I have a customer that wants to pour a removeable form foundation and set Lite-Deck spanning 20' on it. Do we need to pour the top two feet of the wall with the floor system? That is how we have always done it. Or can the foundation be poured to the bottom of the floor system, with rebar sticking out to be bent into the floor?

To be safe and wise, I think this is really a question for a licensed structural engineer...and not an Internet discussion/solution. Both approaches could likely be successfully accomplished if done properly. You would first want to bend the rebar to its final final position BEFORE pouring any concrete. And you don't want to create any cold concrete joints in locations that would compromise the structural integrity of the floor or walls given the loads they will experience.

An engineer would be recommended, but they rightfully want to make the decision of whether or not to use an ICF floor system, before incurring the expense of an engineer.

Well, as you well know, there are pros, cons and tradeoffs that are made when doing construction. We have not personally used Lite-Deck, but we have read about it and we have designed hydronic radiant floor systems for clients who have used Lite-Deck successfully. Seems like a good system...but there are several other good systems too... Maybe Smartwall or someone else with more actual experience with this specific floor system can provide better guidance.

Gayle

Sorry I've never used it. Never fit into my plans. Truss joist and Burmon hangers are my thing.

We very rarely pour an ICF floor anymore, to time consuming. We instead use iSpan Total Joists and install a new Sulfate Magnesium Oxide subfloor panel on it. we use Steel Ledger boards and Burmon Ledger pins Embedded in the ICF wall to bolt the Ledger boards to. We build the floors in cassettes ( 12' wide sections by Up to 30' long). we install a Sulfate Magnesium Oxide Drywall panel on the bottom of the cassettes and install a Radiant heating AND Radiant Cooling panel ( the panels do both radiant Heating and cooling and they install just above the ceiling drywall. We pre wire and pre plumb the cassettes and install a sulfate Magnesium Oxide 20 mm subfloor panel on the top of the cassettes. The cassettes are built at our shop and loaded on a trailer and shipped to the jobsite JIT. The iSpan floors can span up to 30 feet clear span.) We also pre panelize our ICF walls and our internal steel stud framed walls at our shop too. We pre wire and pre plumb both and install the sulfate MgO drywall panels on the interior of the ICF walls. We install the windows and door bucks and reuseable buck braces in those walls and install MST Bar for vertical Concrete reinforcement and horizontal reinforcement in corners and over Lintels. All the rest of the concrete reinforcement is done with Helix 5-25 micro rebar (added to the concrete at the concrete plant. We are working on the engineering now to start building custom "drop in" Kitchens and bathrooms. They will be completely finished at our shop including everything you see in a Kitchen or bathroom and are loaded on a trailer and shipped to the Job site for erection. We use SIP roofs and the outside and inside sheathing is all sulfate MgO. The SIPs have internal steel beams that run up the sips and have EPS foam for insulation (R-60) and have a rated wind load of 230 mph. The SIP panels come 8' wide by up to 24' long But I suspect longer ones are on the way. We can basically build a house (5,000 sq ft) in 5-10 days depending on weather. The only thing left to do in the house is trim, hang the doors inside install door hardware, Install Light fixtures, Finished Floors and Paint. The whole process takes 3 weeks...the Radiant system requires no duct work and is installed in the ceiling. it is Not a tube system the panels are mfgred by Therma-Hexx. If the house should spring a water leak in the house or the house get flooded you don't even need to remove the subfloor or the dry wall (sulfate MgO is water resistant, and mold and mildew resistant. has a great fire rating -no paper on the drywall. has good sound proofing qualities, and is High impact resistant. ( don't recommend you kick or hit these walls when you loose your temper you will definitely be making a trip to the hospital! The Sip roofs do not require Rafters or trusses! And we use a SIP wall panel made of the same material if we need to build roof dormers. We use a combination of Fast Foot bags and Form-a-Drain for the footers and Install Fast Foot Mono pour Legs on the bottoms of our ICF walls and we shorten the inside wall by 6" (to add 2" of GEO Foam under the 4' concrete floor. We have special braces ( not your run of the mill ICF braces that brace the wall that allows us to pour the footer, the walls, and the basement floor or slab in one mono pour.

If the client insists on a concrete floor then we install the iSpan Composite total joist system that you install a steel lewis deck on the top of the steel total joists and pour 3 inch of concrete. (no shoring required!) Once you start using sulfate MgO panels you will never need another concrete floor again! (except of course your concrete basement floor or first floor slab.)

I don't have an answer.
A lot of what I'm seeing is spray foam underlayment (2") before the slab pour, If more is required, they use foam sheet.
Talk to your architect and your ICF contractor.