Applying One- And Two-Coat Veneer Plaster Over A Gypsum Base

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We’ve reviewed these procedures for general consistency with federal standards for rehabilitating historic buildings and provide them only as a reference. Specifications should only be applied under the guidance of a qualified preservation professional who can assess the applicability of a procedure to a particular building, project or location. References to products and suppliers serve as general guidelines and do not constitute a federal endorsement nor a determination that a product or method is the best alternative or compliant with current environmental regulations and safety standards.




A. This procedure includes guidance on applying plaster
veneer over a gypsum base. This also includes the
following work:

1. Steel framing members to receive gypsum base.

2. Gypsum base screw-attached to steel framing and
furring members.

3. One-component veneer plastering over gypsum base.

B. Screw type metal support system and furring are specified
elsewhere in Division 9.

C. Shaft walls constructed with gypsum base face layers are
specified in Division 9 specification for Gypsum Board
Shaft Wall Systems.

D. See 01100-07-S for general project guidelines to be
reviewed along with this procedure. These guidelines
cover the following sections:

1. Safety Precautions

2. Historic Structures Precautions

3. Submittals

4. Quality Assurance

5. Delivery, Storage and Handling

6. Project/Site Conditions

7. Sequencing and Scheduling

8. General Protection (Surface and Surrounding)

These guidelines should be reviewed prior to performing
this procedure and should be followed, when applicable,
along with recommendations from the Regional Historic
Preservation Officer (RHPO).


A. Gypsum Board Construction Terminology: Refer to ASTM C11
for definitions of terms for gypsum board construction
not otherwise defined in this procedure or other
referenced standards.


A. Performance Requirements:

1. Fire-Resistance Ratings: Where indicated, provide
materials and construction which are identical to
those of assemblies whose fire resistance rating
has been determined per ASTM E119 by a testing and
inspecting organization acceptable to authorities
having jurisdiction.

a. Provide fire-resistance-rated assemblies
identical to those indicated by design
designations in U.L. "Fire Resistance
Directory" or in listing of other testing and
agencies acceptable to authorities having


A. Product Data: Submit manufacturer's product specifications and installation instructions for each
veneer plaster and gypsum basecoat component, including
other data as may be required to show compliance with
this procedure.


A. Qualifications: Single Source Responsibility: Obtain
veneer plaster products (gypsum base, joint reinforcing,
and veneer plaster) from a single manufacturer for each
veneer plaster system indicated.


A. Packing and Shipping: Deliver materials in original
packages, containers or bundles bearing brand name and
identification of manufacturer or supplier.

B. Acceptance at Site: Handle gypsum base to prevent damage
to edges, ends, and surfaces. Do not bend or otherwise
damage metal corner beads and trim.

C. Storage and Protection: Store materials inside under
cover and keep them dry and protected against damage from
weather, direct sunlight, surface contamination,
corrosion, construction traffic and other causes. Neatly
stack gypsum base flat to prevent sagging.


A. Environmental Requirements:

1. General: Establish and maintain environmental
conditions for application of veneer plaster to
comply with ASTM C843 and with veneer plaster
manufacturer's recommendations.

2. Minimum Room Temperatures: For adhesive attachment
of gypsum base and application of veneer plaster,
maintain not less than 50 degrees F. (10 degrees
C.) nor more than 80 degrees F. (27 degrees C.) for
one week prior to application and continuously
thereafter until veneer plaster has fully dried.
Distribute heat evenly; prevent concentrated or
uneven heat on veneer plaster near heat source.

3. Ventilate building spaces to remove water not
required for hydration of veneer plaster materials.
Avoid conditions which result in veneer plaster
drying too rapidly.



A. Georgia Pacific Corp.

B. National Gypsum Co.
Gold Bond Building Products Division

C. USG Corporation


A. Gypsum Board Products:

1. General: Provide gypsum boards of type indicated
in maximum lengths available to minimize end-to-end

2. Gypsum Base for Veneer Plaster: ASTM C588, of
types and thicknesses indicated below; with square
or tapered long edges as standard with
manufacturer; and as follows:

a. Type: Type X for fire-resistance-rated

b. Thickness: 5/8" unless otherwise indicated.

3. Gypsum Backing Board for Multi-Layer Applications:
Gypsum backing board, ASTM C442; or gypsum base,
ASTM C588; or gypsum wallboard, ASTM C36, as
recommended by manufacturer for application method
indicated; and as follows:

a. Type: Type X for fire-resistance-rated

b. Thickness: 5/8" unless otherwise indicated.

B. Joint Reinforcing Materials:

1. General: Provide joint reinforcing materials
indicated which comply with joint strength
requirements of ASTM C587 and are acceptable to
veneer plaster manufacturer for application

2. Joint Tape: Paper.

3. Joint Tape: Open-weave glass fiber fabric.

4. Embedding Material for Joint Tape: As recommended
by veneer plaster manufacturer for use with joint
tape material indicated.
1. For high strength veneer plaster and paper
tape, use setting-type joint compound.

