Best base material for post frame concrete slab?

[Jay13]

I live in a frost area and have heard several different options on base material for the concrete floor but what works best? I just talked to a reputable builder that said if its a dry area to put down bank sand and if its a wet area prone to holding water to use pea gravel. I heard #57 limestone was good from someone else but he said it doesn't compact well and is not ideal. Reading the internet makes it more confusing and people seem to use many different materials for a base. I scraped off the vegetation and will add enough fill and grade away from the garage for water run off. I understand the importance of keeping water away but what is a preferred base material?

 

[classic boost]

just vegetation or topsoil too? #57 compacts fine.

 

[Marctrees]

I am not a dirt or concrete guy, but different geo areas have different "fill" available.

I'ts all about compactability of what you have available. Marc

 

[theoldwizard1]

You do NOT want "pea" gravel ! And round/smooth gravel will not compact well. Crushed limestone compacts very well. "Crusher run" (goes by different names in different parts of the country) is a mixture of 3/4" and down. It compacts very well. It will hold up to a bit of vehicle traffic as long as they are not too heavy. You can always add a bit of stone dust over the top and re-compact years later.

I would concur with the rest of what the contractor said. Dry area, use sand, Wet, use gravel.

 

[Jay13]

just vegetation or topsoil too? #57 compacts fine.

Some topsoil. I know topsoil is not ideal but id have to dig out another 2+ feet to get it all out. Its kind of a mix of dirt and topsoil, but its packed like concrete from running the tractor on it for several hours.

 

[mmb617]

I'm in central PA so I'd guess our climate is similar to yours in Ohio. I used the #57 limestone (it's called 2B here) under my garage floor. It's been up for 14 years so far and no problems with the concrete.

 

[kbs2244]

It is not the weather so much as it is the dirt.
And that can change from lot to lot let alone state to state,
Go with what a good, established, local concrete guys says.
It is his reputation he is pouring.

 

[PugetDude]

Another vote for well-compacted Crusher Run.

 

[Bondo]

I scraped off the vegetation and will add enough fill and grade away from the garage for water run off. I understand the importance of keeping water away but what is a preferred base material?
Some topsoil. I know topsoil is not ideal but id have to dig out another 2+ feet to get it all out. Its kind of a mix of dirt and topsoil, but its packed like concrete from running the tractor on it for several hours.

Ayuh,.... An important Trick of the trade,....
Make sure yer sub-grade is pitched slightly so it's self-drainin',...

Then build yer pad outa crusher run gravel, compacted in small lifts,...
Limestone is the choice 'round here, 3/4" minus,....

Once grade is set, slope away from the buildin' pad,...

If the water can't get under it, as it drains away, there's no water to freeze, 'n heave,...

For questionable sub-grade soils, Geo-textiles should be considered, under the stone,...

 

[dneiding]

I used asphalt road grindings. Cheep and compacts really, really good.

 

[Jay13]

I used asphalt road grindings. Cheep and compacts really, really good.

I thought about using grindings but never heard of anyone using them under concrete. I just put them down for a driveway to the garage and I agree they compact well and are easy to spread. How long ago did you pour on them? How is it holding up?

 

[Orionrising]

I thought about using grindings but never heard of anyone using them under concrete. I just put them down for a driveway to the garage and I agree they compact well and are easy to spread. How long ago did you pour on them? How is it holding up?

this may depend on local rock availability. around here rock is cheap and plentiful, grindings less so, so gindings would cost about 25% more then crush

 

[tomralph]

I used crushed concrete from a local recycler. Same 3/4" minus as a crusher run, but got it for dollars a ton. Did 4" lifts with a jumping jack, then a 2" lift a few months later (after a few wet and heavy snows) with a plate compactor, then a 4" list a week later with a roller.

We did get some setteling in one corner with the snow on it, maybe a 1/2" of movement. I think we did it right by lifting it in the fall, and letting winter happen on it, plus using it as a parking lot anytime anyone came over to help any setteling before we build on it next week.

 

[matt_i]

I used crushed concrete from a local recycler. Same 3/4" minus as a crusher run, but got it for dollars a ton. Did 4" lifts with a jumping jack, then a 2" lift a few months later (after a few wet and heavy snows) with a plate compactor, then a 4" list a week later with a roller.

We did get some setteling in one corner with the snow on it, maybe a 1/2" of movement. I think we did it right by lifting it in the fall, and letting winter happen on it, plus using it as a parking lot anytime anyone came over to help any setteling before we build on it next week.

That's how I would use crusher run. Let it sit outside for months to allow the fines to compact more with the aid of water.

If you want to place, pack, and pour then use #57 (washed) as it won't ever compact any more if the subgrade is solid...