Best way to install windows in ICF?
Hello,
I am trying to build a small out building. Guest House? Shop? I am not sure yet.
It is being buit out of ICF (insulated concrete forms). A specific type that is made of portland cement and recycled styrofoam which results in a screen-grid type ICF.
Thickness is 10 inches before stucco exterior and plaster interior.
I have 3 jeld-wen casement windows. I did not get the nail fin since this is not normal wood frame construction. I got the wide jams. Like 6-5/8 inch wide.
The windows came with instructions but aimed at typical wood frame and talking about folding back the house wrap. etc.
At the window rough openings I think I have 2 options.
A. Make wood bucks that will stay there to be the trimmer studs, sill and header.
B. Or as I would prefer, I can create smooth concrete surfaces on the sill and sides, with maybe a large wooden lintel. Like a stone built house.
My question: What is the best way to install windows in this situation?
Thanks
Replies
Texas fire
You have to build wooden bucks,, no other way to pour cement and not have it leak out.. remember when building those wooden bucks to drill large round access holes in the bottom so you can pour concrete under the window during the fill.. Make sure the holes are big enough to let the concrete chute in and large enough to fill the whole area under the window..
You will also want to make those bucks out of a decay resistant wood.. pressure treated or white oak.. I would still go ahead and wrap those timbers in poly as an extra precaution against decay. Remember to put lag bots into the wood going into the concrete.. I've seen wooden bucks shrink and come loose. The lag bolts capture the wooden buck and won't let it shrink away. Tall or wide windows will need extra bracing across them to keep them from collasping under the pressure and weight of all the cement
all I can say is what I do.
I make a PT window buck in the ICF wall. use either a dado, a legdger strip or several SS screws in the backside to anchor it in the crete as we pour that. The inside dims of th ebuck match the RO for the window.
Then I use windows with nailing flange and install as in a framed wall within the buck, using vycor or Tyvek tape to seal the fins to the foam, with the tape under the bottom fin and over the others. Then we stucco the exterior
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If I am reading correctly you want to recess your windows on the exterior and return the stucco to them, sort of like an adobe house. I did this on my own home. From the inside the windows are not set into such a deep recess. You still need wooden bucks. I made a two piece buck so that I could remove the outer piece after the pour and leave in the treated piece that was the depth of the window, which creates a step for the window flange to attach. It would have been easier to have bought windows with the flange.
John