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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?

View of the upper floor

Top of Engineering plan

More details of engineering plan

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  • See those purlins on top of the trusses? Those are your sign. If they'll carry snow load they're likely to carry drywall just fine. Like Ed Beal says, though, verify that the trusses are designed for a ceiling load.
    – isherwood
    Nov 23, 2020 at 21:35
  • I know you're asking specifically about a drywall ceiling but if it turns out to be a no go then would you consider a drop-ceiling? youtube.com/watch?v=mebf6FhWKlU
    – MonkeyZeus
    Nov 24, 2020 at 14:27
  • @isherwood , I've updated the question with a copy of the engineering plan on the trusses. I see that they're rated for load, wind, snow, etcetera, but I do not know what those mean. I mentioned in a comment below that I will be reaching out to a structural engineer friend to get some verification.
    – ModulusTwo
    Nov 24, 2020 at 14:58
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    Your trusses are designed for the added load i did not try and read the entire thing on my phone but when I go to 24” on center I use 5/8 Sheetrock it doesn't sag as bad as 1/2”.
    – Ed Beal
    Nov 24, 2020 at 15:08
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    The relevant number is BCDL=8 psf - bottom chord dead load, 8 pounds per square foot. Whatever you hang off there needs to add up to less than that.
    – Ecnerwal
    Nov 24, 2020 at 18:10

3 Answers 3

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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)

enter image description here

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.

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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.

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  • Thank you for the input. I can try to update my question later with a blueprint of the engineer trusses. I know they are rated for a certain load for snow but do not know the capacity. (Mid-west USA) I also know a structural engineer that I will reach out to for more details.
    – ModulusTwo
    Nov 24, 2020 at 14:45
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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.

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    @Ecnerwal this is a diy stack exchange. . . just assume we're as dumb as can get, he was giving constructive criticism, don't take it personally. I don't even know what a 2x4 is, let alone whether they're usually vertical or horizontal
    – pythonian29033
    Nov 24, 2020 at 7:06
  • @Ecnerwal , That is the plan right now. Thanks for the input!
    – ModulusTwo
    Nov 24, 2020 at 14:52
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    @pythonian29033 A 2x4 is a common lumber in the US, approximately 2x4 inches (~5x10cm) in cross section. It's actually a bit less than that for historical/technical reasons, but close enough. They can be oriented any way you need them, though I mostly see them in walls, not ceilings.
    – Darrel Hoffman
    Nov 24, 2020 at 15:41
  • @DarrelHoffman thanks man
    – pythonian29033
    Dec 8, 2020 at 4:06

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