I am in the process of renovating an attic and found a few rotted rafted tails left on and sistered to 2x8s. I was wondering if I could replace them, 1 at a time of course, with the roof on? The roof is relatively new and for whatever reason when it was replaced my grandma didn't have the rotted tails replaced. My plan was to cut them mostly with a sawzall and do the last bit with a hand saw to ensure that I don't slice the roof decking at all. then I will replace the rot and sister on both sides. I have done rafter tails before, went to tech school for carpentry, but the roof was always off. This isn't really an option in this case.

 

I wouldn't be afraid to do it with the roof in place. But unless the roof is steeply pitched, or you can work from the outside after removing the soffit, they will be buggers to get to (even if you're a tiny guy).

 

The roof is 4/12 and I can access them from outside when I remove the fascia.