1920's Bungalow Shed Dormer
I am looking at adding a Shed dormer to the back of my 1928 Bungalow in Portland, OR. I need to replace the roof anyway, so I was thinking while I'm at it....
Anyway, I have a couple of issues:
1. Upon examing the existing structure of my roof I found I have rafters that are 2x4's on 24" centers. If I add a dormer the full length of the house out the back I will be using 2x10 or 2x12 rafters. The span from the ridge to the exterior wall is about 17'. My question is how do I tie these new rafters into my existing ridge? And, what do I need to do to the side of the house that I am not touching? The roof is not sagging right now, but what do is the city going to require of me as far as supporting that side and more importantly am I going to have to meeting newer insulation requirements? I forgot to mention that the attic is already finished. I could sister in new rafters, but would have more dry wall to take out and I don't know how thick I would have to go to get the R-38 rating that I think they are looking for.
2. My existing roof pitch is 7in12. The new dormer looks like it would have to be a 2 1/2 in 12 to make it worth it. It I want to do comp. roof, am I just asking for trouble? Even if I use a snow and ice shield on the entire dormer roof?
Let me know if you have any thoughts.