does anyone know if it's possible to suspend a drop ceiling from "solid bridging" (2x6), between joist above(as opposed to right to the joist), if you need to run the main tees parallel to joist instead of perpendicular...also why can't you simply run the main tees parallel with the joist,right underneath each corresponding joist if they run on 16 anyway...thanks for any input

Can you be a little clearer on what you want to do. I keep getting lost.

Remember that drop ceiling is either 2 X 4 foot or 2 X 2 foot panels so your tees need to be on that 2 foot centers.

Are you tring to hang below the joists?

Common (American) frame construction is based on the 4'x 8' sheet of ply wood. Thus framing either is 24" on center or 16" on center.

16 inches on center means that sooner or later your frame will reach 4' then 8'.

A grid of 16 inches to equal 4' x 8' would be 3 across and 5 up and down. I'll try to illustrate it:

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In 2x2 (feet) wire hung drop ceilings wires are ran every 4 feet down to support the ceiling frame by passing every other panel. For 2 by 4 drop ceilings each panel is hung at the corner of each panel, on the frame. The 2 foot width runs the length of the joist.

24 inch on center is common in many ceiling only joist systems. 16 inches is used for floor supporting ceiling joist (like in a two story house).

In older houses where joists were hung at irregular intervals (not 16 or 24 inches on center) the installation of a drop ceiling requires a secondary 'frame' installation - usually 2x4s screwed up under the joists crossing the joists. This is most commonly done laying the 2x4 flat, thus the thickness of the 2x4 (1.5") is up and down or dropping the ceiling height 1.5"

It is also done with 2x2 and I have seen it done with 1x3, 1x4 material. It is against code in earth quake regions to use 1x material. Other areas may allow it.

Around here code DOES NOT allow a drop ceiling be hung on/off lath and plaster material, back east Code DID (I do not know currently) allow it on some (not all) of the ceiling. I think something like half of the hangers had to be in a joist. Drywall seems to always have been not allowed - since drywall is not that structurally sound.

I hope my answer helped.