Historic Preservation - Technical Procedures

Guidelines For Lathing And Plastering Walls And Ceilings
Procedure code:
Jacob Weinberger Us Courthouse, San Diego, Ca - Hallenbeck..
Lath & Plaster
Last Modified:
Guidelines For Lathing And Plastering Walls And Ceilings
Last Modified:




    A.   This procedure includes guidance on relathing and
         replastering large surface areas with gypsum or portland

    B.   Restoration:  The work required includes finish
         restoration of original surfaces to the greatest degree
         possible, while complying with current codes and
         construction limitations.

         1.   The contractor is to provide all necessary systems
              and materials as required to produce the intended

         2.   Where current codes cannot be complied with, and/or
              construction limitations (including deterioration
              of existing substrate) are such that the intended
              finish cannot be achieved, notify the architect for
              clarification and/or decision prior to proceeding
              with the work.

    C.   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.   Lath and Plaster Standard:  Comply with the Lath and
         Plaster Institute standards for application and finishing
         of Lath and Plaster, unless otherwise indicated.

    B.   American Society for Testing and Materials (ASTM)

    C.   American National Standards Institute, Inc. (ANSI)


    A.   Product Data:  Submit manufacturer's product
         specifications and installation instructions for each
         material, including other data as may be required to show
         compliance with these specifications.

    B.   Submit samples to the architect, 12" by 12" in size of
         finishes for approval.  Approved sample shall become the
         standard of comparison for all cement plaster work.

    C.   Restoration:  The restoration contractor must supply
         proof of work on this type of project by submitting a
         list of pertinent projects the applicator has worked on
         which includes the scope of work, the budget for the
         scope of work, and a way to contact the owner and
         architect of each project.

    D.   Restoration:  Restore 20 square feet of each type of
         plaster wall, ceiling, or trim for review by architect
         before restoring all plaster.  Where new plaster must be
         installed to match existing to repair damaged areas,
         install 20 square feet in its final location for review
         by architect.


    A.   Fire-Resistance Rating:  Where plastered assemblies with
         fire-resistance ratings are indicated or are required to
         comply with governing regulations, provide materials and
         installations identical with applicable assemblies which
         have been tested and listed by recognized authorities
         including UL.

         1.   Provide plaster having the same aggregate as
              specified for similar non-rated work, unless
              specified aggregate has not been tested and
              approved by UL for the required rating.

    B.   Coordination of Work:  Coordinate layout and installation
         of suspension system components for suspended ceilings
         with other work supported by, or penetrating through,

    C.   Field Construction Mock-Up:  Prior to installation of
         interior plaster work, fabricate mock-up panels for each
         type of finish and application required using materials,
         including lath and support system, in location indicated,
         or if not otherwise indicated, as directed by RHPO.
         Demonstrate the proposed range of color, texture and
         workmanship to be expected in complete work.  Obtain
         RHPO's acceptance of panel's visual quality before start
         of work.  Retain panel during construction as a standard
         for judging completed work.


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

    B.   Storage and Protection:  

         1.   Store materials inside, under cover and in manner
              to keep them dry, protected from weather, direct
              sunlight, surface contamination, aging, corrosion,
              and damage from construction traffic and other
              causes.  Neatly stack gypsum lath flat to prevent

         2.   Handle gypsum lath to prevent damage to edges, ends
              or surfaces.  Protect metal corner beads and trim
              from being bent or damaged.


    A.   Environmental Requirements:  Comply with referenced

         1.   Cold Weather Protection:  When ambient outdoor
              temperatures are below 55 degrees F. (13 degrees
              C.) nor more than 70 degrees F. (21 degrees C.) for
              not less than 1 week prior to beginning plaster
              application, during its application, and until
              plaster is dry but for not less than one week after
              application is complete.  Distribute heat evenly;
              prevent concentrated or uneven heat from contacting
              plaster near heat source.

         2.   Ventilation:  Ventilate building spaces as required
              to remove water in excess of that required for
              hydration of plaster.  Begin ventilation
              immediately after plaster is applied and continue
              until it sets.

         3.   Protect contiguous work from soiling, spattering,
              moisture deterioration and other harmful effects
              which might result from plastering.



