Wood framing question (ceiling joists and roof rafters) 1

[conradlovejoy]

Has anyone ever come up with a simple solution (simple in terms of construct-ability in the field) for a situation in which the ceiling joists and roof rafters need to be connected (preferably over, or at least near to the wall supporting them) but are to be at a different spacing?

 

[jayrod12]

Why would you design them at different spacings? Change the spacing on one of them (I'm assuming it's the rafters at the larger spacing) to match the other and then size the members accordingly. Cost difference can't be that bad.

If you had to, you would need to provide adequate connection between the rafters and the top plate to support both vertical and lateral loads. Then design your top plate to be able to tranfer these loads between the supporting members, studs for vertical load and ceiling joists for lateral, provide a connection between the ceiling joists and top plate for the lateral load. Pay attention to the splices on the top plate.

As far as simple, you could do it with simpson strong-tie connectors, that's fairly simple.

 

[msquared48]

Well, if you are talking the need for using the ceiling joists as collar ties to take the kick from the rafters, with the rafters at 24 and the ceiling joists at 16, every other rafter should be able to be connected. Provide enough capacity in that connection to make up for the rafter that is not connected.

Same idea goes for other rafter/joist spacings.

Mike McCann
MMC Engineering

 

[conradlovejoy]

Thanks for the thoughts. As for the reason they are at different spacing is beyond my control. This is a repair and only rafters on one side of the building are being repaired/replaced, as well as a few ceiling joists. The rafters on the other side of the building that aren't being replaced are at a non-uniform spacing for some reason or another, but are closest to about 24" O.C. So that creates a different situation at my south wall than at my north wall. I agree that only a few of the new joists won't line up close enough to a rafter to be able to toe-nail them together, and that a strong tie connected to the top plate should be more than adequate, if anything is needed at all. Thanks.

 

[XR250]

Fasten a 2x10 plate flat to the top of the ceiling joists (perpendicular to the joists). Then add a Simpson LTS12 from the plate to each rafter.