Depth of Pole Barn Posts?

[Beltzington]

After a considerable amount of research, I believe I'm going with buried posts instead of cement piers. What I can't seem to get a bead on is how deep to set the posts. I have read 1/2 their heights, 1/3 of their height, 4-foot is more than enough. Since there is no frost-line in my area, I am only concerned with the minimum depth for a secure structure. Aprox details are:
Barn 16'W by 36'L
6" by 6" poles need to reach 16' above grade and will be set on 8' centers.
Idea is to build the center part of the barn first and add the side shed roofs later. Another TNB member built very similar project years ago but it seems he has left. Attached is PualT's barn that shows what I have in mind except I plan on extending the posts all the way to the roof.

 

[sal64]

my pole barn i buried the poles 4ft deep on a small concreet slad that was coed in my area. u should put a flat rock at bottom of post so post dosnt sink.

 

[DennisArrow]

For me, with a 16' above grade height, I would go 4' deep........A 2' diameter hole......Creosote, treat the below grade of the posts.........Set the posts on a bed of large rock/gravel.........Fill the hole up with concrete to just above grade and taper that down to grade, perhaps an inch high..............

Make sure you have some strings run and or a laser to check that the posts are plumb and in line with one another and YOU have it...........

Sounds like you are on the right road.........Good luck......Dennis

 

[Mickey_Fx]

Think depth will vary with soil conditions. If memory serves me right, I recall we dug 4' deep holes and put a ft of pea gravel in the bottom and set the post on top that. Filled the rest of the hole up to ~1ft level with gravel as well. Didn't fill the holes up very far until we had the posts positioned and vert. Once postion was final, then finished filling the holes.

Barn has been up for >30 yrs and doesn't appear that any of the posts have moved.

 

[winston1]

I've build several bldgs. similar to your pictures Between 2 and 3 ft is plenty deep. Have drilled holes and slipped re-bar thru same length as hole diameter to hold post from going down. Your siding, roofing, etc is what gives you strength. Most treated 4 x 4s or 6 x 6s would warp to high heaven if not tied and braced together with structure. I'm sure this will be jumped on but that's OK. This is my opinion based on experience. I am talking about cementing the posts in the ground.

 

[carpenter383]

I've build several bldgs. similar to your pictures Between 2 and 3 ft is plenty deep. Have drilled holes and slipped re-bar thru same length as hole diameter to hold post from going down. Your siding, roofing, etc is what gives you strength. Most treated 4 x 4s or 6 x 6s would warp to high heaven if not tied and braced together with structure. I'm sure this will be jumped on but that's OK. This is my opinion based on experience. I am talking about cementing the posts in the ground.

I agree 2-3ft deep with concrete around the post should be plenty (2ft if it's not too sandy or any chance of water wash out) Think about how much force it would take to move a post sideways that's 2ft in the ground. (while keeping it level) The roof and siding should take the racking forces, not the depth of the post.
They sell pre built sheds, small cabins, mobile homes, etc that are free standing with no posts/foundation. The bottom of the walls get their strength from the floor.

 

[timswi]

4ft on mine with a concrete base...Packed the original dirt above that.

 

[whistlepig]

4' deep with a concrete pad at the bottom. That was building code where we lived before. I had another barn built when we moved here by the same builder (Blitz). They did it the same way. 4' deep with a concrete pad at the bottom.

 

[keegs]

After a considerable amount of research, I believe I'm going with buried posts instead of cement piers. What I can't seem to get a bead on is how deep to set the posts. I have read 1/2 their heights, 1/3 of their height, 4-foot is more than enough. Since there is no frost-line in my area, I am only concerned with the minimum depth for a secure structure. Aprox details are:
Barn 16'W by 36'L
6" by 6" poles need to reach 16' above grade and will be set on 8' centers.
Idea is to build the center part of the barn first and add the side shed roofs later. Another TNB member built very similar project years ago but it seems he has left. Attached is PualT's barn that shows what I have in mind except I plan on extending the posts all the way to the roof.

That's one handsome pole barn Beltz...

If we get past this recession without too much damage, I'm going to have one built just like. If you don't mind me asking, is that a second floor hay loft?

 

[rgood]

4 feet