Window openings in ICFs

[bkrahmer]

Hi again. After talking to a few people who've done ICFs themselves, I'm also thinking of doing it myself. I have what is maybe a stupid question. I want to put several acrylic block windows here and there in the basement walls (5 of them total). I will also have one egress window. My question is this: do I need to worry about getting the concrete to flow underneath and completely fill the area underneath the window bucks? I've never worked with concrete, but it seems sufficiently thick that it wouldn't flow in there, and leave a big air bubble. Maybe there's a trick to it? The windows I'm thinking of have a rough opening of 21.75x14.25". I'm thinking of putting the top 12" from the top of the (8') wall. Is that what you would recommend? BTW, I love the concrete calculator! Very handy.

[Rich]

You'll want to wood frame a window buck. Make sure the bottom piece is not nailed. Pour up to the level of the bottom of the window. Finish it off so it looks nice - put your lower frame in and continue pouring. Easy :)
If you're that close to the top of the wall make sure you have rebar detailed to go through there with hoops .. it should look like a frame of rebar with 2" clearance. Egress windows need to be no more than 30" from finished floor.. just a point to remember.

[bkrahmer]

Thanks for the info, Rich. One clarification, though... Should the bottom piece just drop right in (the width of the bottom piece would be 21.75), or would I slide it under the other pieces after it has concrete to rest on (the width of the bottom piece would be 24.75) so the rest of the window buck can be supported by the bottom piece?
BTW, I thought the maximum sill height from the floor was 44". I was planning 36", but maybe I'll do 30". Thanks again

[Rich]

The 44" maximum could very well be true (haven't ever checked that). On the 30" you will probably have to check with your local codes.. here I'm pretty sure it's 30".. it could very well be different.
Best case scenario would be that the bottom piece would span all the way across so you don't have end grain in contact with the concrete - not a huge deal if you're using pressure treated lumber. The reason I say to put it on the inside so it can drop in is to withstand the pressure of the concrete as you pour up the sides. You should put cross pieces up the sides to withstand the pressure of the concrete also.