I need to build a Lean-to style shed that will attach to my shop. It will be 28' x 16' which is being attatched to a 28' x 24' shop. It will mainly cover a vehicle, small fishing boat, and riding mower . I will eventually close in two sides leaving the front open. I need to know what size lumber for the posts(4 x 4?) and how far do I space them (8'?). I also need lumber size and spacing on roof. If anyone has plans for this or advice, then I would greatly appreciate it.