Treated yellow pine is the best material to use in Houston for shade arbors and rain covers because of its treated to be more resistance to rotting. When rough-cut lumber is coated with a wood tone stain, the appearance can look very natural, and the color will not turn gray for many years. By using 8mm Twin walled Polycarbonate, any shade arbor can be made into a cover that will protect you from the rain, give you more shade, and requiring only a slight slope to the structure for the rain water to run off easily.