My shop uses 4ft trusses, finished inside, stick built. My builders assured me it was cheaper to do so.
There are literally dozens of ways to build a shop/garage/barn. And I wouldnt say any one way is better than the next. And cost all comes down to the cost of the building materials AT THE TIME of purchase.
There are SO many variables....and they are all interconnected. Change ONE variable....and it changes ALOT.
Stickbuilt requires a foundation or a monolithic pour. That adds cost and so does sheeting before the metal goes on. But you save the expense of treated posts and post holes.
Another variable is 4' vs 8' OC trusses. IF you are building a barn that is 64' long, that will take 17 trusses at 4' OC. Those trusses are likely gonna be ~$150ea for a 32' or so span. Thats almost $5000 in trusses, then you need a double 2x12 header. And 2x12 lumber aint cheap.
Jump that to 8' trusses and set them right on the posts. Only need half as many trusses (9)....and they are more expensive but not double. Like maybe $225ea. So only about $2000 in trusses. You also dont need the 2x12's for headers. But now you add complexity for the purlins standing on edge. Either hangers....or blocking....or long spikes driven by hand which adds significant time and labor (cost to build). Then there are 10' or 12' OC posts and trusses. Cheaper yet for just the trusses, but now 2x6 purlins on edge and definitely need hangers...so there is that added cost.
For walls, you can use 2x4 girts nailed on the outside of the posts and the building goes up quick. But then you have to do the same thing on the inside if you plan on finishing. Another option is 2x6's laid flat between posts (like a stud wall only horizonntal). Takes more time to frame up the initial shell, but that pays dividends in the long run because you are already ready to finish the interior. And actually, a single 2x6 is cheaper than TWO 2x4's (one inside and one outside).
Again, dozens of ways to build. None are really better than the next. Because there is always a tradeoff.
But dozens of buildings I have designed and laid out either for myself or for friends/family....cost was never really a factor. Because on a building with $30k of material (finished and concreted)....the difference between posts vs monolithic vs footer/block wall, and 4', 8', 12' OC trusses is rarely more than a few hundred bucks at the end of the day.
In reality, the decision on "how" to build has came down to Labor, equipment, and time at hand. Trying to get a shell of a building up before winter sets in it might be best to bang the wall girts up on the outside and deal with the inside later vs 2x6's horizontal between posts. Or not having the skill or time to lay block or equipment to dig footer so setting posts might be the best.
When I built my 40x72 shop....I had a backhoe and a post hole digger. The price of the block and concrete for a footer (I know how to lay block and have backhoe to dig footer) was darn near identical to the cost of treated posts and a header all the way around the building. IT took more labor to build my building, but didnt cost any more money to lay a 6-course block foundation and then build the walls in 16' long sections and sit upon the wall.
Like I said, lots of ways to build and I wouldnt call any of them "wrong" ways. BUT, using posts AND a monolithic pour dont make sense to me. only thing I see it saving is the sheeting because you can now put horizontal girts for the metal....and maybe that makes sense with current prices. Gotta adapt to the lumber market I guess
