2510.5.2.1 Use of gypsum board as a backing board.
BC § 2510.5.2.1
Gypsum lath or gypsum wallboard shall not be used as a backing for cement plaster. Exception: Gypsum lath or gypsum wallboard is permitted, with a weather-resistive barrier, as a backing for self-furred metal lath or self-furred wire fabric lath and cement plaster where either of the following conditions occur: 1. On horizontal supports of ceilings or roof soffits.
2.On interior walls.













