When people think of hardwood floors, many associations can come to mind. These can range from fond memories of being a child lying on the living room hardwood at your grandmother’s to an exasperated homeowner dealing with a cupped or poorly installed mess. Hardwood flooring has been around for well over a century, and believe it or not, some of the first floors are still in use today. The finishes available nowadays would boggle the minds of the turn-of-the-century carpenters who installed some of these ancient floors.
The largest group of floor finishes belongs to the surface finish category. A surface finish is one that forms a durable and protective coating over the wood. Here, the durability of the finish varies based on the product being used, its application thickness and the duration and condition of the curing process. Historically, these finishes were natural varnishes and shellac. As modern chemistry advanced, so did the floor finish industry. Natural resins were replaced with alkyd resins, and those have been upgraded to mostly polyurethane resins. The modern field-applied urethanes are then broken down into various types based on chemical composition or how they cure. The top 4 are:
1) Oil-modified urethane is a solvent-based product and is very common and relatively easy to apply. It dries or cures through the evaporation of the solvent and its reaction with oxygen in the air. The durability is considered very good and it is available in various sheens, from high gloss to matte. Being oil-based, its color tends to shift toward amber hues with age. Dry times can run up to 8 hours and change with humidity levels.
2) Water-based urethanes, as their name implies, are water-based and cure and harden through the evaporation of the water component. These water-based finishes typically have a subtler odor than their oil-based counterparts and tend to dry a bit quicker. These finishes also do not yellow with age like the oil-based finishes. Some people find this appealing; others find them “milky.” These are often marketed as being greener than oil-based products and many times command higher prices.
3) Moisture-cured urethane is a bit more durable than both the oil-modified and water-based products. Moisture-cured urethanes are more difficult to apply and are oil-based, with satin or gloss sheens available. They are also formulated in non-yellowing and ambering types. Moisture-cured urethane has a stronger odor than the more common oil-modified products and is most often applied by professional flooring contractors.
4) Swedish finish or catalyzed urethanes are another of the oil-based products that are applied by pros. They are one of the most durable field-applied finishes, but they emit high volumes of VOCs during the drying and curing process. These finishes are comprised of a base and hardener and have quick dry times. Even though these have some of the most VOCs of any flooring product, they are usually installed by professionals with the proper training and equipment to render them safe.
Prefinished Surface Options
Prefinished flooring has gained immense popularity in the past decade or so. Leading this group is another newcomer to the surface finish family: the aluminum oxide finish. Those of you who are avid DIYers might recognize aluminum oxide as a type of sandpaper. The aluminum oxide used here is the same compound; it’s just processed differently. In aluminum oxide floor finishes, the aluminum oxide is ground into a very fine powder: not the coarse grains that are used in sandpaper. This powder is blended with the urethane and applied in many thin coats. The number of coats and the exact formulation of urethane will dictate its overall durability. I have seen durability test data range by factors of 4 to 5 for various versions of aluminum oxide finishes. When considering this finish for your pre-finished flooring product, feedback from other installations will ensure that the product you choose will stand the test of time.
Ceramic finishes are another new prefinished option and are very much like the aluminum oxide finishes, as they have ultra-fine particles of ceramic blended into the resins. These durable solids add excellent wear resistance and are economical options for many manufacturers.
Acrylic urethanes and acrylic impregnated woods are another prefinished option. These are similar to the polyurethanes in their resistance to wear, water and other spills. Some flooring manufacturers use UV-cured polyurethanes as their finish of choice; the high intensity UV light speeds the curing process and can result in faster and more efficient production.
These finishes that are factory applied are very durable, and unfortunately are not available for refinish work in the home. Drying ovens, UV chambers and production spray equipment are tools that flooring manufacturers use to get superior results. Field finish work is rarely sprayed and is therefore subject to minor imperfections.
Floor Finish vs. Furniture Finish
The finish applied to a floor differs from that which may be applied to furniture in a few ways. Both may be polyurethane products, but floor finishes are often applied in thicker coats and with less precision.
As a furniture maker and floor refinisher, I often refer clients to the “double standard” of expectation. Floors should be viewed and accepted from eye level in standard lighting. If you crawl around on the floor and expect the finish to be as perfect and flawless as the finish on your dining room table, you will be disappointed. While it is possible to have them look alike, the needed time and effort for that level of preparation is cost prohibitive.
