There has to have been some major roof leakage or insect damage to have caused this much damage.
Sistering is not going to work in this case.
No one knows where you are so it's hard to know what type insect could have caused it.
Any real exterminator can tell you what caused it.
its not insects, its the only rafter in the attic with an issue. I think it was a bad piece of wood or maybe a blow to the roof. It is close to a roof vent, so perhaps moisture was an issue. I don't know.
A forum community dedicated to Do it yourself-ers and home improvement enthusiasts. Come join the discussion about tools, projects, builds, styles, scales, reviews, accessories, classifieds, and more! Helping You to Do It Yourself!