How should I extend my rafters and roof sheathing, which are currently flush with siding?
WolfDaddy
| Posted in Construction Techniques on
There is a shed roof on an addition off the back side of our garage. The back wall of the garage is 22′ wide. The addition is 20′, so the side walls of the addition are one foot in from the corners of the garage. The roof of the addition does not overhang its side walls. The siding goes up to the top edge of the rafter and the plywood roof sheathing goes out past the edge of the rafter to the face of the siding.
I will be shingling and residing the entire garage as soon as our Chicago weather is good enough. I’d like at least a small overhang on the side walls. I was thinking when I remove the siding I would simply nail three 2x6s onto the existing 2×6 rafter. That would give me about a 4″ overhang after installing the new siding up to their lower edge.
My question is, do I need to replace the roof sheathing and run it out to the side of the outer most new 2×6? Or, can I trim the current sheathing off at the edge of the original rafter and then install the new 2x6s with their top edges flush with the top side of the sheathing? Actually, I would probably use 2x8s and rip them to width to equal the current 2×6 plus the thickness of the roof sheathing so that they line up with the top side of the sheathing and the bottom edge of the original rafter.
Replies
You did not say how deep your addition is.
if you are removing the siding and will have access to the rafter, it might be better to build up a ladder and frame the overhang, instead of tripling up expensive framing lumber. You could make the overhang 6 or 8 inches, if you want to keep the edge out of the sight line from the front of the garage.
I would replace sheathing to the next rafter at least, to help tie it together.
https://basc.pnnl.gov/resource-guides/framing-gable-roof-overhangs#edit-group-description
UncleMike42 - I thought of doing a ladder. I was concerned that attaching it just to the side of the outer rafter vs going to the second rafter (your attachment fig 2 vs 3) would not provide enough support for the downward weight of snow or someone walking on it. From your attachment, I see that I should be OK as long as I limit the overhang to 8 inches or so. Thanks for the suggestion and drawings. I'll have to decide how much overhang will look best. Probably match the sides of the garage, which is less than 8 inches.
As to the depth of the addition, it's about 12 feet. The rafter is just short of 14 feet.
You can use some clamps to help hold the new ladder in place while you fasten it.
Continuous roof decking will provide quite a bit of strength to the assembly, if it extends to the next joist (better to the one after that)
2x4 should be plenty. keep in mind the span here is only the width of the overhang, not the 12 feet of the roof. The joist you hang it on is likely supported in multiple places by the wall below.
Check out the retrofit tab at the URL posted earlier.
https://basc.pnnl.gov/sites/default/files/images/ReroofOverhang-F7-GableOvrHg.jpg.png
UncleMike42 Thanks for the additional info. I like that I can get the overhang to match the size on the garage using your method. That will look better than the smaller overhang I would get using my original idea of stacking 2x6s.
H-clips are an architect's or engineer's call, not a code requirement. 7/16" OSB very commonly spans rafters 24" on center without clips. If you think the sheathing is over-spanned, recommend evaluation by an engineer. When clips are installed every 24", the roof sheathing panels are touching every 24".