Multi-Family Diaphragms

[dodson]

I have been getting request from both acoustic engineers, architects and developers to allow a break in the diaphragm between party walls on multi-family wood framed buildings. These are typically around 20k sq ft and simple wood framed buildings with interior and exterior shear walls and bearing walls. I don't see how the diaphragm can still work if you are cutting it up into small segments the size of a unit? Has anyone dealt with this or come up with good solution that could still provide diaphragm continuity while providing acoustic separation? or has anyone provided this detail and had issues with it?

 

[jayrod12]

If they ask for this, then I tell them that I need to use all four adjacent walls for shearwalls. They tend to make some concessions after we talk about the detailing and requirement for such a thing.

 

[KootK]

This is pretty common in my area and the typical answer seems to be to stitch the party walls together intermittently with light gauge plate connectors to restore shear capacity. Even at that I don't love it though. Once you squander potential in plane flexural capacity from the sheathing, you've really got to nail your chord design and detailing. and that's rare in your typical, joggy looking residential complex. I suspect that many of these things real world work by way of each unit behaving like its own three sided building.