So... what size slab would you recommend pouring (full length of course, 20'x'15') ? Thickness that is.
Is this a hire it out job considering I'm relatively clueless about this?
What might this run me? I can handle digging/ levelling/ tamping.
I'm in Mass, so we have frost heave... does this also require a proper footing? Yeah I know, ask the building inspector...
And finally, is it worth it?
-Craig
Yes, you can do it yourself. The hard part will be finishing it when you pour. You will need a few hard working hands to help you and the proper tools (which you can get at most rental yards). You will want more labor, if you are short and the concrete sets up too early on you, there is no turning back.
I tend to over-do things when they are for myself. So keep that in mind here. Prices are from around here.
1. You do not need a standard footer if your are not supporting any vertical structures on the concrete. You can put in column footers first and then pour a slab later. If you do this, you do not want to tie the slab into these footers. The column footers, assuming they are are installed to frost depth, will not move with freezing/thawing, but your slab will.
*I would, but not necessary, install a frost footer. Typically, this is down to frost line, 6-8" wide at the bottom. At most, one run of rebar. This will be poured monolithic with your slab.
2. I like clean aggregate for my subbase. You would only need 4" for a shed slab. I would install 6 if it were me though. Keeping moisture from standing below your slab is key to keep from uneven heaving. (7-8 tons, I would order extra as a backfill border around the shed rather than backfilling with topsoil straight up to your structure. $200)
3. I would install a 10mil vapor barrier. Some might not think it is needed in an unheated structure. But I like it cause it will help keeping moisture from forming on days of extreme temperature change. You are only building a shed, so just get some 10 mil plastic from a hardware store. ($200)
4. 4" concrete minimum. I like to use 4,000 psi concrete. This would take 4 cubic yards. You are going to pay a flat rate for the truck, then per yard for concrete. ($530). If you are going to install frost footer, just figure out your volume and add your per cy price since you will pour all at the same time anyway. You could use wire mesh to reinforce the slab if you are going to running a larger tractor in the shed. ($75) I like to use 5" thick concrete if I am using wire. ($600)
5. If possible, elevate the bottom of your slab so it is slightly above the surrounding grade. This just helps with keeping water from collecting under the slab.
Hope this helps, good luck.