What size posts must I use for a pole building ?

[MARKTAKACS]

I am still in the research stages of making a pole building on my property that will by used for general storage and as a work shop. The size is going to be some where around 30'x40'x12' to 24'x30'x12'. I currently have a 16'x28'x9' pole building that I had no involvement in building, it has 4x4 post exery 8 feet and has been in service for 15+ years with no problems.
So on a larger pole building how do I determine what my post size should be (4x4, 4x6, 6x6). I know most would say the bigger the better, but if smaller would do it would seem nice to get by with using 4x4 for cost, ease of handling, and availability, especially lengths, but Iam still researching costs.
I have searched previous discussions and I have purchased the NRAES Post Frame building handbook and neither seem to discuss the issue.

Mark Takacs

[AndyF]

Take a look at chapter 2 of the NRAES book, "Design Considerations" It has a lot of good information that will point you in the correct direction for sizing your posts. Alternately, talk to 2 or 3 builders and see what they tell you.

My 24X40 barn with 12' sidewalls and a 7/12 pitch and rafters rather than trusses for the roof was built with 6X6 posts through out to accomodate the lofts built on both sides of the center bay.

[egon]

You may also check with local codes if they apply. The sizing may vary as to locality as snow and wind loading vary. It will also vary according to the length of the pole.

Egon

[Gatorboy]

You might want to build up your own 6x6's using 2x6's. Morton Buildings do this with their buildings.

Here is a couple shots of mine. This is the bottom portion -- pressure treated -- which will go into the ground. The upper portion would be build from non-treated wood -- much cheaper to do it this way than buying 6x6x12' treated posts. You can see how the bottom and top sections would be spliced together. Another plus to doing it this way, is at the top, you can make the middle section shorter so that your trusses can fit into a notch.

Photos: 1 | 2

This post was built from one 2x6x8 and two 2x6x12's.

[Stoneheartfarm]

My barn uses 4x6. I don't see too many that use 4x4, except storage buildings (we use these to make hay storage areas.) My experience with 4x4 and 6x6 is that they are usually straighter than 4x6, which tends to warp.

Steve

[ELEE]

I have built pole barns for years on my small farms in OH and WV. I also have worked at different lumber distributers and have a degree in forestry. That said things are changing all the time due to recent environmental laws on treatment of wood. as of January the 2x material has new preservatives as arsonic is phased out except for agriculture use. 4x6 and 6x6 area suppliers provide here is treated for underground use most places (.60) but 4x4 are only treated for above ground use (.40) and some distributors sell 4x6 and 6x6 only treated for above ground use without telling you or even knowing. 84 lumber in our area does this and charges just as much for the lower (.40) treated wood. Just look at the label fastened to the ends for the facts. If you can find a pole barn builder that sells to do it yourselfers he would have the 4x and 6 x treated for underground use.
The other consideration is the 6x6 per board foot often cost more per board foot than 4x6's so if you can engineer it with 4x6's even using more posts you can save money and have a stronger product.
Morton does use the 2x6 method because treating 4x6 or 6x6's with pressure wood preservitave does't get enough preservitave to the center of the thick pieces. That makes sense and I considered it but finding 2x6 's treated for underground use and and the cost of stainless steel fasteners they use plus all the labor makes it prohibitave.
I have always preferred 4x6's for cost and the deeper treatment than 6x6's if possible. morton used to have good brochure showing the deep treatment problems. I also copied the dry concrete mix to pack posts in they started and even some of the amish use. I am a poor typist and pardon the mistakes. I usually am just a reader on this list but due to recent knee surgury I now have time to type for a little while. Good luck with the barn.

[MARKTAKACS]

Dave, thanks for bringing up the method of engineering the post from 2x6's. I would greatly appreciate if you could give me some more info on your method of making the posts, as far as gluing, nailing, splicing, etc. ELEE, I have witnessed firsthand the lack of preservative in 6x6's, they split at the surface, water infiltrates, then it rots from the inside out (my retaining wall tops). I also like the blocking method, for setting the trusses on the the post. At first I thought that built-up posts would help me figure out how to get all the posts on their footings and come out near level on the top with each other, but I think this might be another posting! [img]/forums/images/icons/confused.gif[/img]

Finally.....I would hope someone might have some guidelines to answer my initial question about pole size requirements(4x4, 6x6) in relation to the building size. I know most would rather be safe than sorry, but could we be overdoing it with 6x6's.

Mark

[ELEE]

Well you can find charts showing the strength of particular boards but you may have to hire an architect to know for sure based on design of building,snow load in your area or wind shear. Or you could do what most do it yourselfers do -copy other plans like morton or some other engineered building company who puts up buildings in your area,neighbors buildings and when you feel experienced take your chances with your own plans. I tend to overbuild myself but depending on design ,bracing etc you can still use smaller materials. A lot of old plans are available online from http://www.ag.ndsu.nodak.edu/abeng/plans/index.htm and adapt them. they have been engineered by govt but you may have to adapt since some ,were done before treated yellow pine was available. The ones in blue are online. Have fun.

[egon]

If one is has concerns about buried wood rotting why not go to concrete piles and build and use wood for the above ground stuff.

Piles would make it much easier to line things up.

Egon

[Stoneheartfarm]

You could go to your local lumber yard and price out a barn kit. Ask for a list of what's included. It should specify the pole size.

Steve