Lathing and Plastering Walls and Ceilings

Procedure code:
920003S
Source:
Jacob Weinberger Us Courthouse, San Diego, Ca - Hallenbeck..
Division:
Finishes
Section:
Lath & Plaster
Last Modified:
07/20/2016

PART 1---GENERAL
1.01 SUMMARY

  1. This procedure includes guidance on re-lathing and re-plastering large surface areas with gypsum or Portland cement plaster. GENERALLY, THIS WORK SHOULD BE PERFORMED BY AN EXPERIENCED CONTRACTOR.
  2. 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 finishes.
    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.
  3. 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).

1.02 REFERENCES

    1. Lath and Plaster Standard: Comply with the Lath and Plaster Institute standards for application and finishing of Lath and Plaster, unless otherwise indicated.
    2. American Society for Testing and Materials (ASTM) [a nongovernment website]
    3. American National Standards Institute, Inc. (ANSI) [a nongovernment website]

1.03 SUBMITTALS

    1. 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.
    2. 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.
    3. 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 andarchitect of each project.
    4. 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.

1.04 QUALITY ASSURANCE

  1. 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.
    2. Coordination of Work: Coordinate layout and installation of suspension system components for suspended ceilings with other work supported by, or penetrating through, ceiling.
  2. 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.

1.05 DELIVERY, STORAGE AND HANDLING

    1. Packing and Shipping: Deliver materials in original packages, containers or bundles bearing brand name and identification of manufacturer.
    2. 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 deformation.
      2. Handle gypsum lath to prevent damage to edges, ends or surfaces. Protect metal corner beads and trim from being bent or damaged.

1.06 PROJECT/SITE CONDITIONS

  1. Environmental Requirements: Comply with referenced standards.
    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.

PART 2---PRODUCTS
2.01 MANUFACTURERS

  1. For Metal Supports:
    1. Bostik [a nongovernment website]
      11320 W. Watertown Plank Rd
      Wauwatosa, WI 53226
    2. Rockfon [a nongovernment website]
      4849 S. Austin Ave.
      Chicago, IL 60638
      (800) 323-7164
    3. National Gypsum Company [a nongovernment website]
      2001 Rexford Road Charlotte
      North Carolina 28211
      (704) 365-7300
    4. USG Corporation [a nongovernment website]
      550 West Adams St.
      Chicago, IL 60661
      800) 950-3839
  2. For Expanded Metal Lath:
    1. Bostik
    2. National Gypsum Company
    3. USG Corporation
  3. For Accessories:
    1. Fry Reglet Corporation [a nongovernment website]
      12342 Hawkins St.
      Santa Fe Springs, CA 90670
      sales@fryreglet.com
    2. National Gypsum Company
    3. Metalex Corporation [a nongovernment website]
      700 Liberty Drive
      Libertyville, IL 60048
      (847) 362-5400
    4. MM Systems Corporation [a nongovernment website]
      50 MM Way
      P.O. Box 98
      Pendergrass, GA 30567
      (800) 241-3460
    5. Plastic Components, Inc. [a nongovernment website]
      9051 NW 97 Terrace
      Miami, Florida 33178
      (800) 327-7077
    6. U.S Gypsum Association [a nongovernment website]
      810 First Street NE, #510
      Washington, DC 20002
      (202) 289-5440
  4. For Gypsum Lath and Plasters:
    1. National Gypsum Co.
    2. USG Corporation

2.02 MATERIALS

    1. 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).
    2. Vertical Metal Furring
    3. 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:
        1. Diamond Mesh Lath: Comply with the following requirements:
          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.
        2. Rib Lath: Comply with the following requirements:
          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, I Type: Plain, unless otherwise indicated.
        1. Type: Plain, unless otherwise indicated.
        2. Type: Type X for fire-resistance rated assemblies and where indicated.
        3. Thickness: 1/2", unless otherwise indicated.
      3. Lath Attachment Devices: Devices of material and type required by referenced standards and recommended by manufactugypsum lath to steel at locations indicated.
    4. Gypsum Plaster Materials:
      1. General:
        1. 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.Finish Coat Plasters: Types as indicated below:
          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.
        2. Finishing Hydrated Limes: ASTM C206; type N, normal hydrated lime for finishing purposes.
        3. Aggregates for Base Coat Plasters: ASTM C35;
        4. sand aggregate, unless otherwise indicated.
        5. 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 approved equal.
      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 equal.
      5. Finishing Hydrated Limes, Type N such as Red Top Gauging Plaster, USG Gypsum Plaster Finish Coat Plaster (USG Corp.), or approved equal.
    5. 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.
    6. 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.

