I need advice on pole barn

[mrfrosty]

I am looking to build a 42x30 pole barn, I am not using pre made trusses I will use 2x6's for the roof. Question is how far apart should I spread my post. Most people around here do 10' and 8' we dont get much snow at all(oklahoma). I will be using 4x6's unless I can get some used electric poles from the local coop. Do you think spacing my post at 10' apart would be ok? I will be using 2x8 for the middle post top ridge bracing and I will be bringing my 2x6's off that to the outer walls, not sure what thats called.

[EddieWalker]

Spacing of the poles is a two fold question. One is related to the load on your roof. If you don't have snow, then that makes it easier. If others are building at 10ft centers, then you should be fine doing the same. If it was me, I'd go for 8ft centers as it makes it easier and less wasteful for your purlins on the sides of your poles. You can also use 2x6's for your purlins on 8ft centers. I don't think I'd use 2x6's on 10ft centers. That might be pushing it. With 8ft centers, you can buy 16 foot purlins and overlap your seams.

I'd also consider using 6x6 posts. In some areas, you get a higher rating on your chemicals with the larger posts.

The next thing to consider is your headers at the tops of the posts. With a 30 foot span, you will have a fairly heavy roof. I wouldn't cut any corners here and only consider a pair of 2x12's bolted to the tops of your posts. If you go 8ft centers, you can use 16 ft long 2x12's and overlap your seams on alternating posts. This will give you more strength.

I've built 24 foot trusses, but never tried anything bigger. How are you going to build your trusses? How are you going to install them? What is the height of your walls?

What type of roof are you putting on? If metal, what will be your spacing of your trusses? The spacing of the trusses dictates the size of your purlins on the roof. I like 4ft centers as it allows me to use 2x4's on the flat.

Good luck,
Eddie

[SteelDust]

Originally Posted by mrfrosty

I am looking to build a 42x30 pole barn, I am not using pre made trusses I will use 2x6's for the roof. Question is how far apart should I spread my post. Most people around here do 10' and 8' we dont get much snow at all(oklahoma). I will be using 4x6's unless I can get some used electric poles from the local coop. Do you think spacing my post at 10' apart would be ok? I will be using 2x8 for the middle post top ridge bracing and I will be bringing my 2x6's off that to the outer walls, not sure what thats called.

I think you're really pushing it with the 2x6 for rafters.

Using the AWC rafter span tables, even the table with the highest allowed deflection and 30 lb total load (live and dead), You'll need at least a Doug Fir (No.2 or btr) or similar 2x8 on 12" centers to span 15 feet.

[mrfrosty]

I figured the 2x6's would be good enough, but you are probably right, I just dont want to have to try and put up trusses.

[EddieWalker]

I'm confused. Are you thinking about building a rafter type roof structure with a 30 foot span?

With that much of a span, the only way that I know of to do this is with a truss.

If you put a load bearing wall in the middle fo the building, at 15 feet, you can do a rafter type roof. You will have to span 15feet with your rafters, and build up from there. For 15 feet, I'd use 2x10's on 4 foot centers so that you can use 2x4's on the flat for your purlins.

Eddie

[mrfrosty]

I was looking at putting up post in the middle as well as the outside walls. So the span would only be 15' rafters.I have built smaller buildings the same way, using 2x6's they are very very stout. But, like I said I have never built anything bigger than a 14' x 16' So there is a big difference. I think I will take everyones advice on this.

[FL4400]

I think one of your problems with using just a single 2 x 6 will be the rafter sagging at that length, if you chose to use a 2 x 6 I would double them up and make a 4 x 6 out of it.

[mrfrosty]

I did build a 16'x16' roof on my back deck and built a square out of 2x6's and then put in 2x6 rafters spaced 2' apart. And it did sag just barely. It also has a metal roof.

[LD1]

The size post you need depends on how tall you make the building. If you only go 10' tall you could use 4x6 but I would use 6x6 in the corners. any taller I would use 6x6's all the way around. As to what size rafters you need depends on the pitch of the roof. The steeper the pitch, the smaller the rafter needs to be. IMO setting trusses on a larger building is easer than trying to set a ridge pole and rafters.

The spacing of the posts depends on a lot of things. 8 of 10 foot would work, but if you want garage doors larger than 8 foot, obviously that wont work. 8 foot is usually cheaper, even though you have to initally buy more posts, because most all dimensional lumber is cheaper by the foot if you buy 8 foot sections.

You also made mention about using electric poles. If your interested, shoot me your e-mail because I have a ton of pics of the 30x50 pole barn I am building and I used electric poles for mine. They are a lot cheaper(free) but they are a lot more time consuming to get everything squared up.