shown in Figure 4 is built directly on top of a poorly formed
concrete stem wall that went up and down like a wave.
To correct a wavy
foundation wall, the framers drove wedges between the top
plates, effectively breaking the connection (photo). The best
solution would have been to wedge between the bottom plate and
sill, then tie the connection together with metal straps or
plates, or with well-nailed, continuous sheathing (top
illustration). The in-place wall can also be corrected with
metal twist ties that connect the trusses directly to the
studs, and with metal straps that tie both top plates to the
studs (bottom illustration).
When it came time to frame the roof, the framers noticed
that the trusses were out of plane. To bring everything back to
level, they drove wedges between the two top plates.
Unfortunately, the shims lifted the upper plate so much in
many places that the nails pulled nearly all the way out of the
lower plate, effectively breaking the connection. This put the
entire truss roof at risk from wind uplift at the overhang.
What the framers should have done was shim the wall directly
under each stud between the bottom plate of the wall and the
sill. The shims can be steel, or wedges made out of the same
material as the plates; a softer wood, like cedar, would crush
under the load. The two plates would then have to be connected
with metal straps or plates. Alternatively, the exterior
sheathing will serve to connect the shimmed plates so long as
it is installed continuously from the sill to the top plate of
the stud wall. Use nails 6 inches on-center along the
entire shimmed portion of both plates and at all edges.
While this is the simplest and cheapest fix, the wall shown
in the photograph can be fixed using metal twist-tie
connectors, such as Simpson's LTS/MTS series or USP's LSTA/MSTA
series, to fasten the trusses directly to the studs. Since the
framing intervals for the trusses and studs differ, this would
provide a solid connection every 4 feet. Where trusses fall
over stud bays, a metal strap could be run up each stud and
across the top of the plates, then fastened securely to both
sides of the stud. This would effectively reconnect both plates
to the studs.