One of the biggest elements in the lifespan of a deck is sun exposure. When a deck is exposed to full sun it can have a damaging effect that can shorten the life of the wood. Harmful UV rays break down the wood fibers and cause discoloration, graying, and fading. When a deck becomes severely sun damaged the decking boards can warp, crack, and split causing dangerous splinters and a very unappealing look. In extreme cases UV damage is irreversible and cannot be repaired.
The best stain for full sun decks is one that has a heavy pigmented formula that acts as a sunscreen and blocks damaging UV radiation. Most of the stains that are best for full sun decks will penetrate deeply into the wood pores. For example, Defy Extreme is an excellent waterborne product that uses nanoparticle technology and heavy resins to help reflect harmful sunrays.