I'm looking at building a 2900 sq ft ICF house. The garage will be attached with a mudroom between the house and garage. In order to ease the construction for challenges and timing, I'm considering building the house and then pouring the garage stemwall later. The garage will be stick built, so it will just be a 4' stem wall attached to basement wall in 2 spots. Would you use a T block and stub it out a bit and cap the end off? Or should I just try to bend some rebar at 90 degree's and stick it through the foam where the walls will be and sheet over the spots with plywood.

I just used hooked rebar to connect my ICF wall to the adjacent garage slab. I took ~3' long pieces of 1/2" rebar and put a 6" bend on one end, then poked the straight section of rebar through the foam so that ~24" of straight rebar protruded into the garage slab. I wire tied the hooked rebar to horizontal rebar in the ICF wall to hold it in place. Since I only had a 1/2" hole poked through the foam with rebar filling the hole, no plywood scab was needed. Note that my ICF was LiteForm foam planks and ties, so I could poke the straight piece of rebar through the foam before assembling the block. If you are using a pre-made ICF block, you may need a larger hole than the size of the rebar and a plywood scab over the hole may be appropriate.

My garage foundation walls are filled concrete block with an "L" block at the top course resting on a poured footer. The downslope side of my garage foundation wall is over 6' tall, so I wanted it well secured to the ICF wall. In the ICF wall where it meets the garage block foundation wall, I cut 4" round holes in the ICF at 16" on-center vertically to align with the center of the intersecting block courses. I inserted long "J" bolt anchors into the center of these holes using scabs of plywood screwed to the ICF with nuts on the J bolt on each side of the plywood to hold the anchor bolt in place. After the ICF pour was complete, the plywood scabs were removed and there was a 4" diameter concrete abutment flush with the face of the ICF with ~3" of anchor bolt exposed. I then took the anchor bolt nuts and welded 2 heavy 3/4" ID washers to opposite flats on the nuts. I then threaded the nuts onto the end of the anchor bolts and aligned the washers horizontally at ~4" from the face of the ICF and made sure that the washers aligned vertically so that I could drop a 1/2" piece of rebar down through the washers from above. When the garage foundation blocks were placed, the block layer used a hammer to knock a hole in the ends of the blocks where they intersected one of my anchor bolts. After the blocks were placed, we dropped the 1/2" rebar down through the welded washers from above. This vertical rebar centered roughly in the block core adjacent to the ICF wall. The blocks were then filled with concrete when we poured the garage slab. This provided a strong tie from the garage foundation walls to the ICF basement walls. I did it this way to make it easy for the block layer, rather than have to deal with 2' pieces of rebar sticking out of the ICF wall. But if your garage foundation is poured concrete, I see no reason to go beyond just tying it to the ICF wall with hooked rebar poked through the foam and extending ~2' into the poured wall.

Go with a no. 5 rebar for the tie in stubs. One important consideration is to extend the footing form past the break for the wall. As with any wall section you don't want them to end at the same point

Posted By smartwall on 26 Dec 2018 01:13 AM
One important consideration is to extend the footing form past the break for the wall.

Any suggestion on how to do that? There will be a 4' change in elevation of the footings where the garage meets the basement.

Take concrete blocks and stack them to your required height install rebar, form and pour. That's one way to do it. Sounds like you may need help from a pro in your area.

I did like described above for my basement to garage transition. I extended the footings out past the ICF wall footing about 2' or so with a couple pieces of rebar sticking up ~2'. Then I had concrete block columns 2' x 2' built up to the level of my garage footing. I used blue tapcon screws to attach form boards to the sides of the block columns. I also drilled horizontal holes in the top blocks to extend 2 pieces of 3/4" rebar from the block columns across the over dig area and several feet into the garage footings on undisturbed soil just to provide a little extra support over that area that I had back filled with gravel. When we poured the garage footing, we completely filled the concrete block column adjacent to the ICF wall.