|
Eel-eater, I had the same questions when I poured my floor. I did a fair amount of research, and here's what I came up with. Unfortunately, my floor hasn't seen much use, so I can only speculate on how well it's going to hold up. First, you need to use insulation rated at 25 psi compressive strength minimum (the Home Depot stuff is only 15 psi). Higher strength insulation is available, but is probably special order and not worth the expense unless you plan to have really heavy loads (e.g. big crawler tractors). You should use at least two inches under the outer 2 to 4 feet of the slab, one inch will be sufficient for the interior of the slab. It is very important to insulate the vertical edges of the slab, this is where much of the heat loss will be. Use at least 2 inch insulation; you can cut the insulation at a 45 degree angle so the concrete will taper toward the outer edge. A Skil saw or table saw works good for ripping the insulation, by the way. An alternative to insulating under the slap is to only insulate the vertical edges. So if you need a 2' ratwall (required by many codes), use 2 inch insulation inside the ratwall form. You can eliminate the insulation under the slab, which will save money and should result in a stronger floor. You sholdn't go this way if your ground is real wet. I went with 3500 psi concrete. I think this is about the minimum anyone should use for a shop floor. Obviously, either rebar or steel mesh is required. I used mesh, but it's so much aggravation I would be tempted to use rebar in the future. Since I poured my slab in sections, I tied the sections together with short pieces of 1/2" rebar. I got my PEX tubing from Mountain View Supply (www.mvsupply.biz). They included a real good manual from Vanguard Pipe titled "Design and Installation Manual. You should be able to get a copy from MV Supply or directly from Vanguard (www.vanguardpipe.com).
| 
