Ever want to know if you should use a primer or a sealer on masonry (brick, concrete, cinder block, stucco) surfaces inside your home? The short answer to the question: “It depends.”

That’s because conventional masonry primers and sealers are meant to do different jobs. A primer is supposed to provide a foundation for a masonry topcoat—especially when the substrate is not sound—and is usually pigmented, so provides some hiding in the bargain.

A sealer is usually a clear coating that fills the pores of a masonry substrate and forms a protective film on the surface. It also serves to tie the topcoat to masonry surface, by keeping the paint from being absorbed by a the porous surface.

The characters of primers and sealers reflect their different objectives. Primers are comparatively thick with relatively high levels of binder and pigment. They don’t penetrate, but they produce substantial films that stick strongly and enhance coating system performance and the ability to mask or hide a substrate.

Sealers, in contrast, are very fluid with little or no pigment. This combination of features lets them penetrate porous surfaces very readily to form protective coatings. The low solids (binder and pigment) content of a sealer results in a comparatively thin film, but one that offers excellent resistance to moisture and stains and is easy recoated.

So which product should you use on the masonry in your garage?…your bathroom?…your basement?…your mud room?…the so-called “transitional areas” in your house?

As a quick rule of thumb, if you have masonry that has already been painted at least once; a primer may be just the ticket. The substantial film it generates will fill in any damaged spots and give you an outstanding recoat surface.

If, on the other hand, you have fresh, unfinished masonry, a sealer may be the better choice. New masonry materials are extremely porous; painting them without first sealing them can be an expensive proposition. The pores will soak up topcoat like a sponge, requiring extra applications. A sealer can prevent this from happening. One caution: the films formed by a sealer are thin and clear so they don’t contribute much hiding. Sealers are also a good choice when all you want is a moisture barrier and don’t intend to repaint.

Still cannot decide what product to buy? Consider one of the many primer/sealers combinations offered by many paint manufacturers. These products are designed to serve in both roles and may provide all the performance you need in your home.

In all cases, be sure to always purchase the highest quality product you can. Painting masonry is labor intensive, and you’ll want to be sure the coating you choose performs well. New acrylic latex masonry sealers are available at many paint stores and home centers. These products do an excellent job without the strong solvent odors associated with solvent based products.

Of course, as always, the Paint Professional at your local store is an invaluable resource in helping you to choose the right product for your job.

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