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???

You don't need 2 foot centers , 4 foot centers are plenty strong ..

Go to Menards web page and go to the design a pole barn section. You load your zip and what size a building you are making and it will show you options on trusses from 4' to 9' spacing. I did 4' on a 24 x 32. I will bet we get more snow and wind than you do. We just had 90+ MPH wind a couple days ago. It will be fine with 4' spacing.

4' is fine...the lateral and corner bracing on the ends is what really does the legwork on stability....it's when the endwall blows out that the roof caves in

Im guessing the trusses built for 4' oc are built stronger then those built for 2'oc? And cost more also.

The best advice I can give you is go bigger on your doors.9x9 is way to small.The very smallest door opening I would use is 10 foot and 12 would be better.

True on the Doors^^^

With a metal roof there’s not much of an advantage of having it on 2 foot centers, the rafters will be built heavier.

here in northern michigan where we get lots of snow the county has load limits we have to meet. in the southern counties here i believe its 70 pounds per sq andits 90 pounds here . my trusses are 6 foot,like was said its how they are built 2x6,2x8,2x10,2x12 makes the differance and the pitch a 6/12 pitch cleans itself better than a 5/12 pitch.

good luck

If they are built right 4’ shouldn’t be a problem. In the beginning stages of my second metal post frame build in Nebraska. Both have 9’ truss spacing.

I also agree on the doors. Go bigger if you can. With 12’ side walls I would be looking to go either 10x10 or 12x10. I went 14x14 on my last building thinking it would be enough. Wish I would have went either 16x14 or even 18x14.

Yes on the bigger doors -- 10-12 ft wide -- much better ..

As has been said, get a bigger door.9 wide is to small to drive a pickup with mirrors in, it is like threading a needle.
not one time over the years of framing wood and metal buildings did anyone ever say.....them doors are to big.
If you have a walk door into the shop, think about a bigger door for it also.

its all about weather your going to finish the ceiling , and I would go with bigger doors

Im 4' centers but pole construction. My end wall poles go to the top of the truss. The end truss on both ends is on the ouside of the pole. So the ones in the center go to the peak. The end trusses being held like that is what keeps it falling over like dominoes and provides wind strength. Then there are really long boards angles from near the end walls peak down and to the outside wall through the trusses to an outside wall providing outtrigging support... fastened at each truss. Using the metal hurricane brackets on the trusses at the wall add significant support too.

I suggest making your bottom stringer in the truss a 6 or 8 inch board and using a truss that is open in the middle so you can floor and use the attic for storage. They make "bonus room" trusses but those are costly but roomy... I just used a truss design that was open in the middle and built shelves off to the sides in the truss area. All of which also add strength.

If you can afford it, I'd spray foam insulate it also. Unbelieveable the diference in heating it in the winter time

I’ve checked into it. They definitely don’t give that stuff away.

Why not just install one 16' garage door?

I would also check with your insurance company in regards to your spacing on your trusses. There may be a big enough increase in premiums to justify the additional trusses. And as far as using the additional room for storage, I wouldn't unless the trusses are designed to do so. Seen where owners have do so and overloaded it to where trusses have broken, especially when going with 4' OC.

"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???"

You can do what you want to do.
A couple of things to consider. Will trusses at 4' o.c. meet the local building code? Very questionable.
In stead of listening to folks that do not have a penny invested in your project, and darn sure won't be held liable if you are acting as the general contractor, why not ask the truss company you are buying from. Yes they are '"engineered". That can mean a lot of different things.
Ask the Amish builders to show you in the IRC or IBC where it says you will be fine.

I have no idea about snow load in your country but could easily look it up. What other weather events are common where you live?

There is not a chance in the world I would ever put up a 30' x 48' building with trusses at 4 feet on center. I am probably not as experienced as some posting, but I feel it is a mistake. Yes, those extra truss will be an added expense. There are some places in life or in a project to save money. In my opinion, this is not one of them.

Before you consider using the trusses to store stuff on you best check with the truss manufacturer. Typically trusses are not designed to carry any significant load on the bottom cord. Yes there are trusses designed such as an attic truss that allows the use of the second floor, but most are not designed to carry weight.

Again, ask your local code enforcement official.

Good luck

My 2 cents. I just had a building bid to me by a steel building outfit that is supplying two very large storage buildings to me. The building I speak of is a bit bigger than yours and is for my northern Mn property. 4’ centers on trusses met code easily. I think we get a snow load rating beefier than most the country except maybe Maine and up in the Rockies/upper Mich.
A lot depends on the perlin sizing and spacing.
My two storage buildings trusses are 10’ on center with 2x6 perlins fit and bracketed in between those are 48’ long trusses. Shows what they can size up to and engineer with our snow loads.

Osky

Just remembered, I bought two metal buildings standing a few years back that I am to have moved ( gotta get after that ) one that I really like is very near the OP size. I am sure those trusses are 6’ on center. It’s all in the truss design.