Epoxy and polyurethane are among the most popular finishes for concrete and other types of floors in commercial and residential structures.
The two products are also commonly used to finish countless other surfaces, including countertops and furniture.
It can be challenging to decide which way to go when choosing polyurethane vs epoxy for your next woodworking project with such close similarity.
This article compared the various key features likely to influence the choice of either of them to help you decide more easily for your next project.
What is Polyurethane?
It is a synthetic resin commercially available in liquid form. Two main types of polyurethane in the market include water-based and oil or solvent-based formulations.
Water-based poly can be thinned with water and used as a wood sealer. On the other hand, oil-based polyurethane thins with solvents such as mineral spirits, depending on specific project requirements.
Both water and solvent-based polyurethanes form a tough, flexible, and durable coat on wood, concrete, metal, and other surfaces they are used on.
Polyurethanes are highly stable, with remarkable durability and heat tolerance. You can also find them in a wide range of sheen levels, from high-gloss to matte finishes, with semi-gloss and satin in between.
Pros and cons of poly
Polyurethane is one of the best finishes for wood and other surfaces for many reasons, including these.
What We Liked Most
- The product is highly durable
- It boasts outstanding heat resistance
- It has superior chemical resistance.
- It forms a tough coat with significant resistance to abrasion.
- Polyurethane surfaces are highly resistant to water and moisture.
- Most polyurethanes go on clear and stay that way unless they are exposed to sun radiation.
What Could Be Improved
- Polyurethane can give the wood an amber tint, especially when exposed to direct sunlight.
What is Epoxy?
Epoxy is a resinous organic compound consisting of two parts that typically combine to form a hard-wearing solid as a result of a chemical reaction. The two parts making up an epoxy include a resin and hardener, or curing agent.
Epoxies come in different types, some of which have nearly zero volatile organic compounds (VOCs).
The range of uses of epoxy in woodworking is as varied as polyurethane, except it can be used as an adhesive which is not one of the uses of poly.
Epoxies readily adhere to different substrates, making them an excellent adhesive. When used as protective topcoats, they dry to form a hard coat that is durable and highly resistant to physical impact.
Epoxy resin pros and cons
Like any substance, epoxies have some significant advantages and limitations that make them suitable for their different uses.
What We Liked Most
- Epoxies are significantly chemical resistant
- They have excellent moisture and humidity resistance
- They dry to form a tough protective coat on a wide range of surfaces
- They have excellent adherence capabilities
- Epoxy is relatively cheaper than polyurethane
What Could Be Improved
- The material chalks and fades over time
Epoxy vs Polyurethane Side by Side
Epoxies have numerous similarities to polyurethanes, albeit with a few notable differences.
Polyurethane vs epoxy: Common uses
Epoxy has a wide range of uses in and outside woodworking. It provides an excellent seal for wood, and coating for countertops, wooden boards, furniture, hardwood floors, and concrete floors.
It is also used as an adhesive for attaching pieces of wood and other non-wood materials or for replacing damaged parts, especially in wood. Additionally, epoxy can come in various shades used to color metal surfaces.
On the other hand, polyurethane is typically used to coat surfaces of wood, metal, concrete, and more. It can also work as a filler for cavities in wood. Like epoxy, its most common uses are on concrete and hardwood floors.
Epoxy vs polyurethane: Abrasion resistance
Polyurethane forms a very tough coat when dry. This quality makes it resist abrasion pretty well, so polyurethane surfaces can usually remain immaculate even in scratch-prone environments.
It also absorbs physical impact from hard-hitting objects without forming dents. For this reason, surfaces coated in polyurethane tend to remain sound for many years.
Epoxies equally form hard coats but are more vulnerable to scratching and denting than polyurethane finishes.
Epoxy vs polyurethane: Price
Polyurethane often costs slightly higher than epoxy. Epoxy is generally a cheaper alternative, even though the prices vary with brand and formula.
Based on their product policies, some manufacturers will have their epoxies priced slightly higher than the average market rate. So you can expect the price margin between polyurethane and epoxy to be negligible in some cases.
Nonetheless, other determining factors should come above the price when choosing between polyurethane and epoxy for your project.
However, it could be a significant consideration if you are on a budget and the relative advantages of polyurethane are of little effect.
Epoxy versus polyurethane: Durability
Both epoxy and polyurethane are significantly durable. However, it is easier to draw a difference between them when you consider the specific application.
For instance, when the products are used for adhesion purposes, epoxy comes on top. The compound forms some of the strongest bonds with virtually any material.
