Stucco Classico: Gypsum Lath Plaster Repair

Repair Example

This is a repair done on a typical 1950s home.  The plaster was 3/8" gypsum or rock lath, a brown coat of lightweight aggregated plaster, and a hard finish coat.  One day the homeowner found that some of the finish coat had fallen off.  After some investigation, the problem appeared to be caused by a leak from an air conditioner.  Although the leak had happened some time ago, water pooled and then slowly leaked into the ceiling.  The brown coat had a bulge in it, so it was not possible to merely re-apply the skim coat.  After removing the lath and basecoat, joist settlement was observed.  This was corrected by cutting away the small protruding ends of the joists.  New lath, basecoat, and finish coat were applied.  Below are some images (click to enlarge).

This is the ceiling after the loose skim coat was removed:

The basecoat had a substantial bulge in it and had to be removed:

This is the lath ready for browncoat:

The finish coat after completion:

Stucco Classico: Plaster Repair for Pennsylvania