1. Save it. Original plaster is a key historic element of any old house. Removing it, especially to replace it with inferior drywall, significantly changes the historic appearance and value of your home.
2. Don’t use buttons. Plaster that has detached from its substrate (lath) needs to be held back in place to be saved, but plaster buttons can further crush plaster, and they create a surface bump that must be skimmed over to blend in. Glue-injection reattachment is a more secure option.
3. Fill in the cracks. Taping over cracks rarely works and is usually unsightly. Dig out cracks in a V-notch fashion and infill with plaster or setting compound for a longer-lasting, more invisible repair.
4. Match up repairs. A like-and-kind mix is preferable, but mixing modern gypsum plasters with traditional materials like lime putty and hair offers a faster solution that will still blend in well. Coarse plaster (like Structolite) best mimics the oldest plasters, while finish plasters create smooth surfaces befitting later eras.
5. Practice first. Try your plaster mix and trowel technique out in an inconspicuous area or on a board before tackling a high-visibility repair.