Smaller sets of finishes actually penetrate the structure of the wood and provide protection and add beauty. Wax has been used as a floor finish for about as long as floors have been around. These are often used over basic penetrating oil or as a standalone finish. Tung and linseed oils have also been used as standard finishes for decades. Penetrating oil finishes are often combined with a topcoat of wax to add richness and depth to the wood’s grain and character.
When a wax or penetrating stain or oil is applied to wood, it soaks or is worked into the wood itself and the excess material is then removed. Waxes with solvent bases are very easy to apply and they dry quickly. These finishes are a little more work to maintain, but they are also one of the easiest to repair. The durability comes from the wood itself and varies by the characteristics of each species. Buffing an oil and wax finish can keep it looking like new, year after year, without the risk of chipping or flaking.
When I completed a large addition to my home, I used a traditional penetrating oil finish in my master bedroom. The hardwood flooring I chose was Jatoba, also know as Brazilian Cherry, and it is significantly harder and more durable than oak. I prefer the look of satin and low-gloss floors, and linseed oil alone yields a subtle sheen that is timeless in its beauty. Linseed oil also imparts a pleasant smell during application and provides basic protection in a room where heavy traffic is minimized. The low cost of a linseed oil finish is also a nice benefit. Polyurethanes can run $30-$40 a gallon; Swedish finishes $80-$100 a gallon; while linseed oil can easily be one-third of those costs.
Preserving Old Floors
Historic structures often have hardwood flooring installed and over time, these need some type of maintenance. To maintain a degree of authenticity, refinishing this flooring with catalyzed modern polyurethane would seem inappropriate. To provide some tips for this type of preservation or restoration, Bonita Mueller, a historical architect with the National Park Service, has this advice: “We have a lot of historic structures in the National Park Service which are open to the public. The areas that get a lot of wear are typically protected by some kind of sacrificial layer, whether that is carpeting, urethane, paste wax, etc. It depends on the significance and the use of the structure.
“I'd rather see projects start with a uniform surface that has been stripped and then either apply urethane or paste wax uniformly as the sacrificial layer. If you want to guard against flaking in the future, then paste wax would be the way to go -- or even paste wax on top of the new urethane. That might be overkill, however. Of course, the paste wax requires maintenance.”
Mueller urges people to think about the future when protecting the past. “Part of your solution needs to take into account the kind of maintenance you will have available on an ongoing basis. If it is practical and if this is appropriate to your final use, you might consider minimizing future wear by operational means once you have refinished your floor. You can request that people use booties that you slip over your feet before entering the structure.”
Maintenance and Care
The National Wood Flooring Association is an organization that provides information to all facets of the consumer and service industries that sell, install and refinish wood flooring. It understands that a beautiful wood floor is an asset to any home. To ensure that your investment will stand the test of time, the association recommends these 10 steps for proper preventive maintenance.
- Do not use sheet vinyl or tile floor care products on wood floors. Self-polishing acrylic waxes cause wood to become slippery and appear dull quickly.
- Use throw rugs both inside and outside doorways to help prevent grit, dirt and other debris from being tracked onto your wood floors. This will prevent scratching.
- Do not wet-mop a wood floor. Standing water can dull the finish, damage the wood and leave a discoloring residue.
- Wipe up spills immediately with a slightly dampened towel.
- Do not over-wax a wood floor. If the floor dulls, try buffing instead. Avoid wax buildup under furniture and other light traffic areas by applying wax in these spots every other waxing session.
- Put soft plastic or fabric-faced glides under the legs of furniture to prevent scuffing and scratching.
- Avoid walking on your wood floors with cleats, sports shoes and high heels. A 125-pound woman walking in high heels has an impact of 2,000 pounds per square inch. An exposed heel nail can exert up to 8,000 pounds per square inch. This kind of impact can dent any floor surface.
- When moving heavy furniture, do not slide it on wood flooring. It is best to pick up the furniture completely to protect the wood flooring.
- For wood flooring in the kitchen, place an area rug on the floor in front of the kitchen sink.
- Use a humidifier throughout the winter months to keep wood movement and shrinkage to a minimum.
Hardwood floors cover a number of rooms in my home, and as I installed all of this flooring myself, I have a personal connection to every board and staple used. Whether you have installed your flooring yourself or hired it out, you still appreciate its beauty. If you are considering refinishing or installing new hardwood flooring in your home, I hope this article has given you some insights on the finishes that are currently available. If you’re like me and enjoy the simple historical finish of a penetrating oil, or if you need the extra durability of an aluminum oxide finish, having reviewed some detailed information here, you can now make choices that are appropriate for your home and lifestyle.