Best Substrate for Concrete

[barnjunkie]

I currently have a 40x60 pole barn with a dirt floor. What is the best way to prepare the building for a concrete pad? I've heard a lot of recommendations, but I want something that will create the least amount of problems in the future.
My soil quality is mostly clay (which turns into a sticky cake when wet) and really gets muddy around the edges when it rains.

 

[dw1]

We graded out about 20 tons of # 57's in and out in front of my 30x48 last week, I ran the tamper to compact it. I left the doors and windows open to circulate air, it dried out pretty good, everything is tight. I put a 6 mil plastic vapor barrier down yesterday, waiting on my concrete guy now, suppose to rain the next few days.

This was kind of a "Touch Up" my pole barn was built on a gravel pad that we made last summer for this.

 

[RivennHewn]

I'd suggest removing any native soil that has turned to mud, and replace with crushed rock.

I'd also suggest getting down to undisturbed native soil, then building back up with a layer of larger crushed like 1-1/4" then finish with 5/8" with fines in it.

 

[bmxdad]

How long has it been covered? All clay or is there anything else mixed in it?

How deep would the floor be if concrete was poured now?

 

[barnjunkie]

It has been covered about 6 months, but water infiltrates in because the middle is a few inches lowr than the edges. I was really looking for suggestions to help fill.
I think dw1 is right on, I definitely need a vapor barrier. The soil is amost all clay and maybe some silt (its on a slght hill).
I was personally thinking of using crusher run and putting a 10 mil plastic sheet down before pouring.

 

[theoldwizard1]

I would definitely remove at least remove 6-8" of the existing soil.

Around here they usually use sand because it is cheap. If you use gravel the first 4" can be "mixed" grade (different names in different parts of the country), but the final 2-4" should be "stone dust" (also called 'slag"; very fine crushed stone).

What ever you use, it must be compacted in 4" lifts.

 

[Garage Flooring]

I'm not a foundation guy and it sounds like you are getting some great advice. I had a horrible experience with a specific type of clay that can be present in one lot and not another.

Do your homework on your local conditions too. It could have cost us everything has ours not been modified.

 

[Angelfire]

Over excavate and backfill with base course suitable for your area. Compact it in small lifts as you fill and you will have a very stable floor.

 

[MagKarl]

I would fix the exterior grading to address the runoff/interior pooling problem first. You want that ground dry and stable long term. We use compacted crushed rock around here for concrete substrate.

 

[dw1]

I would fix the exterior grading to address the runoff/interior pooling problem first. You want that ground dry and stable long term. We use compacted crushed rock around here for concrete substrate.

Luckily my buddy owns an excavating company, he pointed out all my drainage/runoff issues, we ended up cutting a drainage swale on two sides of my building by my property line, before we started building up the pad for it to sit on. I also ran my downspouts into a 4" underground SDR pipe to get rid of the water. As stated above, I would try to get rid (divert it before it can get to your building) any water running issues.

We have had abput 14" of rain here in the last two weeks, other than washing 50# of grass seed down the hill, I have not had any water issues entering my building.