2.03 ACCESSORIES

  1. Plaster Accessories for Gypsum Plaster:
  1. General: Comply with material provisions of ASTM C841; coordinate depth of accessories with thicknesses and number fabricated from zinc-coated (galvanized) steel.
  2. Metal Corner Beads: Type as indicated below, fabricated from zinc-coated (galvanized) steel.
    1. Type: Small nose with expanded flanges, unless otherwise indicated.
    2. Type: Small nose with expanded flanges, unless otherwise indicated.
    3. 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 forms:
    1. Cornerite: Strips pre-bent lengthwise in center for internal plaster angles not otherwise reinforced by metal lath lapped or carried around.
    2. 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:
    1. Material: Zinc-coated (galvanized) steel.
    2. One-Piece Type: Folded pair of non-perforated screeds in M-shaped configuration, with expanded or perforated flanges.
    3. 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.
  7. 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:
      1. Material: Zinc-coated (galvanized) steel.
      2. One-Piece Type: Folded pair of non-perforated screeds in M-shaped configuration, with expanded flanges.
      3. 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

    1. 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 below:

      a. Three-Coat Work Over Metal Lath: Base coats,
      as indicated below:
      1. Scratch Coat: High-strength gypsum gauging plaster with job-mixed sand.
        1. Brown Coat: High-strength gypsum gauging plaster with job-mixed sand.-Coat Work Over Unit Masonry: Base coats, as indicated below:
        2. 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.
      1. Troweled Finishes: Finish coat as indicated below:
        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 plaster.
        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 lime.
        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.
    3. 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 indicated.
      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 workability.
        1. 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.
        2. 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,
            -or-
          2. Base Coats: 1 part masonry cement, 3 to 4 parts sand.
        3. 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 workability.
      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 requirements:
        1. 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 manufacturers directions.
    4. Mixing:
      1. Mechanically mix cementitious and aggregate materials for plasters to comply with applicable referenced application standard and with recommendations of plaster manufacturer.

PART 3---EXECUTION
3.01 EXAMINATION

    1. 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.

3.02 PREPARATION

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

3.03 ERECTION, INSTALLATION, APPLICATION

  1. 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.
    3. 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.
    4. 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.
    5. Frame both sides of control and expansion joints independently, and do not bridge joints with furring and lathing or accessories.
  2. 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:
      1. For non-load (axial) bearing stud systems, comply with ASTM C754.
      2. For loadbearing (axial and transverse) stud systems, comply with ASTM C1007 and as
        indicated.
    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:
      1. 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.
  3. 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 indicated.
    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:
      1. 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- 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 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.
  4. 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 standards.
      1. Suspended and furred ceilings; minimum weight of diamond mesh lath, 3.4 lbs. per square yard (see 09210-02-R).
      2. Vertical metal framing and furring.
      3. Ceramic tile setting beds; use diamond mesh lath, 3.4 lbs. per square yard.
      4. Exterior sheathed wall surfaces; minimum weight of self-furring diamond mesh lath, 3.4 lbs. per square yard.
      5. Solid partitions.
      6. Monolithic surfaces not complying with requirements of referenced plaster application standards for characteristics which permit direct bond with plaster.
  5. Gypsum Lathing:
    1. Install gypsum lath for the following applications using attachment method indicated where plaster base coats are required.
      1. 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:
      1. With screws, or
      2. With clips, supplemented by screws where required by lath manufacturer.
      3. Where sound-rated partitions are indicated, attach lath with resilient clips.
  6. Installation of Plastering Accessories:
    1. General: Comply with referenced lathing and furring installation standards for provision and indicated for location:

END OF SECTION

Last Reviewed 2016-07-20