You can paint over old paint on a concrete porch. For the best results, you should first clean the surface and remove as much paint as you can. A power washer is helpful here, but you’ll also want to scrape as much of the old paint away as possible. Then you should prime the porch before repainting it.

It’s best to prime composite decking before painting. This promotes better paint adhesion, helps create a smooth finish, and can mean the paint job will last longer. Always follow the manufacturer’s instructions for application, allow ample primer drying time before painting (typically 24 to 48 hours), and thoroughly clean the deck boards to promote the best adhesion.

There’s no single paint that’s the most waterproof. Instead, there are several types of waterproof and water-resistant paints that suit different purposes. Epoxy paint, for instance, is commonly used to provide a waterproof coating to floors and decks. Masonry paint is an excellent choice for exterior walls. Meanwhile, there are waterproof acrylic paints that can be used for interior and exterior walls. It’s more about choosing the best type for what you’re painting instead of the most waterproof paint overall.

The longevity of paint on wood depends on factors like the quality of the paint, surface preparation, exposure to elements, and maintenance. Exterior paint on wood surfaces can last 5 to 15 years or more with proper care and maintenance. Interior paint tends to have a longer life span, often 10 years or more. Regular cleaning, touch-ups, and addressing any issues like peeling or cracking can extend the life of the paint.