As Old Magnet assumes, red oak is specified in the blueprints from Cat for wooden canopies. The plans actually call for red oak frames and rails, marine grade 1/2 inch plywood for the roof cut into strips (to make the curve) and covered with cotton duck canvas held down with cypress battens and brass nails. All was specified to be painted with Hiway Yellow to provide water resistance to the canvas and protection to the wood. I used 5/4 red oak and clear varnished it, 5/8" Doug fir beaded ceiling board for the roof, the material that covered the top was Sunbrella synthetic canvas (yellow) and I used clear heart redwood battens I ripped from some 3/4" boards. The clear polyurethane (exterior grade) doesn't provide the weatherproofing you would assume, I would reccomend painting the exterior and clear poly the interior only if you can assure it won't get wet through a leaky window or door joint. Good luck.