Water-based urethane finishes are becoming more popular for hardwood floors. If you’ve never used one before, you’re sure to appreciate the low amount of volatile organic compounds (VOCs), and your clients will love the more natural look. During application, you can also expect water-based urethanes to dry faster, level easier and foam less, and they clean up with water instead of solvents.
With a drying time between coats of about two hours, you can apply four coats of water-based urethane in a day, and a full cure typically takes 24 hours. Faster drying does mean you need to work quickly—especially in warm, dry weather—so you will need some experience with finishing floors before you attempt to use them.
First, you’ll need a sander or rotary buffer for sanding and screening—preferably one with an integral vacuum. You’ll also need a good shop vac for keeping the place clean. Tools for application are the same as they are for oil-based products: a T-bar applicator and a pad painter. A fan is useful to increase ventilation, and if the ambient conditions are humid, a dehumidifier can help speed things along.
Testing for Dryness
The most important tool for ensuring a successful finish is a wood moisture meter. All wood flooring contains moisture, and if the wood isn’t dry enough, the moisture can prevent urethanes from properly bonding. The same holds true for each coat of sealer or finish. Each coat must be sufficiently dry before you apply the next coat.
Some moisture meters allow you to measure the equilibrium moisture content (EMC) of the wood. With consistent environmental conditions, this is the state that the wood will “live” in. Wood flooring comes in a range of thicknesses, so for hardwood floors, a moisture meter with a variable depth setting is best. To avoid damaging the floor, make sure to use a pinless moisture meter.
The Wagner Orion 930, 940, and 950 dual-depth, pinless moisture meters are perfect for this type of job and feature on-site calibration—an industry first. Once you have all your tools lined up, the application is the same as it is with oil-based products. There’s no need for additional skills or tools.
Plan to apply the finish on a warm, dry day. Be sure the temperature in the room remains above 65 degrees Fahrenheit through the whole process and until the finish is dry. The first step is to check the wood floor for EMC. Use the moisture meter and set it to the recommended depth for the floor thickness. If the floor isn’t at EMC, you will need to do some remediation. Always be sure the moisture condition of the floor is good before you start.
Always make sure the area is free of dust and dirt. Vacuum the floor with a shop vac and brush attachment, and finish by wiping down the floor with a clean, soft, lint-free rag.
Apply one coat of sealer and allow it to dry overnight. Ensure that the pinless wood moisture meter you are using features a shallow-depth scanning setting. (If you are using an Orion 930, 940, or 950 pinless wood moisture meter, ensure that the meter is set to 1/4” mode.) Scan the floor with the moisture meter to check for moisture content. If the floor isn’t at the proper moisture content yet, you’ll need to give it more drying time.
When your meter indicates the floor is dry enough (close to the same reading as the wood was prior to the application of the finish coat), lightly sand it using a buffer or sander. Sanding reduces the grain raised by the sealer. If you skip this step, the grain will show through the top coats of finish.
Once you’ve lightly sanded the sealer, vacuum the floor thoroughly and wipe down with a clean, damp cloth. Apply the first coat of finish and allow at least two hours to dry. Scan the floor with the moisture meter. When the reading reaches earlier moisture content readings, the floor is dry enough for the next coat.
If you apply the next coat within 24 hours, there’s no need to screen. Repeat the process for the remaining coats, usually two or three more, making sure you scan with the moisture meter before each coat. When the moisture meter shows the last coat is dry, it‘s safe to place furniture on the floor. In 24 hours, the floor will be fully cured and ready for use.
Congratulations! You’ve finished a naturally beautiful, durable new floor. Your clients will thank you, your reputation will thank you, and your Angie’s List posting will grow by another happy review. And as long as you tested the floor with a moisture meter at each stage of the process, the finish will look great and remain problem-free for years.
For more information about how pinless wood moisture meters can help you avoid moisture-related damage in your next flooring installation, visit