By using 4 inches gap first drill ¼ inches holes into plaster ceiling with the help of drilling machine. Pay your full attention and make sure not to drill so deep that you damage the lath. Clear the dust from drilling with the help of vacuum cleaner.
Take a water spray bottle and spew some water on the holes in order to make the plaster soft. Now spurt some latex glue by using caulking gun onto the holes. Clean out extra glue by using dampened sponge.
Between the plaster ceilings secure plywood board where you just made repairs and floor, now push the ceiling slowly upwards to the lath in order to fix in the added glue. Cover the plywood board tops with plastic sheets in order to guard plaster from board’s sharp corners. Now leave it for at least 24 hours so repair could sit and alleviate.
Now it’s time to remove plywood boards. Remove them off and by using putty knife, apply the joint compound to fill the holes with plaster ceiling.
Now let it dry! You are done with repairing plaster on ceilings.