I have a 17L x 10W wood deck. It is 12 feet above ground supported with three 4X6 posts. The joists are 2x10. There is no cantilevering (i.e the outside band sits on the 4X6 posts. Structurally, everything is solid with no rot. I want to extend the deck by 2 or 3 feet to make it 17 x 12 or 13. How can I extend this by using the existing structure, including joists and posts without adding new posts?