I've got a problem I'm looking for a bit of help with -
My house (100 years old) has 2x4 rafters supporting the roof that are entirely unsupported in the middle. They run a 14' angled span from their base to the peak, where they meet in a butt joint. Aside from a few cross and vertical supports added by previous owners of my home, there is no interior support for those rafters.
Because of that, a large number of those rafters have flexed fairly significantly over time. A smaller number (half a dozen) located near the middle of the roof have snapped or cracked. I'm planning on sistering 2x6's to the snapped rafters full length so the roof is supported entirely by the 2x6's at those locations. I'm also planning on adding vertical supports every third or fourth rafter to the horizontal rafters below them, directly above interior walls for added support, although I expect the double 2x4 (true size, they're old) and better supported horizontal rafters to handle the load better.
All of that I'm in good shape about, my question however is twofold as follows:
Should I attempt to correct the flex of the roof at all when sistering / adding vertical supports?
If yes to the first question, what method should I use to straighten the rafters while I put the sister boards / vertical supports in place?
I appreciate the help!