    A.   For Metal Supports:

         1.   Bostik

         2.   Chicago Metallic Corp.

         3.   National Gypsum Co.

         4.   USG Corporation           


    B.   For Expanded Metal Lath:

         1.   Bostik
         2.   National Gypsum Co.

         3.   USG Corporation 

    C.   For Accessories:

         1.   Fry Reglet Corp.

         2.   National Gypsum Co.
         3.   Metalex Corporation

         4.   MM Systems Corp.

         5.   Plastic Components, Inc.

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

    D.   For Gypsum Lath and Plasters:

         1.   National Gypsum Co.
         2.   USG Corporation 


    A.   Steel Studs and Runners/Tracks:

         1.   Non-Load (Axial) Bearing Studs and Runners:  ASTM
              C645 and complying with following requirements for
              minimum thickness of base metal (uncoated).

    B.   Vertical Metal Furring

    C.   Lath:

         1.   Expanded Metal Lath:  Fabricate expanded metal lath
              from uncoated or zinc-coated (galvanized) steel
              sheet to produce lath complying with ASTM C847 for
              type, configuration and other characteristics
              indicated below, with uncoated steel sheet painted
              after fabrication into lath:

              a.   Diamond Mesh Lath:  Comply with the following

                   1)   Configuration:  Flat; Weight:  3.4 lbs.
                        per square yard.

                   2)   Configuration:  Self-furring; Weight:
                        3.4 lbs. per square yard.

                   3)   Paper Backing:  Where paper-backed
                        diamond mesh lath is indicated, provide
                        asphalt-impregnated paper factory-bonded
                        to back and complying with FS UU-B-790,
                        for Type I, Grade D (vapor permeable),
                        Style 2.

              b.   Rib Lath:  Comply with the following

                   1)   Configuration:  Rib depth of 3/8";
                        Weight:  3.4 lbs. per square yard.

         2.   Gypsum Lath:  ASTM C37, type and thicknesses as
              indicated below, in length standard with
              manufacturer for thickness indicated.

              a.   Type:  Plain, unless otherwise indicated.

              b.   Type:  Type X for fire-resistance rated
                   assemblies and where indicated.

              c.   Thickness:  1/2", unless otherwise indicated.

         3.   Lath Attachment Devices:  Devices of material and
              type required by referenced standards and
              recommended by manufacturer for secure attachment
              of lath to framing members and of lath to lath.

              a.   Provide resilient clips for attachment of
                   gypsum lath to steel at locations indicated.

    D.   Gypsum Plaster Materials:

         1.   General:

              a.   Base Coat Plasters:  ASTM C28; high-strength
                   gypsum neat plaster with a minimum average dry
                   compressive strength of 2,800 psi per ASTM
                   C472 for a mix of 100 lbs. plaster and 2 cubic
                   feet of sand.

              b.   Finish Coat Plasters:  Types as indicated

                   1)   High-strength gypsum gauging plaster,
                        ASTM C28, with minimum average dry
                        compressive strength of 5,000 psi per
                        ASTM C472 for a neat mix.

                   2)   Gypsum Keene's cement, ASTM C61.

              c.   Finishing Hydrated Limes:  ASTM C206; type N,
                   normal hydrated lime for finishing purposes.

              d.   Aggregates for Base Coat Plasters:  ASTM C35;
                   sand aggregate, unless otherwise indicated.

              e.   Aggregates for Finish Coat Plaster with
                   Floated Finish:  ASTM C35; graded per ASTM
                   C842; sand aggregate.

         2.   Gypsum Gauging Plaster such as  Champion Quality White Gauging
              Plaster ,  Red Top Gypsum Plaster,  Gauging Plaster  (National Gypsum Co.), or aproved

         3.   High-Strength Gypsum Gauging Plaster such as
               Structo-Base Gypsum Plaster (USG Corp.), or
              approved equal.

         4.   Gypsum Keene's Cement such as  Red Top Keenes
              Cement  (USG Corp.), or approved

         5.   Finishing Hydrated Limes, Type N such as  Red Top
              Gauging Plaster, USG Gypsum Plaster Finish Coat Plaster

              (USG Corp.), or
              approved equal.

    E.   Portland Cement Plaster Materials:

         1.   Base Coat Cements:  Portland cement, ASTM C150,
              Type I or III.

         2.   Finish Coat Cement:  Portland cement, ASTM C150,
              Type I, white.

         3.   Lime:  Special hydrated lime for finishing
              purposes, ASTM C206, Type S, or special hydrated
              lime for masonry purposes, ASTM C207, Type S.

