Side by Side - Multi-family Wood Construction at Tenant Seperation

[Insp-struc]

For multi-family (2 or 3 stories) wood construction with the units (homes) side by side in a building configuration, how to get the lateral load (From wind) to transfer throughout each unit on exterior walls.

For most cases between units, there is 2" GYP shaft liner with 1" air space on each side before the wood tenant separation walls (continuous from foundation to roof sheathing). This leaves the floor diaphragm of the "End" unit to distribute the lateral loads to the exterior walls. This is fine, but when the exterior wall does not have a continuous plates, due to the shaft liner and air gaps, how is that load to be transferred throughout the rest of the units?


*Consider continuous wall sheathing between units

Most of the time these town-home units do not have much wall to work (smaller widths and windows) with and for higher wind zones it becomes difficult for the end unit to be design to resist all wind forces.

 

[RobertHale]

When I was doing these, we considered each unit as needing to stand on its own. The logic being that the units on either side could be destroyed or demolished and the unit in question could be expected to take wind and seismic load. You really need to look at how the units are being sold. The last one I did before leaving that company turned contentious since the openings reduced any exterior shearwalls to the minimum required by the aspect ratio rules and the architect refused to let them stack. I ended up having to use a tie-down system, utilize non-stacking interior shear walls, and transferring large overturning couples (that had to include the overstrength factor) out into the floor system; frankly, it was a nightmare.

Robert Hale, PE