Hi,

I am going to help a friend insulate and finish her attic. 

The building is a 100+ year old farmhouse, with framing quite different from current practices. 

Full dimensional 2×4 rafters, 36″ o.c. spanning 10′ from a 4′ knee wall to the peak. There is a collar tie roughly 6’6″ up. 

I have attached a picture. 

My friend wants to raise the collar ties to 7′ because her husband is 6’5. I’m thinking of sistering on 2x6s to the existing rafters and then cutting the old collar ties, moving them up and through bolting them back together. 

My other thought was adding new 2×6 rafters at 18″ o.c. to halve the current spacing. 

The attic will be insulated with closed cell spray foam and then finished with pine paneling. 

Any thoughts? Better approaches?