         4.   Sand Aggregate for Base Coats:  ASTM C897.

         5.   Aggregate for Finish Coats:  ASTM C897,
              manufactured or natural sand, white in color.

    F.   Miscellaneous Materials:

         1.   Water for Mixing and Finishing Plaster:  Drinkable,
              free of substances capable of affecting plaster set
              or of damaging plaster, lath or accessories.

         2.   Bonding Compound for Gypsum Plaster:  ASTM C631.


    A.   Plaster Accessories for Gypsum Plaster:

         1.   General:  Comply with material provisions of ASTM
              C841; coordinate depth of accessories with
              thicknesses and number of plaster coats required.

         2.   Metal Corner Beads:  Type as indicated below,
              fabricated from zinc-coated (galvanized) steel.

              a.   Type:  Small nose with expanded flanges,
                   unless otherwise indicated.

              b.   Type:  Small nose with perforated flanges, for
                   use on curved corners.

              c.   Type:  Small nose with expanded flanges
                   reinforced by perforated stiffening rib, for
                   use on columns and finishing masonry corners.

         3.   Strip Reinforcement:  Smooth edge strips of
              expanded metal lath fabricated from uncoated or
              zinc-coated (galvanized) steel sheet, with uncoated
              steel painted after fabrication; in the following

              a.   Cornerite:  Strips pre-bent lengthwise in
                   center for internal plaster angles not
                   otherwise reinforced by metal lath lapped or
                   carried around.

              b.   Stripite:  Flat strips for reinforcing joints
                   in gypsum lath, non-metallic bases, and
                   between dissimilar plaster bases.

         4.   Casing Beads:  Square-edged style, with short or
              expanded flanges to suit kinds of plaster bases
              indicated; of zinc-coated (galvanized) steel.

         5.   Curved Casing Beads:  Square-edged style,
              fabricated from aluminum coated with clear plastic,
              preformed into curve of radius indicated.

         6.   Control Joints:  Prefabricated, of material and
              type indicated below:

              a.   Material:  Zinc-coated (galvanized) steel.

              b.   One-Piece Type:  Folded pair of non-perforated
                   screeds in M-shaped configuration, with
                   expanded or perforated flanges.

              c.   Two-Piece Type:  Pair of casing beads with
                   back flanges formed to provide slip-joint
                   action, adjustable for joint widths from 1/8"
                   to 5/8".

                   1)   Provide removable protective tape on
                        plaster face of control joints.

    B.   Plaster Accessories for Portland Cement Plaster:

         1.   Metal Corner Reinforcement:  Expanded large mesh
              diamond mesh lath fabricated from zinc-alloy or
              welded wire mesh fabricated from 0.0475" diameter
              zinc-coated (galvanized) wire, and specially formed
              to reinforce external corners of portland cement
              plaster on exterior exposures while allowing full
              plaster encasement.

         2.   Metal Corner Beads:  Small nose corner beads
              fabricated from zinc alloy, with expanded flanges
              of large mesh diamond lath to allow full encasement
              by plaster.

         3.   Casing Beads:  Square-edged style, with expanded
              flanges and removable protective tape, of the zinc-
              coated (galvanized) steel.

         4.   Control Joints:  Prefabricated, of material and
              type indicated below:

              a.   Material:  Zinc-coated (galvanized) steel.

              b.   One-Piece Type:  Folded pair of non-perforated
                   screeds in M-shaped configuration, with
                   expanded flanges.

              c.   Two-Piece Type:  Pair of casing beads with
                   back flanges formed to provide slip joint
                   action, adjustable for joint widths from 1/8"
                   to 5/8".

2.04 MIXES

    A.   Gypsum Plaster Mixes and Compositions:

         1.   Plaster Base Coat Composition:  Comply with ASTM
              C842 and manufacturer's directions for gypsum
              plaster base coat proportions which correspond to
              application methods and plaster bases indicated

              a.   Three-Coat Work Over Metal Lath:  Base coats,
                   as indicated below:

                   1)   Scratch Coat:  High-strength gypsum
                        gauging plaster with job-mixed sand.

