We have just purchased a home that is U shaped, in the center of the U is a concrete area that is not covered. We are wanting to continue both sides of the roof and cover the area. the rear will meet an exsisting fire place and wall. It is a 21x20 area-- want to leave it with the beams exposed. Suggestions on tieing into the exsiting rafters and hanging the center beam that will be attatched to the fireplace.