How frame overhang on low-slope roof?
I’m building a 16′ (out) by 27′ house addition. I’m using 2×10 rafters 16″ OC, 5/8 plywood, 3.5″ poly iso, 3.5″ PT perimeter boards, GAF Liberty stick-on rolled roofing.
What’s the best way to have an 6-12″ overhang on all sides? It wouldn’t have poly iso so just going w/ 18′ joists won’t help. If I put it under the plywood the roof will have a 3.5″ step-down and require extensive flashing – I’d like to have the overhang flush w the roof and cover w/ same roofing.
Only way I can see to do it is create a separate frame around the outside w/ lookouts & fascia and then attach to the perimeter boards 5/8 below the roof top to allow for plywood. This is a weak design though as there’s no continuity between the roof plywood and the overhang.
I could run the plywood out on top of the joists and put the lookouts on top of this. But this would waste a fair bit of plywood.
Replies
Can't you just extend the rafters, and use a dropped gable end and the "ladder" extensions (whatever they're called) on the "gables"?
(Oh, I see, you've got the polyiso on top of the rafters. Well then just add spacers/shims equal to the polyiso thickness to the rafter tails.)
A dropped gable + eave would work but the flashed corners and inside edges would invite water retention. And water flowing over and edge and out again to the gutter would spash.
I'll probably just frame a ladder from PT 2x6s and screw into the rim joists and eave. But this will be discontinuous w/ the roof plywood and thus weak - ladders work on pitched roofs because the plywood sticks out. And I screq down along the outside board.
Bolting through the rim joist would help but the 2x6 won't catch much of that due to the ripped 2x4 on top of the joist (to create the slope).
I might buy 18' joists and exten them over the eave end but this requires bloskinc between each to seal the inside and still leaves the outside of the eave 3.5" below the roof. I could run the polyiso out to the edge but that's wasting 1,5 sheets of it @ $45.sheet incl tax.
Net, there are ways to do it but none are robust or effeciently use materials.
jfh0jfh
Frame it so it stays up and is sound.
Shim up the joists around the perimeter to make up for the lack of the 45.00 foamboard.
You want it flush and sturdy, build up what you don't want to foam.
Best of luck.
Waste material.........
or waste time.
Neither is very beneficial. The end result is what's important.