Tips & Trends - 12/2009

Concrete Paint and Stain

Paint is a popular finish for concrete. Instead of all-weather carpet, or decking, paint is a great way to finish concrete porches, patios, pathways, garage floors, carport slabs and basements.

If you have freshly poured concrete, let it cure for 60 to 90 days in order to get the best adhesion. When you're ready to paint, the surface must be free of grit, grease, oil and anything else that would keep the paint from adhering to the surface. Once clean, the surface of the concrete should be lightly etched with a 25 percent solution of muriatic acid. The acid will do to the concrete what a light sanding would do to a wood surface. The paint will stick better.

Paint soon after cleaning and etching. You might consider a paint that contains a mildewcide to prevent mildew and fungus from growing on painted surfaces. Mildewcide is added to many paints in the manufacturing process, and can also be added later.

Rust stains on concrete may come up with a concrete cleaner that contains phosphoric acid. These cleaners come in liquid or gel form, and are easy to apply. Do wear gloves, protective eyewear and old clothing when using these types of cleaners. Peeling or flaking paint on the surface can be removed with a chemical remover, a sandblaster or a mechanical abrader. Remove old paint first, before cleaning and etching.

There are three types of paint for concrete: latex, oil and epoxy. Latex is the most widely used. It has excellent adhesion properties, it allows water vapor to escape, and it's easy to use and clean up. Latex floor paints for concrete are made to be applied directly to the concrete. There's no need to use a primer because the first coat serves as a primer and the second coat creates a uniform finish. A medium-to-long nap roller is best for application, with a paint pad or brush to cut in the edges.

Oil-based paints are a favorite for porches and patios because they offer a shinier, more durable, harder finish. Oil-based paint should be applied over a coat of oil-based concrete primer that's thoroughly dried. The application is similar to that of latex, but mineral spirits are used for clean up. Mineral spirits can be used to thin the primer a bit to improve penetration and the paint bond.

Oil paints can be applied over an existing oil finish that's clean and de-glossed with tri-sodium-phosphate (TSP) or a similar paint de-glosser. Chipping, peeling, or flaking paint should be scraped, sanded and filled with a patching compound.

The creme de la creme of concrete paint is epoxy. It's the most durable, and the longest lasting. Epoxy paint is popular in basements because it helps control dampness. Epoxy paints generally consist of two parts that, when combined, create a chemical reaction that results in an above-average bond that's highly resistant to abrasion.

Over time, all paint applied to concrete will bubble or chip, and have to be re-applied. This is especially true in areas exposed to hot car tires. Another option is concrete stain which is thinner and penetrates the surface more thoroughly for better adhesion. When dry, the stain looks more like pigmented concrete than a painted finish. The down side is that, because it's so thin, it doesn't have the resistance to abrasions and requires more frequent reapplication.

Concrete stains are applied to concrete surfaces prepared the same as for painting. The application is a bit different. The stain is mixed in five-gallon buckets and then mopped or rolled onto the surface.