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Historic Preservation - Technical Procedures


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

Procedure code:



Federal Building/Uspo, Spokane, Wa - Gsa/Pbs




Veneer Plaster

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




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

         1.   Steel framing members to recei= ve 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 Precaution= s

         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-re= sistance-rated assemblies
                   ident= ical to those indicated by design
                   desig= nations in U.L. "Fire Resistance
                   Direc= tory" or in listing of other testing and
                   agenc= ies acceptable to authorities having
                   juris= diction.


    A.   Product Data:  Submit manufacturer's product<= br>          specifications and installation instruct= ions for each
         veneer plaster and gypsum basecoat compo= nent, 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 manufa= cturer 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 suppli= er.

    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 contam= ination,
         corrosion, construction traffic and other causes.  Neatly
         stack gypsum base flat to prevent saggin= g.


    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 recommenda= tions.

         2.   Minimum Room Temperatures:  For adhesive attachment
              of gypsum base and applic= ation 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 applica= tion 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.
         Commercial Division (Gypsum)
         133 Peachtree St. NE
         Atlanta, GA  30303
         800/225-6119 or 404/652-5683

    B.   National Gypsum Co.
         Gold Bond Building Products Division
         2001 Rexford Rd.
         Charlotte, NC  28211

    C.   Tremco, Inc.
         3735 Green Rd.
         Beachwood, OH  44122

    D.   U.S. Gypsum Association
         810 First Street NE, #510
         Washington, DC  20002
         202/289-5440, FAX 202/289-3707


    A.   Gypsum Board Products:

         1.   General:  Provide gypsum boards of type indicated
              in maximum lengths availa= ble 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
                   assem= blies.

              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 manufactur= er for application method
              indicated; and as follows= :

              a.   Type:  Type X for fire-resistance-rated
                   assem= blies.

              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 manufactur= er 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 manufac= turer for use with joint
              tape material indicated.<= br>
              1.   For high streng= th 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  (Ge= orgia Pacific Corp.),  Uni-Kal
              Plaster  (Gold Bond Building Products Div.,
              National Gypsum Co.),  Diamond Interior Finish
              (U.S. Gypsum Association), 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 Finish
              Coat  (U.S. Gypsum Association),  Kal-Kote Base
              Plaster  and  U= ni-Kal Finish Coat  (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 auxilia= ry materials for veneer
              plaster construction which comply with referenced
              standards and the recomme= ndations of veneer plaster

         2.   Bonding Compound for Interior Plastering:  ASTM

         3.   Laminating Adhesive:  Spe= cial 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 "Acoustical
              Sealant" (Tremco), "Acoustical Sealant" (U.S.
              Gypsum Association), or approved equal.

         7.   Sound Attenuation Blankets:  Unfaced mineral fiber
              blanket insulation produc= ed 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&qu= ot;, Manville "Pyro-Fiber Sound
              Control Blankets", (U.S. Interiors, Inc., U.S.
              Gypsum Association), 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 complyi= ng 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 recommenda= tions of veneer
         plaster manufacturer.



    A.   Examine substrates which veneer plaster constructi= on
         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 condit= ions affecting
         performance of veneer plaster constructi= on.  Do not
         proceed with installation until unsatisf= actory conditions
         have been corrected.


    A.   Application of Gypsum Base, General:

         1.   Gypsum Base Application Standa= rd:  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.<= br>
         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 suppleme= ntary 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 conce= aled spaces (above
              ceilings, etc.), except in chase walls which are
              properly braced internall= y.

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

              b.   Fit gypsum base around ducts, pipes, and
                   condu= its.

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

         14.  Where sound-rated veneer plast= er 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 conti= nuous bead of acoustical
              sealant including a bead at both faces of
              partitions.  Comply with ASTM C919 and
              manufacturer's recommenda= tions for locations of
              edge trim, and close off sound flanking paths
              around or through constru= ction including sealing of
              partitions above acoustic= al 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/w= alls apply gypsum base
                   verti= cally (parallel to framing), unless
                   other= wise indicated, and provide sheet lengths
                   which minimize end joints.

              b.   On partitions/w= alls 8'-1" or less in height
                   apply gypsum base horizontally (perpendicular
                   to framing); use maximum length sheets
                   possi= ble 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/w= alls 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 extern= al 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 indicate= d, 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 recommenda= tions.

    E.   Veneer Plastering:

         1.   Gypsum Veneer Plaster Applicat= ion General:

              a.   Plasterer shall be responsible for determining
                   the most effective procedure for curing and
                   time lapse between coats based on job
                   condi= tions.  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
                   direc= tions.

         2.   Grout frames solidly and conti= nuously 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, furnitur= e, furnishings and similar
              removable items.

         4.   Provide smooth-trowel finish, unless otherwise
              indicated to match existi= ng adjacent surfaces.

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

         6.   For Two-Coat Applications:

              a.   Base Coat Appli= cation:  Fill metal trim and
                   joint tape with tight, thin coat of base coat
                   plast= er material.  Allow to set before
                   proce= eding with work.  After bed has set up,
                   scrat= ch in a tight, thin coat of basecoat
                   plast= er over entire area, immediately doubling
                   back with plaster from same batch to full
                   thick= ness of 1/16 inch.  Fill voids and
                   imper= fections.  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
                   overt= rowel.  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.

                             END OF SECTION