Plaster ceiling deflection limit, when does it fail?

[wesman63]

I am renovating an old house from the 1930's. We gutted the old house and have reframed much ot it. We kept the old floor system of rough-sawn 2x6 16"o.c. w/ 1x4 t and g Fir flooring, no subfloor. I sistered a number of the floor joists and added a couple of additional beams. The ceiling is strapped w/ 1x3 furring 16" o.c. The substrait for the ceiling is 1/2" sheets of blue board (plaster board. Largest span is less then 12'. The . QUESTION - Will a plaster skipped trowel ceiling texture crack under these conditions? Based on an approximate wgt per sq. ft. being 6-8 lbs / sq. ft. Would applying an adhesive to the back of the wall board (on framing), then fastening it the the framing be a major bonus, or will the plaster crack regardless?

 

[htfptm]

I think the anwer will be a resounding "I don't know".

However, you might consider ceiling panels instead. They actually would probably fit the craftsman flavor of the house better and you eliminate the potential cracking issue.

 

[steellion]

IBC limits deflection of roof members supporting a plaster ceiling to L/360 live load and L/240 live + dead.