subbase fill for pole barn slab

Buck455 · Sep 27, 2012

Hi all.

I'm looking for some advise on what material I should be using to bring up the grade underneath a future pole barn concrete slab. I'm building a 30x48 barn in southeast Michigan, and I have about a quarter of the area that tapers from 1' to 4' undergrade. Also, I have two trees to pull and fill.

Can anybody suggest what the proper fill material(s) should be to bring up the grade? My plan thus far is to remove the top 4-6 inches of sod and top soil, dig out the tree stump and roots, level what I can with a bobcat and compact, then bring in the fill.

Thoughs?

Thanks in advance!

gumshu · Sep 27, 2012

Depending on your terrain, you may need to cut a key-way to get proper compaction on whatever fill material you decide to use. There are a variety of fill materials you can use. Stay away from any top soil or dirt containing organic decomposition. Subsoil is probably cheapest and 95% compaction is typically adequate. You can use a "sheep's foot" or tractor to compact the moist soil.

BHD · Sep 27, 2012

I would most likely use gravel

LD1 · Sep 27, 2012

As gumshu said, sub-soil is probabally the cheapest. But it needs compacted somehow. That requires either a sheeps foot, or doing it an inch or two at a time and driving over the whole area with the SS or tractor before the next inch or two. Either that, or wait a few years for things to settle on their own before the pour.

IF neither of those is what you want, then gravel. Something like 304's (or what others call crusher run). But it will take alot. I figure about 80 yards just to make up the 3' difference in elevation. And about another 20 yards if you want 4" of base on top of that. So 100 yards, you are looking at about 150T of limestone or about 200T if you go gravel. Either way, you are looking at about $2000-$3000 of stone.

Two other options is either cut the whole hillside out down to virgin ground.....or

Only cut about half of the hillside out, and use that dirt to build up the lower half of the hillside. But again, you have to compact that lower section.

Buck455 · Sep 27, 2012

Thanks for the input guys. Sand is pretty cheap in this area, would that be a viable option for that much fill?

LD1 · Sep 27, 2012

Buck455 said:
Thanks for the input guys. Sand is pretty cheap in this area, would that be a viable option for that much fill?

No. I wouldnt use sand. Not unless you had a SOLID way to capture it to keep it from squishing/washing out from underneath the concrete.

Would you pour a concrete slab on a beach and expect to to hold up to driving on without cracking??

Buck455 · Sep 27, 2012

That's fair. I will be backfilling at least 5' around the barn with sub soil/topsoil.

DJ54 · Sep 27, 2012

Are there any gravel banks near you..?? Such as like Bank Run gravel..?? That's what I used for my two new buildings I just had put up. Put it in in 8" lifts,and rolled 3 times with my Massey 180 with a carry-all on back with all that would stick on there. I hit a decent seam of yellow clay, so mixed it @ about 30%. When I backed in with my 1 ton dump, with approx. 4 tons on, it just left a tire print, and it did not sink in. When they dug the holes for the poles, they used a Bobcat with an auger w/an aggresive bit. He had to rear back on the auger to dig the holes... Last Friday when my buddy poured the floor for my new shop, he had to use a 5 lb. sledge to drive in 1" steel form pins. I'm pretty confident it's not going anywhere.

Not sure what you native soil is below the topsoil, but if there is some shaley clay, that is excellent fill, if you have a knob you can strip the topsoil from, then remove enough clay to fill, then reclaim the area.

nybirdman · Sep 27, 2012

We are in the process of doing a pole barn ourselves(my son-in -law) and he is an engineer.Removed the top soil and leveled with my tractor/box blade.Bringing in "crusher-run underneath.30x40x12.Estimated cost of $9,000 plus the stone which will be about $350/20 ton loads.Planning on concrete in one bay next year.