OK,

I have my freshly poured ICF walls over there looking back through the window at me.
21 openings. 15 windows and 6 doors.
All are bucked with ripped PT 2x10 or 2x12.
My doors and windows were just delivered.

We wanted a partially inset window style not flush with outside nor inside.
We wanted a marble inner sill below the casement lower edge.
So the installer said to go oversize with his bucks and then do a double buck method.
His bucks were ripped to fit and glued in with timber spikes left to be gripped by the concrete.

I read the ICF learning center section.
I searched double buck and read a bunch of old threads.
I am reading posts and trying to decide what to do next....
The installer foreman said he would come after hours and do some tutoring on how to install the doors and windows.

A I have read, PT bucks are maybe lemons, how do I roll with the punches here and make the best out of this that I can for the long term performance? Liquid flashing? What wood to use for the second re-rap?

Thanks.

I have used only PT bucks with all our ICF projects, mainly because when I started, they were the only thing available. And I don't consider them to be lemons. I have looked at several other options over the years and I honestly cannot justify the additional costs, which can be huge. Any other wood you need for bucks can be standard SPF framing lumber. How you flash and finish your openings will depend on the type of exterior finish you intend to use. Flashing and waterproofing is not rocket science, just a little common sense.

We want to use stucco. From some threads here it seems we might have been better off with inner bucks or whatever they are called.
The installer didn't mention or offer us that option.

I have 12 of one window size so I will use it as discussion example to solicit assistance. 3 other windows are bigger.
I measured the current buck opening. 44 x 20.5 on ripped 2x filling the 9" block width.
Bottom part of the buck seems to be a ripped in half 2x6 with each part pulled to the edges leaving the sill open for the pour.

My casement windows have nail fins and 4-9/16 jams.
The frame dimensions are 40 x 17.
So installing double bucks 2x4 for the sides I have 17+1.5+1.5+ shims is about 20.5.
For the top and bottom I want to somehow install a marble sill on the inside.
It is 3cm, or about 1-1/4" thick.
So I think I sit the window on the marble (40+1.25+ only 41.25, 2.75" remaining) and then I have a large gap at the top to fill in?
Or I could sit it on a 2x4 on the bottom edge and somehow slip that marble sill in there behind it.

Another newbie story. We already built a small ICF house with 3 casement windows about 20 feet from this new structure.
I ordered the windows without nail fins but with jams and ended up pulling the staples off and removing all the extended jams.
I sit the window on the marble sill and basically glued it in place.
But this time I thought it might be better to have the nail fin and 4-9/16 jams.

I appreciate any advice here. I might get an onsite tutorial from the ICF installer foreman but it might not pan out...

Thanks.

Are you not going to install the secondary bucks on the top and bottom of your window openings?
Also, we normally set the marble window sills to the inside of the window itself, not with the window setting on the sill. This allows for weatherproofing the window without involving the marble sill, which is normally considered strictly a finish trim.
And while securing liteweight vinyl windows by way of the nailing fin may be OK; larger, more substantial windows should be secured using screws through the jambs into the framing bucks, to provide a more stable installation.

I agree with Wes.

If you do decide to use screws through the window jambs, then be sure to shim the window at each screw location to keep the screw from pulling the window in too much.