My new basement wall has a bunch of windows and bucks and I'm trying to determine if I need to mount the windows in the bucks, or make the bucks in a particular way to accommodate parging the outside of the wall.

Will 3/4" ply bucks with 2x8 inside the core be sufficient? Should the windows have nail flanges? Will those flanges be covered by parge? How do I wrap flashing? How do I install drip-edge?

I know how to install windows in a typical framed house, but for some reason I think everything might be different for parge finish and ICF walls. Advice please!

I believe you had a ICF distributor on site helping you with your build, what is his advice, what details are available from his manufacturer?

Which parge material are you planning to use?

If it is acrylic parge coat for EIFS, Durock's B2000 will stick to most anything, including the window frame and glass, so don't slop and leave it to clean it later. If you can recess your window back the thickness of the ICF foam, the parge coat can crack in weather (temperature) changes on different substrates, so if you set it back you can have all foam right to the edge of the window. Careful detailing of the parge coat above the window if recessed can negate the need for a drip edge if the window is set back in the wall.

You guessed it, B2000. Great to hear that it will stick to stuff, including window nailing flange/fin.

I have not asked my rep. I'm using Arxx blocks and the installation manual and video don't say nuthin about this matter. I will ask my rep but I want to hear opinions before making my decision. His way might not be my way.

So by "set back in the wall" I suppose you mean using, say 10" wide bucks in the 12 1/2" wall, so the window's nailing flange is 2 1/2" recessed from the outside face of the ICFs. But wouldn't the cracking be eliminated even if flush with the front face of the ICFs? The parge would be on ICF and the plastic of the nailing flange only.

Can I use fortiflash-type window flashing to wrap the PT before setting the window (like I'd do in a typical wood framed install)? Will the fortiflash stick to the ICFs and will the B2000 stick to the fortiflash?

Thanks for the reply.

And Chris, I assume that when you say the B2000 sticks to anything, it will stick to the peel-and-stick membrane? If so, I'll lap the B2000 over the top of the membrane, and use the membrane as window flashing since I've read that Forti-Flash/Grace Vycor doesn't stick to EPS.

It will stick to the manufacturers peel and stick for below grade (which can be cut and used as window flashing) as well I know it will stick to BlueSkin brand product...but do not exceed 2" of coverage, again it can crack and chip with temperature fluctuations

here in florida we set the windows back into the opening, attached with tap-cons directly into the concrete core, as per the window manufacturers spec's. this is a method required in the code, for masonry walls here in south florida, because the surface of the hurricane shutters has to be a certain distance away from the surface of the glazing. but it should work most other places, may need a different window flange, or a trimmed fin, if the manufaturer allows for side of frame attachment.

this offers many advantages i think:

1. gives the window/door exterior a nice reveal look, and narrows the sill on the inside.
2. lets you return the stucco around the corner into the window flange and needs only a good bead of caulk (and paint) for water proofing.
3. allows for a sloped concrete stucco sill with drip edge (we have pre-cast sills with a water dam available here).
4. allows for a wood 1x or 2x to act as a window back stop and drywall attachment furring strip, flush with inside corner. 
5. allows for impact glazed windows (heavy) to be attached directly to the concrete.
6. in the case of siding (we use mostly fiber cement type down here) you can stucco and waterproof the corners of the opening  
    (point 2. above) without the need for peel and stick tape.
7. if any banding or stone decor is needed around the opening its all attached to/with stucco or concrete if the icf has been cut back.
7. the sill gives my cats a place to sleep in the afternoon sun.

i used this on my own house re-build after the hurricanes, as i replaced all the windows on the old cmu house with impact type and then also used it on the icf addition which was built with an 11" o/o form. there i simply tap-con screwed a pt 1x6 flush with the inside of the icf's of all openings, caulked the edge and installed the window and door flanges flush against it. then i stucco'd and caulked the opening corners, regardsless of stucco or hardy on the particular wall. several hurricanes and driving rains later no leaks. just had to seal/re-caulk some screw heads on the inside of the window frames that i missed, which leaked under air/water pressure.


cmu opening with stucco, notice the window rain drains above the sill



icf opening with hardie and stucco return



hardie walls with stucco'd openings and corners from adjacent stucco walls




anyone needing more info email me.

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