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Old 09-07-2010, 04:38 PM   #1
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slab thickness

I have a area under a screen porch that I would like to cover and use for light storage... ie lawnmower, wheelbarrow nothing heavy. Can I get away with putting down 3 inches of concrete right over the dirt. I was thinking of using some Quikrete.... I live in NC so I do not have to worry a deep frost line, and since it is covered it will not be exposed to any elements, ie rain.
would it help if i put down a thin layer of gravel but then I am looking at only 2 inches of concrete? Or do I need to dig down and go with 4 inches of concrete? If 3 inches is good enought I am ready to start mixing but if I need to go thicker I will have to start digging

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Old 09-08-2010, 04:52 AM   #2
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personally, i'd just put crushed stone there like we did at our house in atl but, if you're set on conc, 3" is fine properly mixed, placed, finished, & cured,,, your slabs need to be smaller than if 4" thick but that's not a big deal,,, q/c-sackcrete-gawda'mightycrete is a good product - just don't add too much wtr,,, i'd think you're labor short if trying to do this by yourself.

you should have a compacted base w/good drainage but underdeck i'd probably do the same IF i/we wanted conc,,, good luck !
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Old 09-08-2010, 10:11 AM   #3
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I live in Boston and we put 6" of crush stone and 4" for slab, driveway 6"for slab .PS put roll plastic down under the stone thats what i would do
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Old 09-08-2010, 03:50 PM   #4
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thickness of your concrete has nothing to do with the possibilities of cracking. there are multiple variables, some of which you will have no control over. i have seen that the less you mess with the ground, the better chance you have with fighting cracks. i know of a place that had concrete poured out of a truck on the ground on average two inches thick and half-heartedly leveled that has supported large tractors in excess of 15 tons for close to twenty years now with no cracks.

You hired WHO?
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Old 09-11-2010, 01:46 AM   #5
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Standard concrete floor slab thickness in residential construction is 4. As for the concrete mix, it should be around 3000 psi.
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Old 09-11-2010, 08:05 AM   #6
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Thickness of concrete

As long as you get a reasonable surface for the concrete to be laid on and make sure that the soil is well wet prior to laying you should only need a 60 to 70mm base for light areas, make sure that once the concrete is laid you keep it moist, the more moisture that you have the stronger the concrete is in the end, they used to actually do the strength tests on concrete using concrete that had been allowed to set underwater, not sure if they still do this but that was the reason why (because it had a stronger finish).
Hope this is of help
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Old 09-11-2010, 08:39 AM   #7
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This is for light storage, NOT residential construction, so relax about the thickness etc. And so what if it cracks, do you really think the lawnmower is going to care? Personally I like the idea of three inches of crushed stone, cheap, flexible, but if you want the smooth surface, three inches of concrete is fine, no mesh, no reinforcing needed. The critical factor in appearance will be how carefully you finish the surface, but if you don't care about appearance, then have another beer and let it cure without any finishing at all.
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