Ok I am curious which is best for a roof rafters or roof trusses when building a pole barn and also is it best to dick your hole for your post and fill with concrete and let it set and attach the post to the concrete or is it best to put the post into the ground with concrete around them I live in Ky if that helps any oh I plan on building my pole barn atleast 32'x40'
Thanks
For a 32' wide barn, you'll need rafters longer than 16', closer to 18 or 20' if you have an overhang and depending on the slope of your roof.
Opinions differ but putting concrete around the posts is not a good idea, imo. Use gravel to drain the water from around the post. Also, putting the post on top of a concrete pier will require hardware and consideration must be given to the loss of lateral stability that comes from having the posts in the ground. I.e. need to have bracing to keep the walls from falling over. An open interior barn with rafters and posts set on concrete piers is a poor design, imo. Don't think it would take much to push it over.
IMHO, it depends on the intended barn use. If we are talking a storage barn, etc. then I would use trusses. For a horse barn, I would use rafters. Mostly, horse barns mean stalls which mean corner posts. Visualize this. Lay out your barn with three long bays as viewed from and end wall. Let's say this is going to be a 36' wide barn. So, when you set your posts, you have 12' spacing between four rows of posts. You run headers on all four rows of posts. The two center rows of posts are connected by a twelve foot piece of 2x? (collar tie). Then, the rafters are laid on the headers and with a single header at the very top. Similar to stick built house construction.
The logic behind a basic pole barn is to bury the post to resist wind loads. Concreting the posts or not is a matter of discussion as well as location. The concrete must be poured around a post already placed on a prexisting pad so there is seam to allow drainage.
You should have a footer for each post. You can pour concrete or use precast round pads on the tamped dirt in your post hole. Concrete or not, you need some kind of mechinism to resist uplift. Either ~8" PT plates secured to your posts or galvanized angle iron will do.
I admit that I do not know squat about ACQ treated posts. I only know about the CCA posts which were rated by % of retention. IE; .40, .60, .80, etc. CCA treated posts must be at least .60 or they definately will rot, concrete or not.
You can purchase plastic sleeves for your posts. They are slipped over the post prior to placement in the hole. I have heard good and bad about them as well. Moisture is moisture.
If the building is something long term such as a church or if budget is flexible, consider Permacolumns. (Do a search). They will add ~25% to your post cost.
With ACQ or CCA treated wood, use rated hardware for everyboard that touches the treated wood.
The only real "safe" method of roof construction is prefabricated roof trusses (unless you have very minimal spans). It is also best to dig the post holes, set the post to the bottom of the hole and backfill around it with concrete. Provided your holes are of adequate diameter and you use enough concrete, this will resist over turning, settlement and uplift forces.
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