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Historic Preservation - Technical Procedures

Spectitle:
Patching Small Chips And Cracks In Plaster

Procedure code:
0921005R

Source:
Tacoma Union Station Courthouse/Tacoma, Wa - Gsa/Pbs

Division:
Finishes

Section:
Gypsum Plaster

Last Modified:
02/24/2012

Details:
Patching Small Chips And Cracks In Plaster



PATCHING SMALL CHIPS AND CRACKS IN PLASTER


PART 1---GENERAL

1.01  SUMMARY

     A.     This procedure includes guidance on patching small chips,
            cracks or depressions in plaster surfaces.

     B.     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).

     C.     For guidance on repairing hairline cracks, see 09210-02-
            R; for guidance on repairing large holes, see 09200-12-R
            and 09210-03-R.

1.02  REFERENCES

     A.     American National Standards Institute (ANSI) Standard
            Specifications:  ANSI, 1430 Broadway, New York, NY
            10018.

     B.     American Society for Testing and Materials (ASTM)
            Standard Specifications:  ASTM, 1916 Race Street,
            Philadelphia, PA  19103-1187, 215/299-5400.


PART 2---PRODUCTS

2.01  MANUFACTURERS

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

2.02  MATERIALS

     A.     Gypsum Plaster Materials:

            1.    General:  gypsum plastering materials shall conform
                  to ANSI A42.1.  Provide neat or ready-mixed
                  materials at installer's option unless indicated
                  otherwise.

            2.    Base coat plaster:  Perlite gypsum plaster such as
                  "Structo-Lite" (U.S. Gypsum Association), or
                  approved equal.

            3.    Base coat aggregate:  Sand.

            4.    Finish coat plaster:  Keene's cement.

            5.    Finishing lime:  Type is installer's option.

     B.     Bonding Materials:  Bonding agent shall conform to ASTM
            C631.

2.03  EQUIPMENT

     A.     Joint knife

     B.     Sponge or heavy-nap cloth

     C.     Crack widener or triangular can opener

     D.     Stiff bristle brushes

     E.     Hawk

     F.     Slicker (flexible straight-edge)

     G.     Plasterer's trowel

     H.     Margin trowel

     I.     Mortarboard and mudpan

     J.     Pointing trowel


PART 3---EXECUTION

3.01  ERECTION, INSTALLATION, APPLICATION

     A.     Scrape loose or damaged finish plaster and peeling paint
            from surface with chisel or joint knife.  Remove material
            where required to enlarge cracks, chips, holes, etc. to
            at least 1/2 inch across and undercut to improve bonding
            of new material.

     B.     Brush or vacuum surface to remove dust and debris.

     C.     Moisten the surface by lightly spraying a fine mist of
            clean water from a spray bottle.

     D.     Apply skim finish coat over low areas to bring entire
            finished surface out flush with the projecting firm and
            sound layers of adjacent plaster or paint.  Form plaster
            as required to match original configuration and design or
            ornamental plaster.

     E.     Once dry, sand by hand to produce a surface without
            bumps, cracks or depressions, ready to receive finish
            treatment.

3.02  ADJUSTING/CLEANING

     A.     Upon completion of this work, all floors, walls and other
            adjacent surfaces that are stained, marred, or otherwise
            damaged by work in this procedure shall be cleaned and
            repaired and all work and the adjacent areas shall be
            left in a clean and perfect condition.

     B.     All completed work shall be adequately protected from
            damage by subsequent building operations and effects of
            weather.  Protection shall be by methods recommended by
            the manufacturer of installed materials and as approved
            by the RHPO.

                                 END OF SECTION