That could work.
It's a bit more work up front. And you have to monitor the pour a bit more carefully.

Sorry to resurrect an old thread, but I've got a VERY similar situation and would love some advice.

I've also got a walk out basement. Back walls are retaining about 6'. ICF walls are generally 9' tall in the back and 12' tall in the front.

My engineer has given me the option to either do 3 pours: (footers, walls, then slab), or 2 pours, but in my case the first pour would be footers and slab in a mono-slab situation (note, NOT a mono-pour where you do the footers and wall at the same time). Then you form up the ICF and do a pour of the walls. I am not experienced enough to know the pros and cons of this method. Off the top of my head I can think of a few:
1. PRO: one less pour. One less concrete crew to hire. Things come together quicker.
2. PRO: I've got a nice level slab to work on when stacking blocks and setting my bracing.
3. CON: I'm blasting into my nice new slab when securing my bracing.
4. CON: There's a thermal break between the slab and the walls in the 3 pour setup. (my engineer seems to believe this is totally irrelevant in southern AZ when you're well below grade, but still....)
5. CON: It's going to be harder to smooth out my slab when it's ringed by 4' high #4 rebar spaced every 16". (not sure about this one because I think it'll be just as hard if not harder to smooth things out when that rebar is replaced by walls in the 3 pour example)
6. CON: A smooth slab/footing is perhaps not the best surface for the concrete in the ICF to "bite" into. The rough surface of a separate footer probably secures the wall to the footer better (maybe???)

Just some thoughts. Again, I really don't know the answer here. Looking for some advise from those who have dealt with this sort of thing before.

How your GC prefers to do it is usually the best way...

Many ICF GCs like to pour footings and walls in one pour. Many like to pour footings and slab in one pour. These days we do a lot of stamped hydronic radiant heated floors and we like having a level/flat footing to place ICF and use interior bracing. So we like to pour footings first, then ICF walls, and then the slab which can involve many more seperate floor pours when we are stamping them. So how you will finish your floor is an important consideration too.

You can also brace your ICF walls from the exterior side if you know what you are doing.

Thanks. In this situation I"M the GC (ha ha). We will likely hire a concrete crew to come and manage the pour, but we are likely going to be stacking the blocks, setting the forms, bending the rebar, etc. If a mono-slab can work, I'd prefer to save the cost of having the crew come out one additional time. The lower floor is a workshop so it's likely to end up with epoxy over concrete. No radiant system in there.

Another issue I've found when reading around is that in a monoslab the slab is integrally connected to the footers. The load on the footers is significantly greater than that on the slab, so it'll likely settle differently. For a simple frame single story, this is likely not an issue, but for a 2 story structure with ICF blocks making up the 1st floor, we're talking about a LOT of weight. When the footer settles differently than the slab, you end up with cracks along the walls. Again, I don't know if this is really a "real issue" or not, but it's one of the concerns I've read about.

This is where soil prep becomes important. Proper sub-slab makeup and compaction is Not Optional.

Also, monolithic slabs tend to be thicker than slabs with separate footers. Precisely for the reason noted.

It’s not so much the settling that causes the problems, it’s differential settling that causes the problems.

Where we build, we often run into expansive soils and boulders, the perfect mix that will cause differential settling. So this is one reason why we prefer to start with an engineered pad that considers the soil conditions. If you just dig a trench and you don’t know for sure that the soil is uniform a foot or so below the entire trench, you may be at risk of differential settling. The other reason we like engineered pads is that we like our buildings to be elevated slightly above the local terrain for aesthetics and drainage and we don’t like crawl spaces.

We also like to float our slabs within the ICF walls on self-compacting pea gravel. This allow the slab to move independently from the footing and ICF walls in a seismic event. Large inflexible concrete structures don’t often fare well in seismic events.

OK, Revisiting this topic! Option 4- Attached picture (Hopefully it posts). 1.Form the footings using fastfoot, attached to 1 or 2 courses of block. Use the Zonts and Zuckles that I've got on either side of the blocks to straighten, plumb and level everything up 100%. 2.First pour up to just the bottom edge of the first block, footing and first courses are now dead on. Minimal form stripping required. 3.After that just stack and brace blocks as normal and pour the walls all the way up. 4.Finally, pour the floor at a later date. What do you guys think?

You will have a cold joint in your basement wall which is not normally allowed and certainly not desirable. Not sure why you feel the need to deviate from conventional ICF construction methods? If it is to save a few dollars, maybe you should just wait until you have adequate funds and do things properly.

I dont think it will save any money, probably would save some time though.

Is that considered having a cold joint in the wall if the first pour ends at the top of the footing and not into the first block as the drawing shows?

Would there be much of a difference in the strength and location of the cold joint in the previous picture vs this one? (blue line)

Been selling a mono pour system since 2004. It uses regular footing form and allows you to pour the footing wall and floor in one pour.

Let me know what that entails, I'm definitely interested.

I can’t quantify the strength of the various options, but intentionally creating cold joints in walls, especially basement walls is not advised and normally not allowed unless mitigated by having additional rebar. However, the rebar doesn’t mitigate having water intrusion at this location.

Your photos show the blue line cold joint at the wall/footing interface and NOT two ICF block courses up as you described. Did I misunderstand what you described? Having a cold joint at the footing/wall interface is commonly done and not an issue. Just make sure your finished basement floor is well above this interface. We typically create a 1.5" D x 3.5" W channel in the top center surface of the footing by placing a 2x4 in the footing form before pouring it. This 2x4 is then removed to create the channel before stacking the ICF blocks and pouring the wall which results in a stronger and more water tight footing/wall interface. We also do 12” OC dowels and 12" OC vertical wall rebar.

I have learned much about ICF construction from Smartwall over the years of participating on this forum and I think his mono pour system would be the best approach overall if one had the confidence and skill to successfully accomplish it.

Yes, the first pour would come up to the bottom edge of the first form only, and the finished slab would be well above that. The only reason to install two courses before pouring the footing would be to assist with leveling and fine tuning wall locations.

The benefits of this (in my opinion) is that instead of spending time forming the footings, stripping the footings then getting block locations perfect, I can just spend my time getting my fastfoot & 2 courses perfect.

And yes, Smartwall definitely knows his stuff! I plan on using some of his techniques in my build. I dont think I would be confident enough to pour footing, wall and floor in one shot though

I would recommend using the Fast Foot system. It's different from mine but will do the job. Where I am in upstate NY we have quite of bit of radon, so my customers use Form-A-Drain. By using this product it allows the floor to be poured at the same time. Zonts and Zuckles are a great product. I'm slowly replacing my steel bracing with them.