Our ceiling has 24" OC joists, and we are adding a mini split ceiling cassette that needs 16" OC joists.

Can I add a "partial" ceiling joist to support the mini split? That is could I add two cross braces/members and then a joist that only spans 5 feet to support the mini split? I've illustrated this in the image below.

Or, if adding a joist would it have to run the full span (20')? Or is there a better way to support the mini split?

Ceiling schematic

  • Is the 16" O.C for attachment screws? If so one 2x6(on its side) across the two foot space might be enough.
    – crip659
    Jan 5 at 17:32
  • Yes it's to attach the cassette to with 3 screws into each joist. Wouldn't there be some issue in the rotational force of the 2x6 on it's side?
    – r_alanb
    Jan 5 at 17:45
  • The cassettes weigh about 90 lbs
    – r_alanb
    Jan 5 at 17:55
  • What is a mini split ceiling cassette ?
    – D Duck
    Jan 6 at 9:54
  • 1
    @DDuck "what is a web search using the terms you put in italics?"
    – Ecnerwal
    Jan 6 at 14:20

1 Answer 1


You don't even need full 2x6 here. 2x4 properly aligned should provide adequate support. I would use the proper hangers for the joints.

2x4 joist hanger

Image source, no endorsement implied

Don't think of it as adding a joist, because it's not. You're adding framing to support the cassette, nothing more.

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