I wouldn't advise spraying. You won't get as thick of coat as
needed. The advice on that painters' link is good and mirrors my
practice: Caulk any nail/screw spots. Check closely for any gaps in
the laminations within the grooves... caulk/fill those gaps/openings.
Roll, with a 3/4" nap roller (to get deep into any pits & crevices), 2
coats of oil primer, followed by 2 coats of a good exterior house
My garage has T1-11 siding, constructed in 1989. Only a few spots
have become compromised in the past, and most likely because of
hurricane storm related damage (blown limbs against the siding),
otherwise it is in good shape after all these years. It has held up
so well, I installed T1-11 on my shop, primed and painted the same as
the garage - Page down to the bottom for 1 pic on page 1, 2 pics on
page 2, several pics on page 4... shop remodel:
Re - Both garage and shop: I caulked the panel's married seams, when
installing. I installed a drip edge between the upper and lower
sections.... seen fairly well in the pics, page 2, and not well seen
on page 4, but there. I screwed all panels in place and caulked all
screw sites. Don't suppose you have to reinstall any panels, just
though I'd mention my application methods.
I'm not finished with my shop remodel. If you need some supervised
practice with your T1-11 priming & painting techniques, you can come
over and get some free experience, here.