I recently bought a house with a painted deck. Unfortunately for the seller, it did not sell fast enough. The deck was peeling badly and revealed poor condition deck boards. If you chose to paint anything, surface prep is critical. Paint is a surface coating and will not stick if the surface is dirty, moist etc. Looking at paints, notice the manufacturer's life estimates on a deck surface: even though manufacturers tend to claim higher than real world lives, most paints are not good for more than 5 years on a deck. Unlike stain, paint does not fail gracefully. It cracks and peels leaving a real mess. Repainting requires a massive cleanup and prep operation--complete removal of old paint ideally. The biggest drawback in most stain/sealer alternatives is the difficulty in removal when, inevitably, the surface needs refinishing.

In my last house, I had a 20 year old pressure treated deck that had never been coated with anything. After cleanup, I applied a semitransparent stain--a major endeavour since I had to apply coloring to all the deep cracks in the boards. I kept the house about 8 years after coating before selling and never got around to recoating. The finish faded, but faded gracefully. There was no peeling. Just less coloring. If I wanted to recoat, cleanup & prep would have been a quick cleaning and reapplication.

My last house had an existing PT deck that was painted brown. I repainted it about a year after I moved in, with some kind of exterior paint from HD, and didn't have any problems with peeling. A few years later the deck boards were bad enough (15-year-old wood problem, not 3-year-old paint problem) that I ripped them out and replaced them, then painted the new boards to match.

My last house had an existing PT deck that was painted brown. I repainted it about a year after I moved in, with some kind of exterior paint from HD, and didn't have any problems with peeling. A few years later the deck boards were bad enough (15-year-old wood problem, not 3-year-old paint problem) that I ripped them out and replaced them, then painted the new boards to match.