I have a question about order of operations for my digging and formwork. I'm building a 15' x 23' detached MIL unit in my back yard. I've decided to use a reinforced monolithic slab. There will be a foundation drain around the perimeter of the slab, made of perforated pipe buried in gravel and enclosed in fabric, which will drain to the side sewer. Lastly, there will be rigid foam insulation under the slab, as well as vertically along the exterior edge of the slab (including the above-grade portion, which will be 6"). The thickened edge of the slab will extend 18" below grade. I'm still waiting for my final drawings from the engineer but it will basically be this: [ATTACH]61152[/ATTACH] So, how do I go about actually digging the trench for the thickened edge? It seems I have two options: [LIST=1] [*]dig a 14" wide trench, line the outsidewith a 2 ft. wall of vertical insulation, and build 6" high forms for the above-grade portion, [I]then[/I] after the concrete has set, dig another trench and lay the drain; OR [*]dig a trench that's 3+ ft. wide that will contain both the footing [I]and [/I]the drain, which means I need to build 2" high forms inside the trench that will need to hold back a whole lot more concrete. Then I can remove the forms, lay my drain, and backfill everything. [/LIST] Are these both valid approaches? Is one clearly better?

I want to make a concrete garden bench seat, about 20 by 48 inches using a 2x4 form. Can anyone offer me tips on how to layout rebar for it?