.

NOTE:
• This method provides for an economical way of creating an acceptable
level finished wall surface.
• The system provides a leveling basecoat (brown coat) over the concrete
surface and makes a suitable base for the finish coat with limited total
stucco thickness of 1/2 inch (13 mm).
• Refer to section 3.13..38 Northwest

A. Apply liquid bonding agent directly to concrete surface only in accordance with the
recommendation of manufacturer of the material.
B. Install trim accessories—termination trim accessory, corner reinforcements (corner
beads), trim accessory joints (control joints) and other specified accessories in
accordance with sections 3.03 and 3.04.

NOTE:
• Install per related detail sections of this Stucco Resource Guide.
• Delete trim accessories no