I'm looking at Intus windows for my ICF build. They have upwards of a 12 week lead time. With the permanent nature of an ICF wall system, how important is having the exact windows available to measure for their openings in the wall system? How easy are ICf's to modify to fit window that are slightly off? I imagine when ordering the windows I will have exact measurements from Intus detailing the openings required. So I guess the real question is how much of an advantage to the ICF contractor to have windows present?

Good choice. I know the owner, and Intus makes a great window. A good installer should have no problem delivering the proper window opening, so ordering the windows based on the rough openings and not having the windows on site should work just fine. Now, the drawings could contain unseen errors, so as we all know, what is drawn and what is reality could be two different things. Moreover, in actual construction, sometimes modifications are made. One oversight I have seen too often, which is particular to custom home building, not ICF, is placing the window headers too low, and compromising the view. What are you planning for a window buck assembly?

Thank you for your response. I was planning on treated lumber as the bucking material. I'm not too familiar with the composite/ plastic bucking systems. In my head lumber seems simpler and strong.

Thermal envelope says it's well - what you want is the window manufacturers shop drawings which will tell the ICF installer exactly what he needs to know. Regards

Thermal envelope says it's well - what you want is the window manufacturers shop drawings which will tell the ICF installer exactly what he needs to know. Regards

Thanks!

Thats exactly what I do. I just want to be proactive to help out my ICF installer (and thus myself).

Intus makes a top quality German engineered window. As far as measurements go, the rough opening must be 1" wider and 1" taller than the actual window size you are ordering.

Let's say you are ordering a 60" wide x 60" tall window. The rough opening in the ICF must be 61" wide x 61" tall.

It's pretty straightforward. Just measure the R.O. and double check it, then triple check it.

In my case... building an ICF home, having the ACTUAL windows was no advantage at all. If you're working with a reputable company like Intus (and there are many others) you'll have a window schedule with all the RO's. You really only want to bring the windows to the job site when the crew is ready.

So, build the ICF wall (pre-pour). Check the window openings to your window schedule. Check them again, and then check them a few more times. Then have your neighbor check them. Then pour, then check the openings again.

Thats good advice!

I trusted the manufacturer (Marvin) and salesperson to deliver the windows made to their advertised RO dimensions. Everything was fine, but I sweated it a bit waiting for the windows to arrive and be sure they would fit. I did my own work, so it would have been on my dime if an opening were incorrect. I don't like having expensive windows laying around on a construction site, so I didn't order them until I was sure I'd be ready to install right away.

Ditto. I used Marvin windows also and reviewed their Architectural Design Manual (ADM) to get all of the pertinent dimensions before designing and building my ICF window bucks. Marvin, like many but not all window manufacturers, sizes their windows 1/2" smaller than the nominal size. If you want a 3'W x 6'H window (designated as 3060 for 3'0" wide x 6'0" high), the actual window frame outside dimensions (not counting nailing flange if so equipped) are 35.5" wide x 71.5" high to fit in a rough framed opening of 36" wide x 72" tall to allow 1/4" clearance all around to allow minor adjustments for plumb and square. All of my window openings were spot on within +/-1/8" using treated lumber bucks, but I built them myself and am kinda anal about things fitting correctly. The only areas that I had some issues with was the door bucks. I used Therma Tru fiberglass entry and patio doors. Their door specs are kinda generic in nature and if you have any options installed like different sills or latching hardware, the actual door frame exterior dimensions may change slightly, but this wasn't readily apparent in their literature. I ended up having to shave ~1/4" off my door header bucks to get the doors to fit. It wasn't a big deal since I had an electric planer to trim them off as necessary. My recommendation is to frame door bucks a little taller, maybe 1/2" more than listed, to allow for possible settlement during the pour and variations on door dimensions. If the gap at the top of the door is a bit too wide when you get the actual doors, you can always come back and add a filler board or piece of plywood to fill the gap which is easier than making a hole that is too small bigger.

Arkie,
You and others mention using treated lumber bucks. I have never understood the reason for treated lumber. Just because it is against concrete, doesn't mean it has to be treated if They are more than 18" from grade. Problem with treated is the shrinkage and warping it tends to have as it dries out.

I am more concerned with termites than moisture is why I used treated lumber. Plus, many of my window and door bucks are at or within 12" of grade on my walkout basement. I wrapped the backside of my bucks with plastic to keep the concrete from even touching the wood.

I think I had 1 or 2 treated boards that bowed/twisted enough to be of any concern (I replaced one and planed the high spot down on the other). This is for an ICF home with 22 window and door bucks. We have pretty good treated yellow pine in my area (older growth short leaf pine in this area). I hand picked my buck lumber at Lowes at least a month before I built my bucks and stacked it with stickers to let it air dry some before cutting and assembling.

Euro companies like the triple pane window that Intus produces recommends a 1" horizontal wider and 1" vertical taller R.O. vs the ordered window size. This results in a 1/2" space around the window frame and the rough opening. This allows for expansion issues as the house settles and temperatures change. Expandable foam and tape like SIGA are used to then close up the gap areas.

Best to just follow the manufacturers instructions.

Posted By Nashvegas on 14 May 2016 09:01 PM
Arkie,
You and others mention using treated lumber bucks. I have never understood the reason for treated lumber. Just because it is against concrete, doesn't mean it has to be treated if They are more than 18" from grade. Problem with treated is the shrinkage and warping it tends to have as it dries out.

When I was getting ready to build my ICF house I had some discussions with my Civil Engineer cousin. He recommended having a vapor barrier between the concrete and wood bucks. There is a potential for condensation in the wood/concrete interface due to differential heating and cooling rates of the concrete vs. the wood. I used sill foam for that barrier. It's either use a barrier or treated lumber. Because of shrinkage and warping like you say, I opted for untreated Douglas Fir 2 x's. But they shrank and warped also! If there ever is a next time I'd be inclined to use strand lumber.

I used treated lumber (I thought it was code?), but took the time to sticker and dry the material for a couple months. I installed galvanized lag screws from the back side, leaving the heads sticking out about 3 inches to be buried in the concrete, and secure the bucks from moving. Since i was building the house myself, the bucks were visible for a long time, and never seemed to move at all. I did my windows differently, making the RO 5-1/2" per side oversized, then building a subframe for the window so that I could create tapered window returns to reduce the tunnel effect of the thick walls. We really like the way they came out, and make the windows seem much larger. Trim and window treatments are tricky though.

Why not just have raw exposed concrete as the RO? Once the concrete is poured and cured, the wood forms can be knocked out and then just install the windows directly into the concrete with concrete anchors?

That way you don't have to deal with wood expanding, contracting, rotting, etc. Instead of THREE dissimilar materials (concrete, wood and window frames), you would only have TWO (window frames & concrete)

Why you put wood between concrete and windows?
it is insane.
it is possible to connect windows to concrete directly.
I used topcons.
Some use foam only.