How to Repair Plaster on Lath

For long-lasting results, reattach loose lath and plaster surrounding the patch

We’ve all seen it, and we’ve all done it. To mount an HVAC duct, we’ve cut through a plaster wall with a recip saw, sending plaster flying and leaving the lath flapping. No problem, the drywallers will handle it, right? Wrong. The most durable plaster repairs are made with plaster, not joint compound. Plus, without the proper prep work on loosened plaster, any patch is doomed to failure.

To show you how the pros do it, we’ve adapted a video called “How to Repair Lath and Broken Plaster,” by Rory Brennan, who has been repairing plaster for 30 years. Brennan owns Preservation Plastering in Brattleboro, Vt., and maintains a YouTube channel with many plaster repair how-to videos.

Follow the photos and captions for a step-by-step look at Brennan’s process, which includes products for a patching system he developed called Big Wally’s Plaster Magic.