Portland cement plaster has been used over metal lath on the walls of a refrigerator room that operates at temperatures of 32 to 35 °F. The metal lath is supported on wood studs with polyethylene between the lath and studs. The plaster has cracked and peeled from the walls, and when patches of the same material are applied they soon fail. Patching must be done at temperatures not much above freezing. What will work? We have about 200 lineal feet of cracks to repair.
There are several special cements on the market made of magnesium ammonium phosphate or regulated-set cement which set rapidly at low temperatures. These can be used in a plaster instead of the portland cement used previously. Another possibility is to use hot mixing water (100°F or hotter)—at least experimentally. Cracks should be widened and cleaned out down to bare metal lath. The depth of the patch would be about 1/2 inch.