                   2)   Brown Coat:  High-strength gypsum gauging
                        plaster with job-mixed sand.

              b.   Two-Coat Work Over Unit Masonry:  Base coats,
                   as indicated below:

                   1)   Base Coats:  Gypsum neat plaster with
                        job-mixed sand.

         2.   Finish Coats:  Proportion materials in parts by dry
              weight for finish coats to comply with the
              following requirements for each type of finish coat
              and texture indicated.

              a.   Troweled Finishes:  Finish coat as indicated

                   1)   Gypsum Gauging Plaster:  1 part plaster
                        and 2 parts lime; Over lightweight
                        aggregate base coats, add 1/2 cubic feet
                        of perlite finish or 50 lbs. of No. 1
                        white silica sand per 100 lbs. of

                   2)   High-Strength Gypsum Gauging Plaster:  1
                        part plaster and 1 part lime.

                   3)   Gypsum Keene's Cement:  4 parts plaster
                        to 1 part lime; 2 parts plaster to 1 part

                   4)   Floated Finishes:  Gypsum gauging
                        plaster:  1 part plaster, 2 parts lime, 8
                        parts sand; Gypsum Keene's cement:  2
                        parts plaster, 1 part lime, 8 parts sand.

    B.   Portland Cement Plaster Mixes and Compositions:

         1.   General:  Comply with ASTM C926 for portland cement
              plaster base and finish coat mixes as applicable to
              plaster bases, materials and other requirements and

         2.   Portland Cement Plaster Base Coat Mixes and
              Compositions:  Proportion materials for respective
              base coats in parts by volume for cementitious
              materials and in parts by volume per sum of
              cementitious materials for aggregates to comply
              with the following requirements for each method of
              application and plaster base indicated.  Adjust mix
              proportions below within limits specified to attain

              a.   Three-Coat Work Over Metal Lath:  Base coats
                   as indicated below:

                   1)   Scratch Coat:  1 part portland cement, 0
                        to 3/4 parts lime, 2-1/2 to 4 parts sand.

                   2)   Brown Coat:  1 part portland cement, 0 to
                        3/4 parts lime, 3 to 5 parts sand.

              b.   Two-Coat Work Over Concrete Unit Masonry:
                   Base coats as indicated below:

                   1)   Base Coats:  1 part portland cement, 3/4
                        to 1-1/2 parts lime, 3 to 4 parts sand,

                   2)   Base Coats:  1 part masonry cement, 3 to
                        4 parts sand.

              c.   Fiber Content:  Add fiber to mixes above to
                   comply with fiber manufacturer's directions
                   but not to exceed 2 lbs. per cubic foot of
                   cementitious materials.  Reduce aggregate
                   quantities accordingly to maintain

         3.   Job-Mixed Portland Cement Plaster Finish Coats:
              Proportion materials for finish coats in parts by
              volume for cementitious materials and parts by
              volume per sum of cementitious materials for
              aggregates to comply with the following

              a.   1 part portland cement, 3/4 to 1-1/2 parts
                   lime, 3 parts sand.

         4.   Factory-Prepared Portland Cement Finish Coats:  Add
              water only; comply with finish coat manufacturer s

    C.   Mixing:

         1.   Mechanically mix cementitious and aggregate
              materials for plasters to comply with applicable
              referenced application standard and with
              recommendations of plaster manufacturer.



    A.   Perform a thorough examination of the existing conditions
         of plaster items.  Perform any necessary tests on an
         inconspicuous surface to determine the current conditions
         and appropriate steps and materials necessary for
         restoration of all existing plaster surfaces.


    A.   Surface Preparation: Clean plaster bases and substrates
         to be plastered, removing loose materials, coatings and
         other substances which might impair the work.


    A.   Installation of Lathing and Furring, General:

         1.   Interior Lathing and Furring Installation Standard:
              Install lathing and furring materials indicated for
              gypsum plaster to comply with ASTM C841.

         2.   Portland Cement Plaster Lathing and Furring
              Standard:  Install lathing and furring materials
              indicated for portland cement plaster to comply
              with ANSI A42.3.

         2.   Install supplementary framing, blocking, and
              bracing at terminations in the work and for support
              of fixtures, equipment services, heavy trim, and
              similar work to comply with details indicated or if
              not otherwise indicated, to comply with applicable
              published recommendations of gypsum plaster
              manufacturer, or if not available, of "Gypsum
              Construction Handbook" published by USG Corp.

