I have to upgrade the rafters on the cathedral ceiling side of my house from 2 x 6s to 2 x 10s to meet code. Code requires the ridge board to be as wide as the cut face of new rafters. Does anyone know if the sistered ridge board design shown in attached drawing would be allowed? It is not quite as wide as cut rafter face, but I can add straps or brackets, and the rafters above the upper bearing wall do not have be 2x10s because of the shorter span.
Thanks,
Tom
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Replies
Question for you: if the length of rafters above the upper bearing wall don't have to be 2x10, why is there a concern with the ridge? Unless I'm missing something, you should be able to sister 2x10s to only the lower portion of the rr's that is over your cathedral room, in which case those 2x10s wouldn't extend up to your ridge. Or am I misreading you on this?
Tom,
If I only put 2x10s to upper bearing wall I will have either a 4" drop in roof line at upper bearing wall, or a change in roof line pitch at upper bearing wall, which won't look good. Also, 2x6s are quite bowed and have some rot and need to come out.
Thanks,
Tom
Ah, gotcha. So you're doing this all from above then, with a completely stripped roof down to the rafters, and actually removing the cathedral-side rafters and drywall as well?
I'd assumed you were having to sleeve in rafters from beneath, with the drywall removed and all the roofing and sheeting intact.
What triggered the need for this change?
If that's the case, where you're doing this from above with a stripped roof and leaving existing rafters in place, I'd just butt them to the existing ridge board and add blocking for edge nailing of the roof sheeting at the new 'ridge' location. I attached a scale drawing of what I'm thinking.
Just a heads up that drawing things to scale is super helpful and reveals lots of things you wouldn't always see until you go to build it. Which allows you to plan your moves and materials better. If your pitch is indeed a 3:12, an example of the scale drawing thing is that it shows that a 2x10 sistered flush with the bottom of a 2x6, using the cut shape you're thinking of, requires no additional board at the existing ridge because it's only around a 6" long end cut.
I'd expect an engineer might want Simpson A35's at each rafter-to-ridge connection, and maybe even at the new ridge blocking, but maybe CT_Yankee on your thread here can offer some input.
Thanks Tom, The roof pitch is 5/12 and the current 2x6s are bowed and some are partly rotted due to leaky skylights. The popcorn ceiling has water damage and the asphalt shingles are old too! So it is going to be a completely new roof drywall to shingles. The 2x10s will also allow for much better insulation. The good news is I bought the house very cheap because of these issues, and I enjoy a challenge...? I thought the building code referred to a normal rafter cut and not a double cut. Thanks again, Tom
Maybe talk to the Inspector and get his/her input
Thanks, I usually go to inspector with a proposed approach for his comments and not use him as a structural engineer, which he doesn't seem to appreciate.
Are your existing 2x6 rafters over the living room one piece (~24'+/-) from outside wall at the sun room up to the ridge over the attic?
Why not lower the ceiling over the living room and run the 2x10s only from the sun room wall up to the bearing wall at the 2nd floor closet?
I assume you're expecting an almost total tear-off of the roof with what you're proposing.
BTW, I suspect that the 2x10s can still be adequate with a carefully notched bottom at the lower & upper plates. A structural engineer (like me) could evaluate and sign off on this.