I was going to install skylights into my 16" on center rafters and ordered 14" wide skylights so I could drop them right in-between the rafters. However, yesterday I popped my head in the eave and looked up and saw that the rafters were actually sistered right above the eave, and now I’m concerned that my skylights aren’t going to just drop right in if the overlap of the rafters is more than a few feet.
Can anyone comment on this?
Generally, when you have overlaps in rafters, it doesn’t pass 16" where they meet.
Since you’re going to have to install double headers for the skylight anyway, it looks like you’ll also have to sister rafters to the sides of the already sistered rafters that don’t have them (because the sistered rafters alone won’t be strong enough as they’ll be interrupted jack rafters.
In other words, continue to double up the rafters where you plan to install the skylight and you’ll be more than ok. After that, it’s a matter of which rafter you may need to cut out for the length of the skylight if you need the extra space, but because you know have two fully doubled up sides, this should be no problem.