Overframing a Roof for Large Overhangs
I’ve written in before regarding our upcoming house in California’s high desert. We’ve headed into structural and I’m finding I’m having a heck of a time laying out the roof. Without getting overly granular, we’re just trying to frame a 25×65 foot box (with one 3ft bump-out on one end) with 4′ overhangs. I’d like to apply a layer of external insulation, furring strips and a standing seam roof over the whole thing.
I was thinking the house would be a great candidate for “overframing” the roof…meaning we could end the TJI joists at the walls, the roof and wall sheathing would meet at a taped seam and a second set of roof members could be affixed through the sheathing. I found examples of this in Passive House Details by Corner, Fillinger and Kwok. And sent the engineers scans of those and screen grabs from Matt Risinger’s videos on framing his own roof in Texas.
The structural engineers weren’t crazy about the idea, principally because they didn’t know an effective way to affix the rafter tails to TJI’s below. I know Matt Risinger just dropped in long (expensive) screws through the rafter tails..but is there enough meat in a TJI to make this viable? What is the SOP for this…and on a house this size am I asking too much with a 3 or 4 foot overhang?
Finally, in your expert opinions, would conventional framing and metal supports to bolster the corners be a way to address these problems? I see endless examples of fairly deep overhangs being framed with what seems to be 2×4 and 2×6 dimensional lumber in the area. What are they getting that I’m not. Can someone help me out with this? What am I missing?
here’s a detail from the book, Passive House Details. Also, we’re in climate zone 3b, but at 4500 ft, we have a snow load of 30 psf and temps in the 20s in the winter. So I might cheat us toward Mixed/Dry.
Thanks so much for your help…
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