POLE BARN QUESTIONS

[HAPPYNC]

I'm looking to build a open sided 40x60 pole barn. There will be a metal truss lean-to on one side and eventually two or three shipping containers on the other side of the barn with a lean-to shed over them also.

I'm using metal trusses pre-engineered for 140 mph winds. I'm in central NC and the highest winds I've ever seen was during Hugo in 1989 with sustained winds of 55 mph and gusts of 85 mph.

My plan is to use 20' 8x8 PT post, 10ft on center. I don't think I need it but I would probably do 2x10 banding around the top of the post with angle bracing on each post. The metal trusses have their own horizontal truss ties.

I would like a minimum of 13 ft sidewall height, preferably 15 ft.

My questions are, is the 8x8 enough for either 13 or 15 ft height and how deep and wide should the hole be? The frost line is only 12 inches. I figured on using concrete and cross drilling 2 or 3 holes in the post with rebar alternating north/south and east/west.

 

[EddieWalker]

Are these treated 8x8's? I've never seen them before, only 6x6 treated posts, which would be more then strong enough for your application, or just about any other application. The only 8x8 posts that I've ever seen or installed where cedar, and they cost 5 times as much as treated 6x6's

 

[RNeumann]

This guy has good info.

RR Buildings
- YouTube

Designing and engineering your structure when you need a roof rated at 140mph is a bit short sided. I’d spend a few bucks having an engineer answer those questions and back it up with their stamp .

 

[3Ts]

With just the roof and no sidewalls, it will wiggle, but should be ok. There are slenderness ratios (cross section vs. height) that you'll need to watch for and can find them on the web. It will wiggle no matter the size of columns until they are cross braced which essentially means a wall. I question the 10' spacing because there will be times you'll want to be wider to get stuff in and out.

 

[M5farms]

Yes 8x8 will be sufficient . I have them on my 50x60 , when I built my 32x60 in November I used 6x6 but came off each side with 15' leans and used 6x6 on them . I put my holes at 48" used a 12" auger for 3' dug the rest of the way down by hand with hole diggers

 

[HAPPYNC]

With just the roof and no sidewalls, it will wiggle, but should be ok. There are slenderness ratios (cross section vs. height) that you'll need to watch for and can find them on the web. It will wiggle no matter the size of columns until they are cross braced which essentially means a wall. I question the 10' spacing because there will be times you'll want to be wider to get stuff in and out.

Well, to be perfectly honest, I have everything bought but the post and concrete. I bought 2x6x12 for the purlins. The business I bought the metal trusses from is just a reseller/retailer. Afterwards, I found out the trusses are from a company in Alabama just above Pensacola, FL which explains the higher wind rating.

When I checked out their website and then called and spoke to someone, I read and was told 10 ft max. It WAS originally gonna be a 40x72. I'd rather be safe than sorry and maybe just add another truss later on if I still need it. The bad thing is I'll have to chop 2 ft off every purlin. Argh!

 

[HAPPYNC]

Are these treated 8x8's? I've never seen them before, only 6x6 treated posts, which would be more then strong enough for your application, or just about any other application. The only 8x8 posts that I've ever seen or installed where cedar, and they cost 5 times as much as treated 6x6's

Lowe's in this area source their lumber from a local supplier. You can go to the Pro Desk and special order bigger and longer than what the stores stock. They are pricey but I can get a discount on them that helps a little. They are pressure treated pine.

 

[HAPPYNC]

This guy has good info.

RR Buildings
- YouTube

Designing and engineering your structure when you need a roof rated at 140mph is a bit short sided. I’d spend a few bucks having an engineer answer those questions and back it up with their stamp .

I've seen his vids. He does quality work. I don't need a 140 wind rating. That's just what they came as. The company I bought the trusses from buys them from a coastal AL truss fabricator which explains the high wind rating.

What's funny is I called the permit office....always a cringe worthy action. They want engineered footers and post design even though the trusses came with engineered drawings. The permit was around $330. A local engineer wanted $3000 to draw it up. Said it was 40-50 hours work at $75/hour. That's a great price..........if you're an engineer. Not so much for me.

The flip side of that is the permit office said if I was a farm, I needed nothing more than a Farm# from the local FSA (Farm Service Agency) and my cost would be no more than a zoning permit just to make sure I was zoned Ag. Cost....$10.50. Luckily, I have a farm number being some of my land is leased.

Guess which route I'm leaning towards?

 

[KennyG]

You are more than good with your approach. Around here, I don't think I've ever seen 8x8s used. My pole barn 40 feet wide and uses 4x6 posts on 8 foot centers. If you only have 13 foot sidewalls, I think 16 foot long poles would be fine with your limited frost depth. I have 12 foot sidewalls with 16 foot poles but our frost depth is over 3 feet.

 

[HAPPYNC]

Yes 8x8 will be sufficient . I have them on my 50x60 , when I built my 32x60 in November I used 6x6 but came off each side with 15' leans and used 6x6 on them . I put my holes at 48" used a 12" auger for 3' dug the rest of the way down by hand with hole diggers

That's good to hear. I have a 12 inch auger bit but thought about renting an 18 or 24 inch and digging 48 inches deep. I was looking to do the same on the lean-to with the 6x6 posts. It's a 24 ft lien-to.

Is yours in Florida? If so what type of soil do you have? Mine is red clay but I have a good bit of "potato rocks".