Hello I would like to add some unconditioned storage room in my attic,maybe later on down the road add on a room and a dormer. My house was built in 1948 2x4 roof rafters 24inches on center 17’7inches long, peak height is 9 foot. Ceiling joist are also 2x4. Currently there are braces from mid way through the rafter to the center of the attic no purlin. I would like to remove the braces and add a knee wall and collar ties in its place. I don’t know how high the knee wall needs ton and how low the collar ties will be to support the roof. I can send pics if needed but the site won’t let me upload them.