U.S. General Services Administration
Technical Procedures Disclaimer
Prior to inclusion in GSA’s library of procedures, documents are reviewed by one or more qualified preservation specialists for general consistency with the Secretary of Interior Standards for rehabilitating historic buildings as understood at the time the procedure is added to the library. All specifications require project-specific editing and professional judgement regarding the applicability of a procedure to a particular building, project or location. References to products and suppliers are to serve as a general guideline and do not constitute a federal endorsement or determination that a product or method is the best or most current alternative, remains available, or is compliant with current environmental regulations and safety standards. The library of procedures is intended to serve as a resource, not a substitute, for specification development by a qualified preservation professional.
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We’ve reviewed these procedures for general consistency with federal standards for rehabilitating historic buildings and provide them only as a reference. Specifications should only be applied under the guidance of a qualified preservation professional who can assess the applicability of a procedure to a particular building, project or location. References to products and suppliers serve as general guidelines and do not constitute a federal endorsement nor a determination that a product or method is the best alternative or compliant with current environmental regulations and safety standards.
(NOTE: various names are used for the same manufactured product including: drywall, plasterboard, wall board, gypsum board, and there there are further names for modified drywall and proprietary products with trademarked names)
PART 1–GENERAL
1.01 SUMMARY
- 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.
- See 01100-07-S for general project guidelines to be reviewed along with this procedure. These guidelines cover the following sections:
- Safety Precautions
- Historic Structures Precautions
- Submittals
- Quality Assurance
- Delivery, Storage and Handling
- Project/Site Conditions
- Sequencing and Scheduling
- 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
- Drywall and joint compound
- Nails and screws
- Joint tape (cloth mesh preferred)
2.02 EQUIPMENT
- 6 inch taping knife
- 12 inch taping knife
- Float
- Hawk
- Sanding sponge (medium fine grit)
- Stiff putty knife
- Goggles, work gloves, and dust mask
- Hammer and cold chisel
- Needle nose pliers and wire cutter
- Screwgun and drill
- Spray bottle and drop cloths
- Tin snips
- Vacuum
PART 3–EXECUTION
3.01 EXAMINATION
- Determine the extent of damaged plaster. Look for:
- Holes.
- 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.
- Chipping, flaking and delamination of plaster due to water infiltration.
3.02 ERECTION/INSTALLATION/APPLICATION
- Removing Deteriorated Plaster:
- 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).
- 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.
- Cut the plaster back to the nearest studs to make a regular opening, and re-secure the lath with drywall nails.
- Use plaster washers and wood screws to re-secure weakly-keyed areas of sound plaster to the wall or ceiling.
- Knock any plaster stuck between the lath back into the wall cavity.
- Vacuum all dust, loose plaster, and other debris from the hole with a shop-vac, or sweep it out with an old paintbrush.
- Making a drywall patch:
- Shim the drywall as required to bring it up flush with the surface of the adjacent plaster.
- Cut a drywall patch to fit neatly in the opening.
- Nail or screw the drywall in place. Nail heads or screw heads should be set slightly below the surface of the drywall, but without breaking the paper.
- Using the 6 inch taping knife, fill the joint between the drywall and the plaster with a small amount of joint compound.
- Apply a fairly smooth, heavy coat of compound over the joint a little wider than the tape width.
- 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.
- Apply a thin layer of compound over the tape and apply a first coat of compound to nails or screws.
- Knock off any ridges or pimples that develop from shrinkage and cracking in the compound.
- 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.
- 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.
- Touch up low spots with additional compound or high spots by light sanding with a wet sanding sponge.