Hi
What would one advise for doing internal window bucks in terms of sizing.  i had used them sometime ago with a knock down system i tried  and was making them as advised at the time 3 plus a little inches bigger than R/O so that they would be double bucked with 2 by and windows installed.  This seemed a little point less as the idea was to eliminate the thermal break  with the internal buck yet i still had to use a 2 by to install windows thus albeit a small amount once again had a thermal break.  So when switching back to preformed went back to exterior full width buck.  However I have seen that people are using internal bucks with preformed blocks now and i actually think interms of labour and reinforcement that the internal buck is the only good thing i got from the other system.
SO my question is how can I use an internal buck but still minimize the extra bucking for window install.   for one it minimizes the break a bit but 2 it also minimizes cost of having to pay for double the lumber.  Also does anyone rely soley on the windlocks to hold windowand if so what is spacing.
Thanks

Check out this thread.

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

It's a response to virtually the same question showing what I did. Not the only way, for sure, but it worked for me.

Sorry I don't have it as link to take you there directly. Learning all the steps to edit the HTML to make it that way just isn't a high priority for me!!! The webmaster should have the forum editing s/w do it automatically!

If you do a search on 'window bucks' you'll find several discussions about thermal efficiency and window installations. You might find them informative.

Here is my two cents worth:
Use v-buck. There are so many advantages to it, I recommend it to anyone.

a. Faster
b. Doesn't warp over time
c. Hang windows, doors, trim, drywall, etc. right to it
d. Clean finish
e. Automatically secures to the concrete
f. Somewhat of a thermal break
g. Price competitive - especially if double framing

If you still want to use wood, there are three ways I have seen done.
1. Span the whole form outside to outside.
2. Center of the form - double framed buck.
3. Flush with the inside, butted against foam on the outside. (Basically cutting the inside foam three inches wider and taller on the inside and slipping the wood into the hole until it hits the outside foam).

I hope this helps you.

PM'ed you

Damian

The inside dimensions of the window bucks were the same as the rough opening specified by Andersen for their windows, usually taken to the closest 1/4 or 1/2 inch. Generally, the RO was about 3/4 to 1" wider and, IIRC, about 1"+ taller, than the frame of the window. The idea was to have just enough space to get the windows plumb, and have nearby windows line up vertically. If the windows were several feet apart I didn't get carried away getting them aligned vertically. I did end up with some ROs that were a little higher than they should have been. Twisted and crooked 2xs contributed. I located the ROs vertically by measuring from the floor, not by referencing to the courses of the blocks.

We discovered fairly quickly that, even though Andersen makes high quality windows, most of the windows were not perfectly square. That meant that one side of the frame would be off plumb or off level by maybe 1/16" or 1/8". You just have to square up the window the best you can and figure out where to put the misalignment so it will be the least visually apparent.

A good axiom to keep in mind when it comes to shooting for cosmetic perfection in construction. "A fool will never see the mistake, and a wise man will know better than to say anything!"

If I had to do it over again I would take a second harder look at V-buck, but that doesn't mean I would choose it for sure. When I did my windows, as best as I can remember, V-buck was sufficiently more costly I decided I could expend a lot of my time, and afford to pay for my helper's time, to use the cheaper wood. Another reason I wasn't enamored with it was its lack of stiffness. I watched the concrete placement in an ICF house my ICF supplier was building in Hailey, ID in order to learn as much as I could about what I was getting into. He used V-buck. In several windows, even with cross bracing, the pressure of the concrete bowed the V-buck, or caused it to twist around the end of the cross brace. I'm sure this could have been avoided by more prudent practices, but nevertheless it gave me pause about using V-buck.