I am currently building a 30 x 48 with 12 foot tall walls metal sheeted building. There is also a wrap around small porch on the front, two 30 50 windows, and two 30 00 doors and two 9x9 foot garage doors. There is a 30 x12 foot gravel lean too on the back.

The footers for the concrete pad and stem wall are curing now. They were poured on Friday. I plan on the exterior walls being 2x6 framed on 24 inch centers. I am using trusses for the roof. I have an Amish crew that is going to do the framing and metal sheeting. I planned on the trusses being on 2 foot centers. They said that for my area, I could save a bunch on money by doing 4 foot centers on my trusses since they are engineered trusses.

We dont get alot of snow here in Lebanon, MO (SW Missouri) but, I dont want the roof caving in either. What will I loose by going to 4 foot centered trusses? Will I be less resistant to high winds or snow load? Or is 4 foot common now and I am over building???

Your local building code should specify a snow load in pounds per square foot and the trusses spec will determine truss spacing.

This. And piece of mind is very underrated.

You mean to check the local city build code? There is no code, permits or inspections in the county here.

Your trusses will be designed to some parameter, probably somewhere around 30LL-10DL-10DL @ 2’-0” OC. If you space them at 4’-0” on center, you’re cutting your loading in half or 15LL-5DL-5DL.

Based on your situation, put them 2’ o.c.

This, peace of mind is worth a lot

Back in the day, there were no permits or codes for the rural areas outside of city limits here in the central and eastern UP. During the extremely heavy snowfall during the winter of 2018-2019, over 250 shed and garage buildings collapsed. Some had survived 30 to 40 winters before the big one. Our Cleary engineered and built 36 x 48 x 14 wall pole building didn’t even creak or groan with the snow load. Peace of mind is priceless.

Yep the extra cost of a few trusses is nothing in the long run
Another good idea is to upsize all lintels, small cost but less deflection makes a building look much better in the future

Insulate it if you can, it will be amazingly cooler in the summer.

No offense, but that is not a metal building.

most pole barns in this area the trusses are on 5/6 foot centers. I am about 100 miles north of you.I built a pole barn home in 2004 and my trusses are on 5ft centers

Talked to a buddy who used to build them, don't have to worry about snow, but I'm planning on a car lift, and maybe a mill. he told at least a 6-inch fiber reinforced slab. Might go big enough to build a decent side home inside of it, a barndominium. and try to keep it ag so I'm not paying a lot of property tax. get a few goats, the old lady has always wanted a couple of goats.

Make it big----er!

My son has a 40x50' garage/shop on his property. His wife rented a building in Slater Iowa where she cut hair. The derechio in August damaged the building so he had to build her a hair salon inside of his garage. It takes up about 20% of the floor space and blocks one of his over head doors. I'm sure he wishes he could do that garage 50x50 right now.
kwg

Insulate it for sure if you are thinking of building living quarters in it.

And don't cheap out on the wall framing, either. Go 16" centers and forget the 24" BS....

Every pole barn I've ever built or seen had 8' spacing on the rafters with 2x4 purlins between them. Seen every pole barn/shop but that way from Minnesota to new Mexico. How much snow do you get in Missouri?!?!

I'm guessing you are building it similar to a house and sheeting it with OSB on the roof? In that case I have no idea. Given the cost of building materials though I'd be looking to save wherever I could and pencil it out. Maybe check with a local building engineer?

Most pole barn and metal building roofs are on a low pitch- go to a 6/12 pitch with metal roofing and leaves/snow will slide right off- mine is on 4' centers. 42x42 stick built with no trusses.

I think you would be amiss to not go with 10' garage doors if you can fit em in... As far as the framing, I like the pole barn layout , but your plans are totally fine. 2' OC on the walls is plenty and I would run a double top plate, but beauty is in the eye of the beerholder! Make sure you hurricane clip all the trusses to the top plate, as some areas do not. One cannot over sway brace the inside of the trusses either, just sayin!