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Shed roof construction questions

3K views 3 replies 4 participants last post by  95025 
#1 ·
My Dad and I want to build a shed roof off his garage.
I plan to bolt a ledger on the building right underneath the rafter tails overhang and attach the rafters to this, then maybe flash the space between the existing roof drip edge and the new roof.

With the dimensions that he wants (10' 4" rafter span) and 6'6" of headroom under the header at the low end, I've calculated the pitch would be appx. 1 7/16".

Question 1: Is this is a problem? Can this tolerate a metal roof?
If so, what is the best way to frame this? Can I do 2X8 rafters 2' OC with horizontal 2X4 purlins every X inches, then metal right on that? Or would it need to be sheathed? If it needs to be sheathed, we would probably do some sort of "rolled" roofing.

If the pitch is a problem, the only alternatives are to either hang the roof right off the rafter tails (I don't like this structurally or visually), or build the roof right on top of the existing roof, and lap whatever material under the asphalt shingles. I don't like this either.

Thanks.
 
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#3 ·
torch on roofing can also be used.

in regards to flashing the space between the lower shed roof and the garage roof. most definitely. having one roof start directly below another needs to be treated as a single roof by having the joint sealed.. with the shed roof being such a low slow any sitting water can blow up into the gap between the shed roof and the fascia on the upper roof with heavy wind.. this would lead to a leak
 
#4 ·
With the dimensions that he wants (10' 4" rafter span) and 6'6" of headroom under the header at the low end, I've calculated the pitch would be appx. 1 7/16".
Am I understanding you correctly, that this will be a 1-7/16" rise on a 12" rise? Or is it a TOTAL of 1-7/16ths over the entire span?

If it's a 1-7/16ths - 12" rise, you can probably get by with steel roofing - provided there are no seams. It's not ideal, but would probably work fine.
 
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