Setting Poles for a pole barn “addition”

[Zaffer]

I have posted about repairing/replacing poles in one of my existing structures, but I’ve decided to do something else beforehand so I have a place to store everything while the repairs are taking place.

I need to remove part of my existing garage, an addition that is 8’x16’ and rotted out. Rather than replacing with similar, I am going to extend it to 14’x24’ and have it as a “stand alone” structure, but have the inside wall attached to the existing garage space as I figure it’ll add rigidity to everything. I’ll have 6x6’s at the corners and 4x6’s in between at 8’ OC.

My main question is what is a good way to build the foundation/footers/backfill for the posts? I am using GC pressure treated posts that are .60 CCA from a local yard and I will bury them 3’ in the ground. I live in western Piedmont area of VA.

I’ve looked into several options and I’m trying to figure out something that is good, but not overly expensive. My first inclination is to dig the hole, pour an 8”-10” thick layer of concrete (if that’s even necessary), set the pole on top after concrete sets up, and backfill with dirt, compacting it every 3”-4”. I’m not looking for it to last till the end of time, just limit/eliminate settling as I know it’ll outlast me by a long shot regardless. The space will have a pad poured inside as well, but the concrete will not envelope the posts.

Thanks for any advice and if something is not necessary or is missing, please let me know.

 

[kbs2244]

use tamped stone at the bottom of the hokes instead of concrete
you need the drainage it provides

for backfill use tamped stone for the first 6 inches, then 6 inches of tamped dirt
alternate the stone and dirt. tamping well

 

[Zaffer]

How large of a hole should I dig for the footing? Everything I’m seeing says 24” in diameter and at least 6”-8” thick. Is this necessary? My neighbor has a 1’ auger for his tractor. Should this suffice? It does a hell of a job for my fence posts.

 

[Zaffer]

I’ve been doing a little reading on what to use for poles and one thing that concerns me is using a solid PT 6x6 due to the possibility of warping/twisting. Would it be better for me to build laminated posts using 2x6’s? Or should I get the solid posts, let them dry in my garage, and swap out the ones that twist/warp? The yard I would be getting them from is pretty good and is a smaller family owned place that mills their boards on site.

 

[billconner]

I'd buy laminated posts and would try to find UC4C which is probably .80 pcf CCA, rather than UC4B at .60 pcf. And only the underground portion of the post needs treatment.

If you laminate yourself, would you use urea formaldehyde adhesive or moisture cured polyurethane? Finger joint the end to end splices? Interesting.

 

[Zaffer]

What I was thinking of doing would be to get 2x6x16 pressure treated boards then glue and screw them together, alternating the crowns to minimize warping, to form a 6x6. Cost would be about the same as a solid 6x6, but twisting would be a non-issue and I could plane any warping out. Just a thought as an alternative.

 

[Benny Franklin]

Red cedar posts, cut to length with the bark still on. My grandfather built sheds and barns this way in the 1990s and we're still using them

 

[Zaffer]

I’m still leaning towards the PT’s with .60 CCA posts due to simplicity and speed of install. Even those won’t rot for decades!

Concerning the footer, would gravel be the best option? I’m sure drainage would be good, but wouldn’t there still possibly be settling issues, or would I just use the same stone, compacted, as what’ll be under the concrete slab? What would be a good way to compact it and what size hole should it be? I’m leaning towards a hole one foot in diameter as that’s the size of the auger bit, but would wider be necessary? Lots of differing opinions out there.

 

[73fxe]

A 12" hole with a concrete puck in the bottom of the hole then set your post on it.

 

[theoldwizard1]

The absolute BEST foundation for post and beam is a 24" hole down to below the frost line (I would go at least 24" deep where there is no frost). Use a sonotube and set the height about 2"-4" above the finish grade. Fill with concrete. Set galvanized post bases in the "wet" concrete.

Second best,

A 12" hole with a concrete puck in the bottom of the hole then set your post on it.

Back fill with gravel for drainage away from the post.

 

[Zaffer]

I’ll be going 36” down for the post and then put the footer below that.

What about 2 - 80lb. bags of 4,000 psi concrete in the bottom of the hole, mixed and then poured in? That would form the footer to hole and, IMO, be better than the puck, which I can’t find around here.

Concerning the gravel backfill, wouldn’t that allow the pole to move? I read somewhere on here to alternate between gravel and dirt, compacting each level. And what gravel, 57 with fines, 57 without fines, crush and run?

 

[Bert_]

I've never seen concrete at the bottom of the hole for a pole building.

Way to much thought going into this for a little building. Just dig the hole, set the posts, and tamp the dirt as you backfill. Gravel will help the post last better

My opinion is if you're going to pour concrete, just dig a trench footing and stick build on top of it