New Porch Roof – tie to existing roof
Need advice on how to tie new rafters into old……
Remodel job calls for adding a new roof over 4 ft wide side deck. New roof is a 5 in 12 (about) w/ 6 foot (about) 2″ x 6″ roof joists. Birds mouth(s) of new roof joists are supported by 4″x 6″ beam that runs parallel to and above the side deck – simple enough. The part w/ the questions is the inside end of the roof joists where they meet the existing roof. The approved plans don’t specify the connection.
My current plan to affix the inside ends of the new joists to the existing roof as follows:
– Remove first few rows of comp shingles/felt to expose sheathing on the existing roof
– affix doug fir cleats to the existing roof sheathing directly over the existing roof joists, directly above the top plate of the wall supporting the existing roof joists – 1 cleat for each new roof joist with big ol stick nails and adhesive.
– cut out notch (female) from bottom of new joists to meet cleats (male) on existing roof.
– glue and screw joists to cleats and through sheathing into existing roof joists.
– Cover with felt, then ice and water shield, then new roof shingles (over old roof and new roof). This is in the Sierra Nevada so there is snow load to contend with.
Load from inside end of new roof joists will be almost directly over the top plate of the shear wall, and the engineer stamped the plans so I’m thinking that will work. A bit worried about the snow ripping the new roof off the old unless I make that connection bulletproof. Advice welcome.
Thanks
Wylie
Success = Work+ Risk + Luck, in that order. Muriel Seibert
Replies
What you propose sounds pretty good. When I worked with a framing carpenter though, we nailed a continuous 2x6 cleat where the ends of the new rafters would land on the old roof, rather than your method of separate cleats under each. That way you don't have to be so careful about the new rafters lining up with the old; and the one piece of lumber, rather than separate cleats would be easier and less likely to result in a "wandering line" when sighting along the joint where the new roof meets the old. We didn't worry about the nails (I'd use nails, not screws, just because they're easier, and nails are stronger in shear, which is the important factor here, rather than resistance to withdrawal) going through the sheathing into the old rafters. Glue is okay, but probably not necessary. If you use a wide board to nail the new rafters to at their top ends, you don't need to notch them, the cut you make to match the roof slope will and almost fully on the long cleat.
I'm hoping I'm understanding your situation--(for instance, you do mean rafters, rather than joists, as you stated?--rafters being the sloped members right under the sheathing and joists being the horizontal members the ceiling or soffit is attached to). I think the new joists (if indeed the new porch roof even has joists) could be helpful in keeping the new roof attached to the old though because they can act as ties to keep snow load from "spreading" the new roof by flattening it and making the eve bow out. If you use joists, I would use metal ties to reinforce this connection because of the snow load you mentioned. (Joists here would hold the new eve/fascia straight and parallel to the old.)
If this doesn't make sense, let me know and I will try to clarify. I'm sure other's will add their imput too, which may make more sense.
Not too sure what you mean by cleats.
Here are two methods I have used ;
one is to lay a 2x10 or 2x12 on the sheathing of the old roof parrallell to the outer beam, gluing it and lagging through into the old rafters, and then toenail the new rafters, with an angle ripped on them, to it and adding Simpson A-35s as well.
and the more bulletproof is to take off the existing sheathing at point of intersection and then fastening the new rafters directly to the old ones.
I would put down the ice and water shield first and then the tarpaper instead of the other way around
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Thanks Piffin and Danno for your advice - I like the big cleat idea rather than the fussy little cleat I was thinking of...my fussy furniture making past trying to intrude on a perfectly respectable roof remodel job.
Ice and Water first, before felt.....the idea being that the felt will eventually/maybe dry out if water gets shoved past it onto the ice and water shield, vs. the other way around (w/ ice and water on top) which is impermeable and would then create a mositure sandwich ?
Wylie
Success = Work+ Risk + Luck, in that order. Muriel Seibert
Ya, there is another ply for water to find it's way out again, and the I&W will be ther 'till the cows come home. Then the TP can act as a slip sheet so whenever they remove the shingles, they will come off instead of being bound at the seams. You create problems for yourself applying I&W over tarpaper too.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!