C. Veneer Plaster Materials:

1. One-Component Regular Veneer Plaster: ASTM C587,
manufacturer's standard one-component veneer
plaster for application directly over the following
without use of separate base coat material such as
Dens-Cote (Georgia Pacific Corp.), Gold BondUni-Kal
Plaster (Gold Bond Building Products Div.,
National Gypsum Co.), Diamond Veneer Finish
(USG Corp.), or approved equal.

2. Two-Coat Veneer Plaster: Veneer plaster shall be
by the same manufacturer as the gypsum base where
installed over gypsum base conforming to ASTM C587,
such as Imperial Basecoat and Imperial Veneer Finish
Coat (USG Corp.), Gold Bond Kal-Kote Base Coat Veneer
Plaster and Uni-Kal Veneer Plaster(Gold Bond
Building Products Div., National Gypsum Co.), or
approved equal.

3. Finish Coat Aggregate: As required to match
adjacent surface.

D. Miscellaneous Materials:

1. General: Provide auxiliary materials for veneer
plaster construction which comply with referenced
standards and the recommendations of veneer plaster

2. Bonding Compound for Interior Plastering: ASTM

3. Laminating Adhesive: Special adhesive recommended
for laminating gypsum base face layers to base
layers of gypsum board in multiple-layer

4. Spot Grout: ASTM C475, setting-type joint compound
of type recommended for spot grouting hollow metal
door frames.

5. Gypsum Base Screws: ASTM C1002.

6. Concealed Acoustical Sealant: Non-drying, non-
hardening, non-skinning, non-staining, non-
bleeding, gunnable sealant such as
"Sheetrock Brand Acoustical Sealant"
(USG Corp.), or approved equal.

7. Sound Attenuation Blankets: Unfaced mineral fiber
blanket insulation produced by combining mineral
fibers of type described below with thermosetting
resins to comply with ASTM C665 for Type I
(blankets without membrane facing) such as
"Thermafiber SAFB (sound attenuation fire blankets), or approved equal.

1. Mineral Fiber Type: Fibers manufactured from
glass or slag.

2. Insulation shall have a flame spread rating of
15 or less with a smoke developed of 0 when
tested per ASTM E84.


A. Trim Accessories:

1. Provide cornerbeads, edge trim and control joints
of material and, for edge trim, shapes indicated
below which comply with ASTM C1047 and veneer
plaster manufacturer's recommendations for
application indicated.

2. Material: Formed metal or metal combined with
paper; with metal complying with the requirement;
sheet steel coated with zinc by hot-dip or
electrolytic processes, or with aluminum.

2.04 MIXES

A. Veneer Plaster Mixes: Mechanically mix veneer plaster
materials to comply with referenced veneer plaster
application standard and with recommendations of veneer
plaster manufacturer.



A. Examine substrates which veneer plaster construction
attaches to or abuts including preset hollow metal
frames, cast-in-anchors, and structural framing, with
installer present, for compliance with requirements for
installation tolerances and other conditions affecting
performance of veneer plaster construction. Do not
proceed with installation until unsatisfactory conditions
have been corrected.


A. Application of Gypsum Base, General:

1. Gypsum Base Application Standard: Comply with ASTM

2. Apply gypsum base to framing in accordance with
ASTM C844. Apply base with long dimension
parallel to studs and attach with 1 inch Type S
screws, spaced 8 inches on center around the
perimeter and 12 inches on center on the
intermediate stud. Do not force boards in place;
stagger end joints of adjoining boards. All
butting ends and edges of base shall occur over

3. Erection Tolerance: No more than 1/16 inch offsets
between planes of gypsum base faces, and 1/8 inch
in 8'-0" for plumb, level, warp and bow.

4. Install sound attenuation blankets as indicated,
prior to gypsum base unless readily installed after
base has been installed.

5. Locate exposed end-butt joints as far from center
of walls and ceilings as possible, and stagger not
less than 24 inches in alternate courses of base.

6. Install gypsum base for walls/partitions in manner
which minimizes the number of end-butt joints or
avoids them entirely where possible. At stairwells
and similar high walls, install gypsum base
horizontally with end joints staggered over studs.

7. Install gypsum base with face side out. Do not
install imperfect, damaged or damp boards. Butt
boards together for a light contact at edges and
ends with not more than 1/16 inch open space
between boards. Do not force into place.

8. Attach gypsum base to steel studs so that leading
edge or end of each board is attached to open
(unsupported) edge of stud flange first.

9. Attach gypsum base to supplementary framing and
blocking provided for additional support at
openings and cutouts.

10. Spot-grout hollow metal door frames for solid core
wood doors, hollow metal doors and doors over 32
inches wide. Apply spot-grout at each jamb anchor
clip just before inserting gypsum base into frame.

