reinforcing plaster ceiling from above
Greetings, My kitchen ceiling has 3/8" rock lath + 1/4" plaster. In replacing an old circline fixture with a fan I noticed about four hairline cracks around the 4 X 4 box hole radiating out about 10" to 12". I am concerned about the dynamic load the rigidly mounted fan my transmit to the ceiling and don't want these cracks to grow. If I screwed a sheet of 3/4" OSB or plywood into the 2 X 6 joists from the attic would this distribute the load better and stiffen the ceiling up?
Thanks for your input.