How to frame for a drywall ceiling with 8 feet between trusses?

Question

I have a post frame building that was recently constructed where the post and joists have 8 foot on center spacing. The building is 38' x 54' and we had a 2nd floor built on the North end of it which measures 38' x 30.  This 2nd floor is to be a framed in and finished "living space". I didn't consider how I was supposed to do a drywall ceiling on the 2nd floor when the trusses are so far apart.
I was considering using 1x3" 16' furring strips to span over 2 trusses at 16" on center. I'm afraid that an 8' span will still sag with drywall on it.
My other idea was to put 2x4 8', 16" on center, in between the joists with hangers like these
Would either of these ideas work with what I have? Are there better options?

UuDdLrLrSs · Accepted Answer

Assuming you go with the idea of hanging 2x4 ceiling joists, you might consider using a top-mount hanger.
This would take advantage of the fact that the truss members are also a standard 2x size to save time; top-mount hangers would "automatically" be square and located in the correct vertical position.
Example: Simpson HU26TF for 2x6s.
(You could use a 2x6 hanger for 2x4 joists)

Having recently installed scores of the regular kind I think you would appreciate the time savings.

That said, I'm not sure if your truss loading specifications are for bottom-mounted loads? E.g., something like snow load obviously assumes the truss is loaded from the top. So I would double check that detail.
EDIT: Ecnerwal commented that the BCDL=8 PSF is the load rating applicable here.
A sheet of drywall which is 32 sqft weighs around 50 lbs plus you'd need 3 2x4s per sheet, each at ~10 lbs. So the total = 80 lbs / 32 sqft = 2.5 PSF.
So assuming that 8 PSF is accurate you should be well clear.

Final thought - the trusses should be spaced evenly, but might bow a bit in the middle. Before you cut all your joist material I would measure each bay at both ends and look for any irregularities. I never assume anything wood is actually rectangular or consistent.

Ecnerwal · Answer

You'll need the 2x4s (oriented vertically, of course, as implied by the joist hangers you linked to) to span that distance and carry drywall.

Ed Beal · Answer

I would verify your trusses have the capacity to add the additional weight of the strong ties and 2x4s on 16”. That is how I have done it on several buildings but I had the weight added in because I wanted clear span below. Your trusses look a bit lighter than mine were, but I can’t see much of them. But our span was similar.

Answered by Ed Beal on January 1, 2021

How to frame for a drywall ceiling with 8 feet between trusses?

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