We normally use a full treated buck installed with landscape spikes. The engineers will typically dictate what they want for securement. This is over kill from ring-shank or other types of nails. Most engineers won't allow installation after the pour, as they considered it part of their pre pour inspection process. Most will depend upon your region and engineering. For flashing have you considered Aqua flashing? It's a liquid applied type and can be installed over the form and the buck to create a nice tight seal before you install the window. Then come back and do the three sides and your set!

I was quoted $6.45 per linear foot for V-Buck from my contractor. That's just materials. He said rather than rip 2X8's down to 6", just use 2X6 and foam the gap. PT 2X6's run about 50 or 60 cents a foot, IIRC. Rough guesstimate- you're looking at an average of about $100 per opening for V-Buck. In the grand scheme of things, that's not all that much money, and I hear it is easy to work with. I haven't decided yet; I'm trying to shave every penny though to make ICF a reality.

Besides the cost of the V buck you still need to brace it before the pour. The v bucks typically require more bracing then a pt buck depending upon the size of the opening to keep it square. Did you consider the weight of the doors on the v buck and them swinging?

Posted By jdebree on 25 Mar 2012 04:32 PM
He said rather than rip 2X8's down to 6", just use 2X6 and foam the gap. PT 2X6's run about 50 or 60 cents a foot, IIRC.

That's what I did. Worked good. It's discussed in these threads. There're links to photos showing what I did. I went with the suggestions of walltech. If you search on his name, or mine, and window bucks, you'll find several threads from about 3 to 4 years ago.

http://www.greenbuildingtalk.com/Forums/tabid/53/aff/4/aft/63368/afv/topic/afpgj/1/Default.aspx

http://www.greenbuildingtalk.com/Forums/tabid/53/view/topic/forumid/4/postid/60495/Default.aspx

A pressure treated #2 yellow pine 2x8x16' at the local Lowes is currently $15.72. That is enough to do a 3060 window opening if you use the 1-1/4" ripped off pieces in the bottom of the buck. Add ~$1 for PT rated screws to hold it together. Then you will need some internal bracing at ~2' on center, but you will need that with any type of buck material you choose.

Using a full 6" board in the 6" ICF cavity along with 3-1/2" screws and 2" plastic EIFS washers every 8" around the perimeter makes for a strong assembly with little likelihood of failure or movement during the pour.