How to Apply Water-Based Urethane Finish to a Hardwood Floor
Previously published in Tomorrow’s Contract Floors
Eco-friendly, water-based urethane finishes for hardwood floors are hot right now for a reason. They look natural, dry faster, level better, foam less, clean up with water instead of solvents, and don’t always require intercoat abrasion. Their low levels of volatile organic compounds (VOCs) also mean they are safer to use than solvent-based finishes.
Water-based finishes dry in just 2-4 hours. That means you can apply two coats per day. However, because they dry fast, you’ll need to work quickly if the weather is warm and the humidity low. Therefore, it’s a good idea to have some experience finishing hardwood floors before trying your hand at water-based finishes.
Water-based finishes fully cure in 4-7 days compared to the 14-30 days needed for oil-based urethanes.
Get Tooled Up
Before you begin to work, get your tools ready. You’ll need a sander or a rotary buffer for sanding and screening. It’s probably also a good idea to have a shop vac on hand for keeping your work area clean.
While there are a variety of ways to apply the finish, it’s best to use the applicator recommended by the finish manufacturer to ensure proper coverage.
Indirect air circulation is important for water-based finishes. However, you don’t want air blowing directly across the wet finish because it could cause it to dry too quickly. If this happens, it won’t lay out evenly and you could end up with application marks. Higher humidity can actually work in your favor because it creates more forgiving conditions for applying water-based finishes.
Testing for Dryness
Testing for dryness is important if you want a successful finish. If the wood isn’t dry enough, the urethane finish won’t bond properly. The same is true for each coat of sealer or finish. If not sufficiently dry before you apply the next coat, you could have bonding problems.
We recommended using pinless wood moisture meters because they don’t damage the floor. Because wood flooring comes in a range of thicknesses, you should use a pinless meter with a variable depth setting.
Wagner’s Orion® 930, 940, and 950 dual-depth, pinless wood moisture meters are among the most accurate meters used by wood flooring professionals today. They even include quick, easy, on-site calibration, an industry first. If you finish floors for a living, they’re a great choice.
How to Apply
Get your tools ready and clean/prep your floor. During the application process and until the finish is dry, the room should be over 65℉. It’s best to follow the finish manufacturer’s recommendations for application. Contact them if you have any questions about the product.
Use your pinless moisture meter to make sure the wood floor is at its equilibrium moisture content (EMC) before beginning. Use the brush attachment on your shop vac to clean the work area from dirt and dust. Finish by wiping down the floor with a soft, clean, lint-free rag.
Apply one coat of water-based sealer and allow it to dry. Since some stains are considered sealers, follow the manufacturer’s recommendations for application. Note that oil-based stains take longer to dry. Allow a minimum of overnight and even longer for heavily pigmented colors.
Before continuing, set your pinless moisture meter to ¼-inch mode (shallow depth scanning setting) and test to make sure the floor is dry.
Note that most finish manufacturers don’t recommend buffing/abrading their water-based sealers.
When the moisture meter indicates the floor is dry (should be close to the reading you took before you applied the sealer), apply the first coat of finish and allow it to dry.
In a three-coat, water-based finish system (seal, finish, finish) you apply the sealer, let it dry for about two hours, and then you apply the first coat of finish. After that’s dry (use your meter to make sure, preferably using the shallow mode if you have a dual-depth pinless meter from Wagner Meters), you apply the second coat.
Now you’re going to use your moisture meter again to make sure the second coat is dry. When it is, the floor is safe for light foot traffic.
The general rule is to give the final coat of water-based finish 24 hours to dry before placing furniture on top of it. However, we recommend giving it time to fully cure (4-7 days) before placing rugs and furniture on it. This is because they block the ability of the finish to fully ‘’off-gas’’ the chemicals contained in the product. If these chemicals get trapped, they can cause the floor to discolor and even reduce the finish’s performance.
Note that although a water-based finish takes 4-7 days to cure completely, it will typically be 75-90% cured after 24 hours.
The Finished Floor
Congratulations! You now have a beautiful new wood floor that’s both durable and eco-friendly. If you’ve used your pinless moisture meter at each stage of the process, your finish will look great and be problem-free for years to come.
For more info about how pinless wood moisture meters can help you avoid moisture-related issues in flooring installations, call Wagner Meters worldwide toll-free at (844) 574-0228.
Jason has 20+ years’ experience in sales and sales management in a spectrum of industries and has successfully launched a variety of products to the market, including the original Rapid RH® concrete moisture tests. He currently works with Wagner Meters as our Rapid RH® product sales manager.
Last updated on January 10th, 2022