Inset 2×6 sill plate
harp2424
| Posted in Green Building Techniques on
We’re in the final phases of house plans for our new build in Illinois(5A). I’m very interested in adding 2″ of XPS foam, but not so excited about it extending beyond our basement foundation wall. Would it be acceptable to inset a 2×6 treated sill so that the foam does not extend beyond the 8″ basement foundation wall?
I’ve attached a drawing to help explain…
Thanks a bunch – I really appreciate all the advice I’ve learned on this site!
Craig
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Replies
Craig, In general the only thing that limits how far the sill plate can be moved in is maintaining bearing for the floor joists. The reason for installing foam beyond the foundation is usually either that a) the design calls for the foam to extend down over the foundation exterior or b) the wall is too thick to have all its component parts bear on an 8" foundation. Your detail works fine.
Craig,
Have you considered extending the insulation down the exterior of the basement wall?
Are you in termite country?
Thanks Malcolm - good to hear that I'm on the right track.
Lucas, I did consider foam to the foundation footings, but we're not thrilled with the options to cover the exposed foam. We'd prefer some sort of stone/cultured stone, but being advised not to do that over foam. Yes, we do have termites....
We're supposed to get back to our architect this week, so this key detail will determine our foundation plan. Any other variations of this wall assembly that I might not be thinking of?
Thanks!
Craig
Craig,
Like Malcolm, I think your detail is probably fine as long as it can dry to the inside...
Stick with open cell foam if you intend to spray the inside of the rim board and no poly on the interior side of the stud walls.
If you haven't already, consider taping the exterior sheathing as an air barrier.