Why is it so difficult to keep paint from peeling off of exterior wood decks?

There are two reasons: moisture and horizontal surfaces. Anywhere that snow can sit, or rain can puddle is a trouble area. Decks are all horizontal surfaces that snow can sit on. Strike two! Latex does not hold up well on horizontal surfaces. Moisture gets behind the coating and pushes is away from the wood. Decks are the only thing that we cannot warranty.