Pole Building footings

[rimshot]

I'm thinking about doing a pole building this spring. I have some trees to get cut down an tops burned. With the snow still on ground now is a great time for that stuff. I'll dig stumps out when frost is out of the ground.

I'll settle on a size later but let's fiigure something like 28' X 32'. This size would be the top end of the scale and it might even be down around the 20' X 30' range. I want the building as storage only for my trailer and maybe the tractor during the warmer months. I'm not going to have a concrete floor because it will just be storage building back in the woods behind my house.

I suppose I would space 4" X 6" wolmanized posts on about 8' spacing as specified according to the layout. So that means I shall need some concrete footings dug. This ground is all nice gravel ranging from pea stone to perhaps 8-10" diameter stuff. Post augers just don't work well here so being I have a backhoe I think I will just dig a hole down at least 42" deep to satisfy the local depth requirements for footing depth. I won't be forming anything so using the hole dug with the backhoe I will see to it the sides will be squared up so that I can just pour a footing of roughly 12" diameter an six to eight inches thick to center post on. If I have to I can drive a simple stake and shoot the grade level of the top level of stake as I pound it down and use this level to signal the grade of the top of the footing. Placement of course will be established with building lines and batter boards.

When I get all the footings poured with a helper, we can stand the posts on end resting on the exact building line marked on footing and brace plumb an back fill with a shovel until post has gravel backfill back to grade. At this point I should be ready to start nailing up skirt boards, and 2 x 12" for eventual truss application. Any suggestions or comments will be appreciated.

I'm retired so I can take my time and complete this thing.

rimshot

 

[DiskDoctr]

Hi Rimshot,

When I put in the 40' x 60' steel building here, I used 24" wide sonatubes. These are basically a thick cardboard and I think some plastic maybe. Looks like a giant empty toilet paper roll.

Dug holes for each post with backhoe, inserted and stabilized tube (cut to size with sawzall), and then filled in around to support. Filled these with concrete to level about 4-6" below the expected finished floor level.

We poured the concrete floor over top of these (which I understand you won't be doing this step), then used "earthquake anchors" (big concrete anchor/lags) to fasten our plates to the floor. A good, large hammerdrill works well to drill the holes.

We didn't need quite 24", but the concrete supplier had these as part of a mistake order and I got a deal.

The building has up to nearly 8' of fill at one end and about 1' at the other and it has never moved or cracked. I have 2 expansion joints, making 3 sections of 20' x 40' (also used wire and fiberglass mixed in).

The point is the pillars worked extremely well, even though the holes weren't very round as dug with the hoe initially. Maybe they can work for you?

Have fun and put in lots of lights on separate banks. T8's are best. And lots of plugs!

Hope this helps!

- JC

 

[rimshot]

Howdy DiskDoctr,

I would think 24 " diameter sonotubes would make a good form for this project. I wasn't planning on using any hardware where post meets concrete however. Since I have to have 42" from grade to bottom of footing I'm thinking of using your sono tubes an cutting them about 10 height. Then I can see to it each hole is compacted and cleaned up with a shovel.

The tube will be placed centered on the pole and I can drive a rerod stake shooting the top level to grade of top of footing. If I place the concrete within the form an keep it a bit lower that the top of the form I'm going to pump it once and regardless if the tube/form is slightly out of level the concrete should level itself. The building vertical posts can than be placed in middle of footing and plummed too the building line.

With nearly three feet of backfilled gravel around the post it ought to stay there. This should eliminate any need for me to use any of the hardware you had to use. I have used this method for pouring footings before and it works well in the right type of soil and ditches cleaned up by hand shovel. I hope my posts are straight it seems like this wolmanized stuff can really take off in the sun.

Thanks for checking in.

rimshot

 

[Diamondpilot]

Around here they just dig a hole 48" deep with a post hole digger, pour in concrete 6" and let it set up. The corner post get full concrete along with any poles at door opening but the rest just get stuck in on top of the concrete pad then back filled with dirt and tamped in.

Chris

 

[bobodu]

Building inspector told me to fill with gravel as it allows water to weep out the bottom into the soil and that they no longer recommend cement because water settles around the bottom of the post. He said to nail small scraps of treated 2 x 4 near the bottom of the post to help prevent frost heave.

 

[rimshot]

It's kind of interesting to see so many variations different folks utilize. Using the concrete seems to hold some appeal for me if for no other reason than to serve to spread the weight. If a person took a 1 5/8" X 7 5/8 x 15 5/8 concrete block slab and cut it in half placing the cut block between footing and post he could get that post bottom up off the concrete footing and then the water damage would be minimized .

rimshot

 

[Duffster]

I wouldn't worry about water on the bottom of the post. Posts rot at ground level where they get water and air.

 

[DiskDoctr]

I wasn't planning on using any hardware where post meets concrete however.

Hey Rimshot,

You may want to reconsider this part. Buildings tend to sway and move with weight, wind, snow, frost, etc. They can also LIFT We don't often think about that here in NOT hurricane or frequent tornado strike country, but it does make a difference.

Some sort of bracket that would hold the bottom of the post in place and anchored to the concrete would definitely be recommended (maybe even required by code?)

I heard for the first time around here that in order to refinance a mobile home, my friends had to buy and install a cable and bracket tie down system before the loan would go through.

Just watching your back

- JC

 

[QRTRHRS]

Does your local code allow precast footings? Usually cheaper than bringing in the ready mix truck maybe not so if you have a mixer. Just tamp the ground first.

As suggested, you need to limit post uplift. For windy sites, put blocks on all four sides of the post. The blocks should be treated for ground contact. They should be the same width as the posts and about eight inches long. Predrill the holes else they will split over time. Galvanized angle iron will work as well but use stainless fasteners.

By the way, all of your fasteners should be rated for ACQ or CCA contact, which ever type of treated posts you are using.

 

[QRTRHRS]

Hey Rimshot,

You may want to reconsider this part. Buildings tend to sway and move with weight, wind, snow, frost, etc. They can also LIFT We don't often think about that here in NOT hurricane or frequent tornado strike country, but it does make a difference.

Some sort of bracket that would hold the bottom of the post in place and anchored to the concrete would definitely be recommended (maybe even required by code?)

I heard for the first time around here that in order to refinance a mobile home, my friends had to buy and install a cable and bracket tie down system before the loan would go through.

Just watching your back

- JC

I never heard of anyone using a bracket to secure a post to a concrete pad with polebarn construction? I have seen "L" shaped brackets holding post frames to concrete foundations.