Concrete Rebar

Do a googlesearch for "rebar chairs" and "rebar ties". However, because you have to ask, you should not DIY without expert, on the spot, guidance, especially if you want to place walls and beams above the foundation.

foundation concrete normally require compacted earth or a raft slab underneath, then waterproofing layer laid on top depending on the nature of the foundation (just footing or basement, etc.) then re-bars are laid on either the compacted dirt, the raft slab, or waterproofing membrane (care must be taken not to poke holes in it). of course the metal doesn't just lay right on top of the underlying material, often concrete pedestals or plastic pedestals are used, concrete pedestals should be made of the same material as footing or basement slab and should be tested to have equal strength as surrounding material. normally 3" concrete cover on all sides of re-bar is required. Consult a structural engineer and a contractor, practices may vary in different locations, but generally after you've laid top and bottom rebars, tied it together with steel wire, you pour concrete over it and you're done.

It is also possible, but not recommended practice, to float the reinforcement. You need to be working with a stiff mix of concrete. In concept, you place the concrete in the form to the level the reinforcement should be placed at. Then place the reinforcement, then place the remainder of the concrete. Like I said, not recommended, but it is done, and sometimes with good results. Based on cores I have extracted from concrete, I would say this method is successful about 40 percent of the time (my opinion only).

Another option is to place the reinforcement on the ground. Then place the concrete. Using a hook on a bar, grab the reinforcement and pull it up to the intended position within the concrete section. Definitely not recommended. Based on cores I have extracted from concrete, I have yet to find a successful installation of reinforcement using this method. It is used a lot by contractors for welded wire fabric. I just shake my head in disgust when I see it.

Chairs, supports, and hangars remain the best option, but they are not perfect. It takes experience, some skill, and care.

See Ed's picture above. But remember that is only half the problem. The other half is to keep the reinforcement where it is at while adding, working with, and finishing the concrete.