I am in the planning stages of a pole barn. It looks like I need around 20" of fill to get to same grade as house/garage. How much sod do I need to peel off? I will be filling with sand. I have clay but haven't dug to see how far down. I'm in Michigan and I'm guessing the clay is near the frost line. Thanks. -MATT
excavating question
- Thread starter matt60j
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boiler7904
Well-known member
You need to remove all sod and other organic material like top soil / black dirt. Over time, they will decompose and your slab will drop.
A vein of clay can be anywhere from a couple of inches deep to several feet or more. As long as it has a decent bearing capacity, you can leave the clay and fill on top of it.
Make sure you compact the fill sand in lifts or layers between 6 and 8" deep.
A vein of clay can be anywhere from a couple of inches deep to several feet or more. As long as it has a decent bearing capacity, you can leave the clay and fill on top of it.
Make sure you compact the fill sand in lifts or layers between 6 and 8" deep.
Boiler is pretty much right.
If it is black, you don't want it nder a slab that will have any kind of weight on it. the lightness of it that makes it so good to grow things in also means it will compact under load. And then your slab cracks ot tilts.
Dig it out, pile it up and sell it for lawns. That way you can buy the sand and gravel you need under your slab.
If it is black, you don't want it nder a slab that will have any kind of weight on it. the lightness of it that makes it so good to grow things in also means it will compact under load. And then your slab cracks ot tilts.
Dig it out, pile it up and sell it for lawns. That way you can buy the sand and gravel you need under your slab.
Quebec Bob
New member
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- Aug 29, 2006
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In part, what you are looking to do by removing any organic matter is to remove anything that will hold moisture and therefore frost, one of the biggest killers of slabs when it lifts. It isn't necessary to go down 4 feet. Our climate here is similar to yours and we usually go down around a foot for the moisture reason above. I just dug a shop in my barn and went down two feet because it was indoors and had within the accumulation of a century of old deposits like timber, straw and hay. I removed the extra foot because of this organic material. The cement contractor was surprised that I had gone down the extra foot saying it wasn't really necessary but that it was still a good job done. Hope this helps.
Vicious_Cycle
Well-known member
My preference is to take it down to the clay. Topsoil doesn't make good base.
trovato
Well-known member
I wish I lived someplace where too much topsoil was a problem. Around here, if you don't truck in the topsoil, your lawn is growing in pebbles and rocks.
You should remove all organic materials down to undisturbed native soil.
Why are you using such an expensive backfill material such as sand? I would suggest a much cheaper well graded 1" gravel or similar structural fill in two or three compacted lifts. Lift thickness will depend on what type of compaction equipment you have.
If the native soils are clay you can also bring up the grade to the sub-base (just below gravels) elevation with clay, but this is extremely hard to compact in a residential "do it yourself" environment. Improperly compacted clays will almost certainly settle since they contain many voids.
It is best to go with a structural fill material .
Why are you using such an expensive backfill material such as sand? I would suggest a much cheaper well graded 1" gravel or similar structural fill in two or three compacted lifts. Lift thickness will depend on what type of compaction equipment you have.
If the native soils are clay you can also bring up the grade to the sub-base (just below gravels) elevation with clay, but this is extremely hard to compact in a residential "do it yourself" environment. Improperly compacted clays will almost certainly settle since they contain many voids.
It is best to go with a structural fill material .
snorvet
Well-known member
I agree that you have to get down to the clay. But before getting too excited, I would dig down to see where the clay actually is. Then you can get ideas on what you need to do to remove the bad material and bring the pad up to grade with a good base.
4' of unstable material sounds a little extreme for around here.
4' of unstable material sounds a little extreme for around here.
Call me at: 603-664-2347 I've been doing sitework for 20+ years. I'll answer all of your questions. Bryan
