Window buck depth
Hi. I have a question about installing windows on walls with rigid foam over the wall sheathing. I’ve read several different ways of installing them but seems like a lot of conflicting answers. Should my window bucks be installed before the foam to the depth where the flanges will be flush with the foam sheathing that is on top of my wrb and plywood/osb and then have my battens running over the flange for trim or should the depth come out 3/4” more to end up flush with the 1x material I plan to install over the foam as rain screen battens. My plan was to have rough opening framed out 1 1/2” wider in all dimensions and have rigid foam cut to the same dimensions as the sheathing and then use 1x lumber on the inside of the rough opening and come out flush with the foam and then picture frame with the same 1x material around the opening and over the inside 1x material. This would bring my assembly where the window sits even with the rain screen battens. Thank you for any response.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
I typically run the 2x window buck to the same plane as the outermost edge of the firring to strapping. There's a couple reasons I do this, I make the wall sheathing the water and air control layers, it is easier to connect the 2x to those control layers than trying to connect the 2x plus the added 1x firring board. This also allows me to leave a small space between the firring and window buck for a drainage space.
I really like the detail that Rachel Wagner and Leah Karmaker use in their wall assemblies with CEI. Similar concept, except they use a nailbase panel rather than rigid foam or mineral wool with firring strips. https://www.greenbuildingadvisor.com/article/installing-windows-over-nailbase-panels
Hope this helps,
Randy
I don't like to do origami flashing around window bucks, so I keep the window buck at the rigid/wrb plane.
To make the window removable later, you want to stop the rain screen just before the window flange. You can use winder trim that sits on the rain screen or tack a couple of pieces of plywood over the flange as a nailing surface for the window trim.