Can I use the same exterior primer and flat paint I purchased for my house on my back porch which is a pressure treated wood?
No on the paint yes on the primer. The primer you can use on many surfaces, however you need a Porch & Deck Enamel for the deck. On a surface that will receive a lot of traffic and dragging, basically wear and tear, you want to use a stronger paint. Contact Sherwin Williams to talk about their new products that will work on the deck surface.