ECN Forum Forums Code Related Discussion Building Codes for Electricians lay-in fixtures, independent support wires....

your answers are located in 300.11, 410.16(C)
If you have 2005 NEC handbook read 300.11 explanation goes over it .
Most ceilings have to be Listed & Labled to carry the additional weight.
Theres also an issue here with Boxes & wiring attacted to ceilings .