Concrete garage floor reinforcing

	I am building a 1500 sf garage and want to install a heated floor system in it. My concrete contractor wants to use a two foot square re-bar grid and my heated floor contractor wants to use sheets of wire mesh. They both agree either system would work but they want me to be the deciding factor. It's my understanding re-bar would be stronger but wire mesh would work. Can you help me with this decision? I live in the mid-west, so mother nature may be a factor, it can be 100 in the summer and -40 in the winter. Glenwood, USA
	This is a pretty big garage. The key here is to create joints every 12-15 feet. Otherwise, it is practically guaranteed that you will have cracks. It is also important to pour the slab separate from the stem wall / footings so that it can move and shrink freely - what is called a "floating" slab. Once you got that, either option is acceptable. You need to understand that wire-mesh does NOT contribute anything to the strength of the slab. If the soil is expansive, or you have soil settlements, the rebar will help the slab survive some movements. The wire-mesh will not. Both will work to minimize cracking in the slab, as long as the joints are installed properly. One problem with rebar is that it can interfere with the joints function by bridging the joints and actually allowing cracks to develop outside the joints. However, as long as the rebars are uniformly placed and properly over-lapped it should by fine. A big problem with wire-mesh is that it rarely stays where it is supposed to be (centered in the slab) because laborers walk over it during pouring and it might end-up in the bottom of the slab where it is useless. Rebars are placed on "chairs" that support them in the right position, and the 2 feet spacing allows people to walk in the work area without stepping on the rebars. Bottom line - rebar requires a little more work from the contractor, but is likely to result in a better final product.
	Thank You for this information, I think I will go with re-bar. I do have another small problem I hope you will be able to help me with. My heating contractor says I need to install some sort of insulation between the concrete floor and the outside walls to prevent heat loss. He suggested using high density foam insulation. But my concrete contractor has never done this before and is concerned the foam will be exposed into the working area of the garage and will be susceptible to damage and water. Is there a good solution to this problem?
	High density foam would be an acceptable choice as far as the concrete is concerned. It would be best if you keep it to no more than 1/2" thickness. However, this 1/2" around the garage will be damaged and collect dirt, water, etc. A solution will be to replace the top 1/4-1/8" of the board with epoxy based caulking material - after the concrete hardens for at least 28 days (the concrete will shrink somewhat during that time). Choose caulking that is designed to harden, but have some flexibility to stretch as the concrete shrinks and expands over time. Apply the caulking carefully so that it slopes slightly up towards the wall. It will create a strong, flexible protection to the board. A good way to create the needed gap on top of the board will be to use wood or plastic inserts during concrete placing, and remove those as soon as the concrete is hard enough. If left too long the bond with concrete may make removing the inserts a problem. You may also use grease or oil as a bond breaker between the inserts and the new concrete. Make sure the inserts are not too thick. Good quality caulking material can be expensive if you need to fill a large gap around the slab. Hope that helps.