         3.   Isolation:  Where lathing and metal support system
              abuts building structure horizontally, and where
              partition/wall work abuts overhead structure,
              isolate the work from structural movement
              sufficiently to prevent transfer of loading into
              the work from the building structure.  Install slip
              or cushion type joints to absorb deflections but
              maintain lateral support.

         4.   Frame both sides of control and expansion joints
              independently, and do not bridge joints with
              furring and lathing or accessories.

    B.   Installation of Metal Support System:

         1.   General:  Install components for steel stud
              wall/partition support systems to comply with
              directions of steel stud manufacturer for
              applications indicated and with the following:

              a.   For non-load (axial) bearing stud systems,
                   comply with ASTM C754.

              b.   For loadbearing (axial and transverse) stud
                   systems, comply with ASTM C1007 and as

         2.   Steel Stud Systems to Receive Metal Lath:  Comply
              with requirements of ML/SFA "Specifications for
              Metal Lathing and Furring" applicable to each
              installation condition and type of metal stud
              system indicated.

         3.   Wire Truss-Type Non-Load Bearing Stud Systems:
              Space studs not over 16" o.c.

         4.   Steel Stud Systems to Receive Gypsum Lath:  Space
              suds as follows:

              a.   For 1/2" thick gypsum lath; not over 24" o.c.

         5.   Extend and attach partition support systems to
              structure above suspended ceilings, unless
              otherwise indicated.

    C.   Installation of Vertical Metal Furring:

         1.   Metal Furring to Receive Metal Lath:  Comply with
              requirements of MS/SFA "Specification for Metal
              Lathing and Furring" applicable to each
              installation to each installation condition

         2.   Metal Furring to Receive Gypsum Lath:  Comply with
              referenced interior lathing and furring
              installation standard applicable to each
              installation condition indicated.  Space furring
              channels as follows:

              a.   For 1/2" thick gypsum lath; not over 24" o.c.

         3.   Z-Furring with Thermal Insulation:  Erect thermal
              insulation vertically and hold in place with Z-
              furring members spaced 24" o.c.  Except at external
              corners, securely attach narrow flanges of furring
              members to wall with concrete stub nails or power-
              drive fasteners spaced 24" o.c.  At external
              corners, attach wide flange of furring members to
              wall with short flange extending beyond corner; on
              adjacent wall surface, screw attach short flange of
              furring channel to web of attached channel.  Start
              from this furring channel with standard width
              insulation panel and continue in regular manner.
              At internal corners, space second member no more
              than 12" from corner and cut insulation to fit.
              Until plaster base is installed hold insulation in
              place with 10" staples fabricated from 18-gage tie
              wire and inserted through slot in web of member.

    D.   Metal Lathing:

         1.   Install expanded metal lath for the following
              applications where plaster base coats are required.
              Provide appropriate type, configuration and weight
              of metal lath selected from materials indicated
              which comply with referenced lathing installation

              a.   Suspended and furred ceilings; minimum weight
                   of diamond mesh lath, 3.4 lbs. per square yard
                   (see 09210-02-R).

              b.   Vertical metal framing and furring.

              c.   Ceramic tile setting beds; use diamond mesh
                   lath, 3.4 lbs. per square yard.

              d.   Exterior sheathed wall surfaces; minimum
                   weight of self-furring diamond mesh lath, 3.4
                   lbs. per square yard.

              e.   Solid partitions.

              f.   Monolithic surfaces not complying with
                   requirements of referenced plaster application
                   standards for characteristics which permit
                   direct bond with plaster.

    E.   Gypsum Lathing:

         1.   Install gypsum lath for the following applications
              using attachment method indicated where plaster
              base coats are required.

              a.   Wood framing and furring; attach lath to
                   framing with screws to comply with lath
                   manufacturer's directions; with nails.

         2.   Suspended and furred ceilings; attach lath to
              furring members with clips.

         3.   Vertical metal framing and furring; attach lath to
              framing as follows:

              a.   With screws, or

              b.   With clips, supplemented by screws where
                   required by lath manufacturer.

              c.   Where sound-rated partitions are indicated,
                   attach lath with resilient clips.

    F.   Installation of Plastering Accessories:

         1.   General:  Comply with referenced lathing and
              furring installation standards for provision and
              indicated for location:



Last Reviewed 2015-04-20