11. Form control and expansion joints in veneer plaster
surfaces at locations indicated, with space between
edges of gypsum base, prepared to receive trim

12. Cover both faces of steel stud partition framing
with gypsum base in concealed spaces (above
ceilings, etc.), except in chase walls which are
properly braced internally.

a. Except where concealed application is required
for sound, fire, air or smoke ratings,
coverage may be accomplished with scraps of
not less than 8 sq. ft. area, and may be
limited to not less than 75% of full coverage.

b. Fit gypsum base around ducts, pipes, and

13. Isolate perimeter of non-load-bearing veneer
plaster partitions at structural abutments.
Provide 1/4 inch to 1/2 inch space and trim edge with
"U" bead edge trim. Seal joints with acoustical

14. Where sound-rated veneer plaster construction is
indicated, including double-layer work and work on
resilient furring, seal construction at perimeters,
control and expansion joints, openings and
penetrations with a continuous bead of acoustical
sealant including a bead at both faces of
partitions. Comply with ASTM C919 and
manufacturer's recommendations for locations of
edge trim, and close off sound flanking paths
around or through construction including sealing of
partitions above acoustical ceilings.

15. Space fasteners in application of gypsum base to
comply with referenced gypsum base application
standard and manufacturer's recommendations.

B. Methods of Gypsum Base Application:

1. Single-Layer Application: Install gypsum base as

a. On partitions/walls apply gypsum base
vertically (parallel to framing), unless
otherwise indicated, and provide sheet lengths
which minimize end joints.

b. On partitions/walls 8'-1" or less in height
apply gypsum base horizontally (perpendicular
to framing); use maximum length sheets
possible to minimize end joints.

c. Fasten with screws.

2. Double-Layer Application: Install gypsum backing
board for base layer and gypsum base for face layer
as follows:

a. On partitions/walls apply base layer and face
layers vertically (parallel to framing) with
joints of base layer over supports and face
layer joints offset at least 10 inches with
base layer joints.

b. Fasten base layers with screws and face layer
with adhesive and supplementary fasteners.

C. Installation of Trim:

1. General: Where feasible, use same fasteners to
anchor trim accessory flanges as required to fasten
gypsum base to supports. Otherwise, fasten flanges
to comply with veneer plaster manufacturer's

2. Install corner beads at external corners.

3. Install metal edge trim where edge of gypsum base
would otherwise be exposed or semi-exposed.
Provide type with face flange to receive joint

a. Install bead where veneer plaster construction
is tightly abutted to other construction.

4. Install metal corner beads at external corners of
veneer plaster work.

5. Install control joints at locations indicated, or
if not otherwise indicated, at spacings and
locations required by referenced gypsum base
application standard.

D. Installation of Joint Reinforcement:

1. Reinforce interior angles and flat joints in gypsum
base with joint tape and embedding material to
comply with referenced gypsum veneer plaster
application standard and with veneer plaster
manufacturer's recommendations.

E. Veneer Plastering:

1. Gypsum Veneer Plaster Application General:

a. Plasterer shall be responsible for determining
the most effective procedure for curing and
time lapse between coats based on job
conditions. Plaster which is cracked or
crazed due to improper timing, curing or any
other reason shall not be accepted. Remove
and replace unacceptable plaster, including
gypsum base and bonding agent if damaged
during removal of defective plaster.

b. Gypsum Veneer Plaster Application Standard:
Apply gypsum veneer plaster to comply with
ASTM C843 and veneer plaster manufacturer's

2. Grout frames solidly and continuously where
indicated or required for fire-resistance ratings;
otherwise spot-grout at each anchorage point by
encasement of anchor devices in plaster grout.

3. Concealed Surfaces: Omit veneer plaster in areas
where plaster will be concealed from view in
completed work, but do not omit veneer plaster
behind cabinets, furniture, furnishings and similar
removable items.

4. Provide smooth-trowel finish, unless otherwise
indicated to match existing adjacent surfaces.

5. Provide texture finish matching existing, in
locations indicated.

6. For Two-Coat Applications:

a. Base Coat Application: Fill metal trim and
joint tape with tight, thin coat of base coat
plaster material. Allow to set before
proceeding with work. After bed has set up,
scratch in a tight, thin coat of basecoat
plaster over entire area, immediately doubling
back with plaster from same batch to full
thickness of 1/16 inch. Fill voids and
imperfections. Leave surface rough or cross-
rake with fine wire rake. Allow basecoat to
set to provide proper suction for finish coat.

b. Finish Coat Application: Scratch-in and
double back with finish plaster to fill out to
a smooth, dense surface, free from "cat faces"
and other irregularities or blemishes. Final
trowel after surface has become firm, holding
trowel flat and using water sparingly. Do not
overtrowel. Overall veneer plaster thickness
shall be 1/8 inch.

7. Grounds: Where frames and other units in the
veneer plastering act as grounds (not including
trim accessories) for flush plastering, groove
finish coat at juncture with the other work.


A. Remove temporary coverings used to protect other work.

B. Remove plaster spillage promptly from door frames,
windows and other adjoining work. Repair surfaces which
have been damaged by plastering work.

C. Patching: Cut out broken and damaged plaster to straight
lines. Cut out cracks to width of not less than one
inch. Fill areas to be patched with base material.
Apply finish coat of same material; patched area shall
match adjoining work.


A. Provide final protection and maintain conditions, in a
manner suitable to installer, which ensures veneer
plaster work being without damage or deterioration at
time of substantial completion.