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Gravel Compaction under Conc Slab Floor
I plan on building a polebarn this spring. I plan on doing the base-prep myself with a box scraper and loader. I will be stripping 8”-12” of topsoil then replacing with gravel. My question is how to compact the gravel. Since I don’t have a vibratory roller handy, anyone have any suggestions on how to do this? After its compacted, I plan on placing some stone then pouring a concrete slab. Thanks.
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Gravel Compaction under Conc Slab Floor
It would depend on your soil type, If it's good drainage soil you could remove 8 12" of soil and put in 18 to 24" of Inch-minus without binder. The pad would need to be made 4 to 6 feet larger all around then the size of the slab. The only substitute for compaction with a machine that I know of would be make the pad, put a sprinkler system on it for a few weeks and then let it sit for a yr.
If your soil doesn't drain well, I would remove 18 to 24" of soil and replace it with 2" stone with drain swales at two Conner's on the down sloping side. Then place the 18 to 24" of Inch-minus without binder on top of that and make the pad a minimum of 10' larger than the size of the slab.
David
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Gravel Compaction under Conc Slab Floor
You can rent a wacker walk behind type. I would use a 600lb
machine at a min. go over it several times.
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Gravel Compaction under Conc Slab Floor
IMO and this is from experiance!!! THE MORE GROUND YOU REMOVE, THE MORE MONEY IN GRAVEL YOU MAY HAVE. Take a real good look at your GRADE before you remove existing ground. Shoot your grade first. You probably want that building UP atleast a foot and more than likely 18" or more.
I had a side hill where I put my garage. For what ever dumb reason I removed (dozed) it flat and did NOT level with the removed soil. Thinking I was going to swale it. a year later and 100 yards of gravel, I realized I messed up. I now have over 3 feet of gravel on the south side of the garage and 2 feet on the North. The garage is 34x28 and the area I had to re-raise is almost 1 1/2 time that big. I had to bring in almost 250 MORE yards of gravel. grand total 350 yards. If I would of let it lay I would of needed less than half that.
Anouther suggestion (and this may not be feesable anymore) If anyone is planning a garage. Bring the gravel base in a year or so early. I had on winter on half the gravel and anouther winter on the other half. This allowed it to settle real nice. Still had to raise one side up so I went with extra thick crete and extra re-bar.
If your going to use a tamper, lat half of your gravel and tamp it. then lay the rest and do it again. If time permits do it in 1/3's three times. You can never have fresh gravel compacted too much.
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Gravel Compaction under Conc Slab Floor
So I guess I should probably just have it leveled and compacted by someone with a roller. My barn will be 24x36 and I assume Ill prep a 28x40 area for it. My plan is to remove 8 to 12 inches of topsoil and replace with 12 to 14 inches of gravel. Then compact, then add 4" clean stone drained with some 4" perf. pipe, then add 5" conc slab on top. By this time I think ill be sufficiently above the surrounding grade. I dont think there is any way to avoid gravel cost. Brokenarrow.... sounds like you had the right idea but just maybe bumped it up a little to higher than you needed by maybe a foot. You could have probably gotten away with 6-12 inches on the high side rather than 2 ft., but I wouldn't regret using the gravel over the soil (assuming I understood you correctly) Thanks.
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Gravel Compaction under Conc Slab Floor
My real problem came with the garage being on a slope (side slope). With 3-4 feet of snow in some years, the melting and runnoff needed to be addressed.
MacDaddy, you sure that 24x36 is large enough for you? I found out that I really need about 36x36 to be able to comfortably turn and move impliments in the garage with the tractor and fel attatched. Mine is 28x34 and I knew I should of gone WIDER but at the time the tractor was not in my plans. If I was to do it again (which I may sooner than later) I will not build less than 36x36. I know funds are always a top priority. Much cheaper to wait a year and build larger that to not build big enough (man I wish I would of practiced what I am preaching  )
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Gravel Compaction under Conc Slab Floor
brokenarrow, your point is well taken. You're right, but Im really at my financial limit with the barn at its current size plus the tractor i've bought to put inside. I do have a 12x18 covered-bay in addition to the barn itself. This is where I plan to store the implements. There really is not much room to manuver in the barn b/c of the middle posts... unfortunately, its not going to be clear-span (again.. too much $$). Thanks for the input.
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Gravel Compaction under Conc Slab Floor
The covered bay will come in handy!!! Wish I had one. Good luck!
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Gravel Compaction under Conc Slab Floor
Had to add my reply here. I work in a Soils mechanics laboratory. We determine what compaction is needed and the rate of settlement on construction projects. Depnding on the lay of the land, and your soil type you may not need to get rid of 8'10" of soil. First and foremost is to correct any drainage problems before starting on your pad.
You may have to ditch or trench to redirect the water away from your pad. Save this material. Now remove your top soil with any organic material from the pad area. You can build up your pad area with soil (cheaper than gravel) (any soil as long as it doesn't contain organics). I would suggest using a plate tamper here you can rent one faily cheap. Compact in layers(lifts) no greater than 2-4". Sprinkle with water as you compact. the water addds in achieving maximum density. I would suggest using a landscape fabric on top of your earthen pad. Now you can add your gravel here. A word of caution, You do not want a pourous pad under your concrte when you pour. The water will drain out of the concrete from the under side and be weak. You should have enough fine material to compact your top layer very hard. THe organic topsoil you removed from the pad area can now be used around your pad to achieve the proper grade for drainage away from the base. Plastic can be added added underneath the slab before the pour. This will help your slab cure slowly. If you do a monolithic slab my suggestion would be to use rebaron the edges and thicker members. When curing your pad, let it dry slowly. Concrete reaches maximum strength in 28 days. The greatest strength is achieved in the first 5 days. Don't use any deicing salts on concrete for the first year or it will spall. Sorry about the long post but I really like to see a job well done that looks good and last forever. Most concrete cracking can be attributed to drying to quickly or a poor foundation (not enough compaction). You tractor doesn't exert enough compaction if you are more than 4 inches thick. Use a plate tamper, you won't be sorry.
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Gravel Compaction under Conc Slab Floor
Address the elevation and drainage issues before building the building not after.
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