Beginning my project in Northern NM. In the mountains and typically a high radon area. Will install sub slab collection prior to pouring the floor. But is it necessary to remove the foam on the ICF prior to the floor pour in order to be able to get a concrete-concrete joint that can be sealed with urethane or other sealant, or is a concrete-EPS joint sufficient to seal with a sealer?

The seal to the EPS would probably be ok, but there is a small gap at every block joint that you will also have to try and seal. This might be as simple as pushing a foam gun nozzle all the way in to the concrete and placing a bead of foam at or below the top level of the concrete floor to join the wall concrete with your other floor edge sealant... You could also probably shoot a continuous bead of sealant along the bottom edge of all the blocks before the floor pour...

You are going to have plastic sheet under the slab. Consider extending it from under the slab and then up the wall to grade level. Tape (plus acoustic caulk?) it to the wall there. Now any gap between the slab and the wall doesn't matter. Plus you are also depressurizing the wall (which seems like it could also be a source of radon). Plus such a design is beneficial if any water ever leaks through the wall (it will get directed to below the slab).

Thanks for both replies. I like the idea of lapping up the plastic, but I'll pay attention to sealing the vertical block joints as well.

I forgot to say getting to grade level is 26 feet and another full story above the finished garage floor. Building into a hill. So I'll bring the poly up maybe a half block and then tape it. Sound reasonable?

Who is doing the slab pour? You might want to discuss this with them. It is common to snap lines at the slab floor height as a guide to fill and float the slab to. This done on the sub floor plastic can mean the line wanders vertically as the CC flows over the plastic and into corners and such and pulls/moves the plastic during the pour...

I curious why depressurization isn't needed on deep walls (seems quite similar to a slab). No expansion joints? - it can still crack.

you are using an interior drain tile for radon collection and run that to the sump crock pit that is radon fan equipped, thats how we do it, the slab is usually set on the footer against the ICF wall, but the interior drain tile collects any water and the radon. 4" gravel, 6 ml plastic, 6"x 6" wire and 4" concrete, is a very typical basement slab detail.

I hate to be repetitious but Form a Drain is the best product for the job. If I'm building it's the only product I would depend on.

I have used Form-A-Drain as well, great product, its a bit pricey compared to regular drain tile and sometimes hard to locate a distributor, but definitely a good option, also we are assuming you would need drain tile on the exterior of the footer as well.

Lots of good comments. Thanks everyone. For snapping a chalk line, that could be done before I lap up the plastic. 6 mil should allow the line to be visible, especially in done in black chalk. The engineer at this time has simply designed the radon line as a perforated line down the center. The drain is on the exterior. We only get 10" of moisture a year here, so sumps are not used. A good point is raised about why radon collection is not done on deep walls, but that should be solved by the waterproofing, especially if peel and stick. That's a lot thicker than 6 mil. I'll discuss with the concrete guy about Form a Drain. The footers are engineered as well right now are 6 foot wide, 3 foot deep with tapered sides and a bunch of steel. The original engineer died ( yeah the project has been in the works for a while) and I'll have a new one reviewing the design

I lost. Are you building a traditional footer with an icf wall on top or a thickened edge slab with a icf wall on top?

Biil, not expensive when I combine it with my mono pour system and pour the footing, walls and slab in one pour

Smart wall,
It's a traditional footer with ICF wall on top. 36 feet of height for 3 stories.

Three sides of two stories are into the hill.

The reason I asked is the 6' x3' footers are commercial multistory stuff, not used generally in residential unless you have some soil problems.

I've been a bit puzzled by the size of the footers as well. Soils test was done and the footers were designed based off of that, and I'm afraid, the deceased engineer's vision that since I'm on the side of a hill, the whole thing could slide over time. However, level I am building on is a wide bench on the hillside and I sit at the back of that. So I think he was being overly cautious. At the hill is shaley sandstone. Now as it is a total of 4 stories, three main ICF topped by a much smaller framed 4 th floor, I may have to go by IBC instead of the IRC. That may have also contributed to the heavy design. Due to changes in plans and the death of the original engineer, I have a new engineer on the project and will be discussing it in the morning.

Even a 4 story house with 8" solid concrete walls and 1500 psf soil (very soft) shouldn't require much more than a 4' wide footing.

Jon, I hoping it works out that way. Any concrete I can save is big $.

The biggest footing for a residential project I was involved in was a 10,000sq ft 2 story with a 10'high basement on sand. The engineer specified 36"x12" footings.