Recently I had posted an article on closing tops of corner trims (https://www.hansenpolebuildings.com/2018/10/closing-top-of-corner-trims/).
Reader MATT in CINCINNATI has opted to go with a light gauge steel framed building, rather than a post frame building, however he had questioned my original article:
“Thanks for all of your informative posts, they have been quite useful in my journey toward my dream barn/house. I am finalizing design of a beautiful K Building. Hard to argue with a full perimeter footer and steel truss frames. My barn will have a porch similar to the attached picture. I am hoping you might revisit your post on “Closing Top of Corner Trims”. I agree in regards to the picture in your original post that spray foam would work when tucked up under the soffit with minimal weather exposure. However, in the attached image, with the top edge of the lower corner trim exposed directly to the weather, it seems much more important to get it sealed. Perhaps slitting into the endwall siding and extending the J trim from the porch past the corner trim would provide a better solution? Either way it seems copious amounts of caulk are in order.”
In an ideal world you could use a combination of #2 (the Emseal expanding closure) and #3 folding down the top of the corner trim. The Emseal by itself will provide a watertight seal. I always try to avoid cutting into the siding as much as possible.
I do have a concern about your K Building’s 2×6 #1 Southern Yellow Pine (SYP) roof purlins, spanning 15 feet.
20 psf * 24″ on center * 15′ span ^2 / 8 * 7.5625 (section modulus of a 2×6) * 1.15 (Cr for repetitive members) * 1.15 (Duration of Load) * 1350 (Fb for 2×6 #1 SYP) = 1
20 psf is the minimum design live/snow roof load by Code, however there is no allowance for dead loads (weight of roofing, weight of the purlin itself, etc.). I would recommend using 2×8 purlins.