Most concrete stains on the market today, whether they are water-based or chemically reactive (acid-based), can be used on both interior and exterior concrete. So how do you determine the best product to use for a particular project? The factors that come into play aren’t much different than those you would consider for indoor vs. outdoor painting: exposure conditions, the look you’re trying to achieve, ease of application, and safety and environmental concerns.

A bowling alley floor colored with water-based stains. Impressions Decorative Concrete, Inc in Lutz, FL

Indoor Staining

Is the stain safe for indoor use?

Read the safety precautions provided by the stain manufacturer. For indoor projects where ventilation is poor, concrete stains with a low VOC content will be your best choice. Some chemical stains contain solvents and corrosive components that can cause eye, skin, and lung irritation.

What are the cleanup requirements?

Chemical stains can be messy to use indoors because you must scrub the slab thoroughly after applying to remove any stain residue, followed by rinsing with clean water. Then you must collect all the residue with a wet vac and dispose of it safely (see Acid Staining Basics). Water-based stains are easier and safer to apply indoors because they are free of solvents and acids, and they don't require neutralization or rinsing.

What look are you trying to achieve?

If you want to match an existing color scheme or make a bold design statement, water-based stains will give you an endless array of color options and, like wall paint, can be mixed to create custom shades. (See how water-based stains were used to add vibrant color to this bowling alley floor.) If you want to achieve rich earth tones with natural marble-like color variations, chemical stains are often the best choice, as long as the proper precautions are taken during indoor application. On this residential floor project, chemical stains in dark walnut and antique amber were used to create an appealing vine pattern.

Is your floor slab emitting moisture?

For the best results, concrete stains should be applied to interior slabs that have a low moisture-vapor emission rate. Some manufacturers recommend performing a moisture-vapor emission test to check for suitability.

Outdoor Staining

Is the stain UV- and abrasion-resistant?

Most water-based and acid stains for exterior concrete are UV- and abrasion-resistant. However, because acid stains deeply penetrate and chemically react with the concrete, they may provide greater resistance to fading and wear over time. Both types of stain are permeable to water vapor and act as good barriers to moisture penetration.

An acid stained patio with a scored diamond pattern. Holland Decorative Concrete in Rockwall, TX.

Will acid stain kill vegetation and grass when used outdoors?

For outdoor projects, the fumes from acid stains will not pose much of a problem. However, the residue and runoff from rinsing off the stain must be contained because it could harm the grass and surrounding vegetation. Water-based stains don’t require rinsing and any residue can be safely cleaned with soap and water.

Does the color work with your landscape and home exterior?

If you want to replicate the appearance of natural aged stone, chemical stains will react chemically with the mineral content of the concrete to create a beautiful mottled appearance (see this acid-stained patio). Water-based stains are non-reactive, so the color tends to be more opaque and uniform. However, water-based stains will give you more color options and the ability to customize colors to coordinate with the color scheme of your home exterior. For this residential driveway project, solid-color water-based stains were used to match the home’s existing design scheme.

Use a Good Sealer

Whether you’re staining indoor or outdoor concrete, all stained surfaces should be protected with an appropriate sealer, which is determined by the type of stain, exposure conditions, and the level of traffic. Not only does the sealer provide protection from day-to-day wear, it also enhances the color and determines the gloss level of the finish. For indoor projects, lower gloss levels tend to be easier to clean and won’t show wear or surface scratching as much as high-gloss sealers. Learn more about choosing the best sealer for your project.