I live in Iowa, and I have an ICF walkout basement and my windows were designed so that the window buck is larger than the window, and there is a second frame within the window buck frame for the actual window like in the diagram I attached.

I've been trying to figure out the best way to flash this opening, and if the products I have will work. My windows require that the flashing be a non-asphalt based, which I think is also what the ICF foam requires (A-one form.) There is a 1" layer of DOW blueboard as you can see.

I have Tyvek flexwrap for the sill flashing, and straight flash for the jambs and top flashing.

Would this work, in this order? (see picture):

1. Straight flash the bottom joint of window buck/ICF
2. Straight flash the side joints of window buck/ICF
3. Cut slit in ICF foam and reglet Straight flash into foam at the top joint of window buck/ICF. (Use tape over flashing)
4. Install backdam (i plan on using foam weatherstripping)
5. Apply flexwrap to bottom sill in R.O.
6. Apply straight flash to jamb R.O. and over backdam.
7. Apply caulking to sides and top of R.O. approx. 3/4 in. away from R.O.
8. Install flanged window
9. Apply straight flash to jambs over side flanges on window
10. (windows have integrated drip cap) Cut slit in DOW foam, Apply straight flash to head covering head flange, regletting into foam. Tape over head flashing.

Am I missing something here? Is there something I shouldn't be doing? Your comments will be greatly appreciated.

Thanks.

Nice drawings....are the window flanges flush with the buck and thus the outside ICF wall?

The window bucks were recessed in 1" so when we installed the DOW blue board it was flush with the ICF foam. So the flanges on the window will be on top of the blue board.

Thanks for the praise, too. I did those with the software Paint.

From what I can see the drainage plane makes sense....you flashed the top. I would also consider applying foam safe peel-stick tape in a shingle type method from below to seal everything up.  Also please share the reason why the original window buck was recessed?  Insulation?

So are Tyvek flexwrap and the tyvek straight flash not foam safe? It is a butyl based product, not asphalt based. What do you mean by using peel and stick tape in shingle fashion from below? From below the window? To where? I put the straight flash (green in the picture) on the bottom joint between the window buck and the ICF opening, then use the flexwrap to create a sill pan, which goes over that bottom piece of flashing. Or do you mean on the sides of the windows all the way up? That'd be a lot of tape and kindof expensive. What I could to is cover around the windows with Tyvek, over the flashing on the joints of the buck/ICF. Then flash around the tyvek, and reglet the top flash over the tyvek.

Yes, I recessed the buck 1" and covered it with dow foam to minimize the thermal break of the studs. The way the windows were designed was so that on the inside we can slope the drywall from the sides and top towards the window, to minimize the tunnel effect, since the walls are so thick. That cavity around the window will be filled with foam insulation, and if I can manage it, I'd like to use air krete.

Thanks for the response.