ACQ lumber has copper in it which can cause a reaction with regular metal fasteners. The chemical solution is soaked into the exterior of the lumber and penetrates about 1/8" to 1/4".
the Titan is hot dip galvanized and then powder coated with a durable finish to make it ACQ compliant if it ever contacts the preservative chemicals.
I won an inflatable 6 person inter hot tub. I have a large deck. 12x 20 on both sides of the house. With a header to the house and the deck was built 6
I'm putting a swim spa into an inground concrete bunker and will build a deck around it. I have been advised to keep the deck joists a minimum of 6 inches