Building a post-frame cover for a client's 5th wheel — looking for a gut-check on a few things before I finalize plans
I'm a GC in the Bitterroot Valley, building an open-sided post-frame structure to cover a client's fifth wheel (2022 Jayco North Point, ~43' long). Rough specs: 18' wide x 46' long, 15' eave height stepping up to an 18'-9" ridge (5/12 pitch), 14 posts at 8' O.C. down both long sides on concrete footings, a beam running the length, and engineered roof trusses on top. Open on all sides — no walls, just posts and roof, with black hardware throughout for a timber-frame look. Metal roofing, brown Box Rib panels.
I've got a rough materials plan together but want a real engineer's sign-off on the structural pieces (footings, beam depth, truss/purlin spacing) before ordering anything, and I'm also trying to sanity-check some of the numbers other local post-frame guys have given me against what's actually standard practice. Posting my current questions below — appreciate any input from people who've built similar structures, especially in real snow country.
Structural / Engineering
- For an 18' clear-span post-frame truss at that snow load, what depth should I expect on a 7.5"x7.5" glulam beam spanning 8' between posts — does 7.5" depth sound right or undersized?
- Is 8' O.C. truss spacing standard practice for post-frame in heavy snow country, or does that vary more than "everyone locally says never wider than 3'"?
- For an open-sided (no walls) post-frame structure, what's a reasonable ballpark on footing depth/diameter and whether belled footings are actually necessary vs. straight sonotubes, given Ravalli County frost depth (~42")?
- Anyone have real experience with beam splices on glulam — is a black steel plate through-bolted on both faces (sandwiching the joint, landing over a post) the standard way to do this, or is there a better/more common detail?
- For truss-to-beam hurricane ties, is it normal to wait for the truss company's stamped uplift reaction numbers before picking a tie model, or is there a rule-of-thumb tie that's safely oversized for something this scale?
- Do purlin clips (uplift-rated) actually get used at every truss crossing in practice, or is that overkill for a residential-scale post-frame roof?
- Any input on whether additional lateral/diagonal wind bracing is typically needed on a fully open post-frame structure beyond standard knee braces at each post?
Material choice
9. Solid 8x8 timber vs. boxed LVL vs. straight glulam for exposed posts/beams on a timber-frame-look structure — what's actually held up best for people long-term, especially in a high-swing climate (hot summers, real winters)?
10. Anyone had issues with incised PT lumber checking/cracking badly enough to regret using it on an exposed structure, vs. going untreated DF/L in a covered, bracket-mounted application?