I'm finishing my basement and planning out my framing for a 20 ft wall. At the ceiling and running alongside the length of the wall is my duct work. The duct is 3 ft wide for about 8 ft long then it tapers down to 2 ft wide. For the 3 ft wide section - it is butted up against the existing wall and ceiling joists. I therefore have no means to attach my top plate to the ceiling joists. The 2 ft wide duct is out from the wall - so I do have acess to the ceiling joists.
How do I handle my top plate where I have no access to the ceiling joist - just butt up to and glue to the duct work? (BYW - duct is insulated) Then step up for the remainder of the top plate and nail into the joist. Will wall be sturdy enough in this manner? Any advice appreciated - thanks...Hope I explained this well enough?

 

This may help give you some ideas:

http://members.shaw.ca/darrenfloen/wall.html