Adding additional Rafters to existing roof structure
I am rehabing a ranch house constructed in 1974. The construction was done by the original owner as a self build using locally milled lumber for the majority of framing.
The house is a rectangle, two gable ends. Rafters to a ridge board. Ceiling joists acting as ties to keep everything in place. Full open span from wall to wall in attic. Pitch is 5 / 12. Framing of rafters is self milled looks to be mostly heart wood true 2 x 6. Spacing 24″ on center. Span is 13′ 2″. Definately not to code but have been there for almost 50 years and only some minor deflection that I am not looking to fix.
I want to beef up the roof and it looks like the best way is to add new 2 x 6 rafters to make the spacing 12″ on center. The other option is to sister the rafters which I have plenty of details on. Adding the rafters appears to put the house on par with current 2021 IRC.
Can I add the new rafters rather than doing sisters? I have full access to do this. The house has been stripped to framing on the interior so I can slide in new rafters and hang them from the ridge board.
The ridge board has also gotten additional support. The house is 28′ wide and I have decided to reframe the interior in a way that puts a load bearing wall from the ridge board down the center. The center framing has piers all along the center to support that wall. Because of this I’m not concerned about the strength of the ridge board.
Just haven’t seen anything about adding rafters to old construction, just the sistering to add strength. I need to do something now that it is open for peace of mind.
Any suggestions on best way to do this or if it even makes sense would be appreciated. Just can’t find anything referencing adding additional rafters.
Zone 5, snow load 30lbs, high prairie, and dry.