I am building a garage extension, 10′ x 14′. The original is sheathed with 3/4″ cedar (I think) shiplap siding and nothing else (no ply, etc.). It is probably 60-70 years old.
I am putting on pine 3/4″ shiplap siding, because it was the only thing I could find that matches the existing profile (#106 or 107, coved at the top, sometimes called “specialty”). But the pine seems pretty floppy.
I wasn’t planning on sheathing with ply or OSB, but now I am wondering if that is a bad choice. The pine probably has enough tensile strength, but its lack of stiffness worries me.
Should I sheath first even though the original is just sided?
One other question: I am planning on using 8 penny galvanized box nails to hold the siding (instead of finish nails that were used on the original). Any thoughts on that?
Thanks, and happy holidays to all.