Does composite fencing sag?

Whether or not a composite fence sag is dependent on the design of the fence. Composite fences that do not use metal reinforcement for rails are most likely going to sag over time. Trex Fencing is built with a sturdy aluminum bottom rail that supports the weight of the fence. The rail is covered by composite boards, hiding the aluminum. This gives you the aesthetic wood-like appearance of Trex with the reinforcement necessary to protect the fence from sagging. 

Our installation resources offer more information, and can be accessed by visiting https://www.trexfencingfds.com/resources/seclusions-install-guides/