I want to install a 10' tubular gate using a steel or aluminum gate posts. My question is what diameter do I need to use to keep it from sagging? I guess I should purchase a 8' length for my 4' fence but what diameter?
Any steel post of 3 or 4" (2" if it is a light weight gate) sunk in the ground 3 ft with concrete poured around will hold a steel gate and not bend. However, in my experience the real problem is, depending on your soil type and moisture, the weight will gradually pull the post over. Two solutions: 1) On the hinge side use two posts 4ft apart with cross bracing. 2) if the area is reasonably level, buy an wheel to put on the free end. It will take all the weight save you a lot of potential problems down the road.