Height of (SmartSide) wall sheathing with 12″ rimboard?
My basic question is whether to use 8′ sheathing/siding panels that barely cover the height of my exterior walls or much more expensive 9′ panels that extend down over most of my rimboard.
My single-story 20×48 house is in central Arizona where we have a Wind Design Speed:of 90 mph – Exposure C and a Seismic Design Category: C, The 8′ walls are framed 16″ oc with 2x4s making up the outer half of a double wall. The walls rest on an OSB subfloor that rests on a 12″ rimboard and i-joists supported by a 2×6 sill plate atop a 30″ masonry stem wall.
I will use SmartSide panels as sheathing and siding. The total height of my wall from bottom plate to top of double top plate is 97-1/8″, 1-14″ more than the 8′ panels that are actually 95-7/8″ high. If I use 4×8 panels, they could extend from 1/2″ above the bottom of the bottom plate to 3/4″ below the top of the upper top plate. If I use 4×9 panels, they could extend from 1-1/4″ above the bottom of the rimboard to 3/4″ below the top of the upper top plate (or 3/4″ higher at both ends).
I understand that the taller sheathing/siding would tie my walls to my rimboard better, but it would cost $700 more, which is significant on my budget, and it would still leave 1’1/4″ of rimboard and the 1-1/2″ of sill plate exposed.
How much benefit would the taller sheathing confer in my wind and seismic conditions? If much, is there a less expensive way to accomplish the same thing with hardware?
How do people typically cover the exposed rimboard and sill plate, whether a few inches or the whole?