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Historic Preservation - Technical Procedures

Spectitle:

Patching Large Holes In Plaster With Sheetrock

Procedure code:

0920012R

Source:

Developed For Hspg (Nps - Sero)

Division:

Finishes

Section:

Lath & Plaster

Last Modified:

02/24/2012

Details:

Patching Large Holes In Plaster With Sheetrock



PATCHING LARGE HOLES IN PLASTER WITH SHEETROCK


PART 1---GENERAL

1.01 SUMMARY

    A.   This procedure includes guidance on patching holes in
         wall plaster larger than 4 inches in diameter.  When
         large sections of plaster are missing, drywall patches
         can be used as a base.

    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).


PART 2---PRODUCTS

2.01 MATERIALS

    A.   Drywall and joint compound

    B.   Nails and screws

    C.   Joint tape (cloth mesh preferred)

2.02 EQUIPMENT

    A.   6 inch taping knife

    B.   12 inch taping knife

    C.   Float

    D.   Hawk

    E.   Sanding sponge (medium fine grit)

    F.   Stiff putty knife

    G.   Goggles, work gloves, and dust mask

    H.   Hammer and cold chisel

    I.   Needlenose pliers and wire cutter

    J.   Screwgun and drill
   
    K.   Spray bottle and drop cloths

    L.   Tin snips

    M.   Vacuum


PART 3---EXECUTION

3.01 EXAMINATION

    A.   Determine the extent of damaged plaster.  Look for:

         1.   Holes.

         2.   Water Stains:  Brownish rings on the plaster,
              especially the ceilings, indicate that the plaster
              has been wet.  If the water was stopped quickly,
              the surface may only need to be sealed with
              pigmented shellac to prevent the stain from
              bleeding through the new paint or wallpaper.
              However, if the leak continued for a long period,
              the plaster may need to be replaced, and will often
              have a powdery appearance.

         3.   Chipping, flaking and delamination of plaster due
              to water infiltration.

3.02 ERECTION/INSTALLATION/APPLICATION

    A.   Removing Deteriorated Plaster:

         1.   Wear a dust mask, goggles and gloves and pull loose
              plaster from the walls with your hands (a flat
              prybar may also be helpful in removing plaster that
              is difficult to remove by hand).

         2.   To remove sound plaster, for whatever reason, drill
              holes in the line of your cut with a carbide drill
              bit; Holding the chisel at a shallow angle,
              carefully cut directly from hole to hole with a
              cold chisel; Cut the resulting plaster free from
              the lath by chipping the keys from the side.

         3.   Cut the plaster back to the nearest studs to make a
              regular opening, and re-secure the lath with
              drywall nails.

         4.   Use plaster washers and wood screws to re-secure
              weakly-keyed areas of sound plaster to the wall or
              ceiling.

         5.   Knock any plaster stuck between the lath back into
              the wall cavity.

         6.   Vacuum all dust, loose plaster, and other debris
              from the hole with a shop-vac, or sweep it out with
              an old paintbrush.

    B.   Making a Sheetrock Patch:

         1.   Shim the Sheetrock as required to bring it up flush
              with the surface of the adjacent plaster.

         2.   Cut a Sheetrock patch to fit neatly in the opening.

         3.   Nail or screw the sheetrock in place; Nailheads or
              screwheads should be set slightly below the surface
              of the Sheetrock, but without breaking the paper.

         4.   Using the 6 inch taping knife, fill the joint
              between the Sheetrock and the plaster with a small
              amount of joint compound.

         5.   Apply a fairly smooth, heavy coat of compound over
              the joint a little wider than the tape width.

         6.   Center the joint tape over the length of the joint;
              Hold the 6 inch taping knife at a 45 degree angle
              and press the tape into the compound; Smooth out
              any air pockets under the tape.

         7.   Apply a thin layer of compound over the tape and
              apply a first coat of compound to nails or screws.

         8.   Knock off any ridges or pimples that develop from
              shrinkage and cracking in the compound.

         9.   Apply the second coat of compound with the 6 inch
              taping knife and feather the edges out 6-8 inches;
              Scrape off any ridges or bumps.

         10.  When the second coat is dry, apply the third coat
              of compound with the 12 inch taping knife and
              feather the edges out 12-14 inches.

         11.  Touch up low spots with additional compound or high
              spots by light sanding with a wet sanding sponge.

                             END OF SECTION