These epoxy bonds are robust and tend to be far more durable than bonds by other adhesives, including polyurethane. Epoxy also holds up well against compression force.
This is why they are a favorite finish for concrete floors in commercial establishments that frequently carry heavy equipment and weights from other hefty objects.
Despite epoxy being harder than polyurethane, the latter tend to last longer due to its flexibility. Polyurethane remains significantly flexible even when dry, making it withstand impact and remain sound for a long time.
So if you use polyurethane on one floor and epoxy on another, you can expect more years on the polyurethane floor than on the epoxy one.
Polyurethane versus epoxy: Chemical resistance
Epoxy and polyurethane are both resistant to chemical damage, but they resist chemicals differently from one another. Some chemicals react with polyurethane more than they do epoxies.
For instance, a concrete floor covered in epoxy will be more resilient to certain commercial acids than polyurethane-coated concrete floors.
If you are finishing a commercial establishment likely to have chemicals like sulfuric acid lying around, you may be better off with epoxy than poly.
However, for residential applications prone to alkali and solvent spills, you may want to consider polyurethane over epoxy resin. This is because polyurethanes tend to be more resistant to these chemicals than epoxy and will remain sound despite exposure.
So it is important to consider whether your project is more prone to acids or alkalis and similar chemicals when deciding between epoxy and poly. Admittedly, this consideration will be secondary in most cases.
Epoxy vs polyurethane: Humidity and moisture resistance
Epoxy is highly resistant to humidity and moisture. So if your project is located in a place that constantly experiences high moisture or humidity levels, epoxy will be a more suitable choice over polyurethane.
In comparison, polyurethane coatings tend to be sensitive to humidity and moisture. The recommended relative humidity level for polyurethane is below 70.
Relative humidity beyond the recommended levels can affect polyurethane during application and afterward. Applying polyurethane in a high humidity environment can affect the clarity of the polyurethane finish.
Constant exposure of the finish to moisture significantly reduces its service life. However, in most cases, epoxy will last longer than poly if the two are subjected to moist or humid environments.
So, it may help to consider the moisture condition in your area when choosing between the two finishes.
Poly vs Epoxy: Curing time
Polyurethane may be your best choice if the speed of drying and curing matters to you. Often, it will get fully cured in about half the time epoxy takes to cure fully.
Polyurethane cures faster than epoxy in nearly every situation, making it a better choice for time-sensitive projects. In addition, it can allow you to start using your finished project sooner than you would with epoxy surfaces.
Polyurethane takes about 24 to 48 hours to dry fully. If you use a water-based poly on your project, you can expect it to dry fully in about 24 hours, while solvent or oil-based polyurethanes take as much as 48 hours to complete drying.
Epoxy, on the other hand, takes about 72 hours to dry fully. Additionally, you must allow the resin to complete drying before sanding it or putting it to use. Otherwise, the finished surface may get contaminated.
Notice that both polyurethane and epoxy will take at least 30 days to be fully cured after application. High-VOC products like oil-based polyurethane continue to release gases throughout this curing period and should be approached with care.
Epoxy vs polyurethane: Tolerance to temperature changes
Thanks to its flexible quality, polyurethane-coated surfaces can easily adjust to extreme temperature changes.
For example, if the day changes from extremely hot at midday to chilly in the evening, the coat of polyurethane will simply expand and contract with the change.
The same rule applies in kitchens or food preparation facilities where heating equipment can rapidly increase ambient temperatures before it gets pretty cold again.
In any of these instances, the flexibility of polyurethane comes in really handy, ensuring the appropriate expansion and contraction instead of breaking under the rapid temperature change.
In contrast, epoxy coatings tend to be tough and relatively inflexible, so they have difficulty responding to rapid, extreme heat and cold.
Their limited tolerance to thermal changes can have its toll on the coat of epoxy over time as they may become brittle and break under the shock of extreme temperature fluctuations.
So, while epoxies have some heat resistance and can survive some degree of thermal fluctuations, their resistance is only approximately half that of polyurethane systems.
For this reason, you may want to go for polyurethane if the project will be subjected to extreme temperature changes on a regular basis.
The product will inherently be able to handle the heat better and give a longer service life in such conditions than epoxy coatings.
Polyurethane versus epoxy resin: Sheen level
Epoxy resin generally creates dull surfaces and must usually be polished to increase its shine. This means if you want a glossy floor coating with epoxy, you must be prepared to do some extra work to achieve that sheen level.
The epoxy coating is inherently dull, so it is best to use it in areas where matte finishes are preferred. Creating a high gloss sheen with epoxy surfaces may require both equipment and an added step in the finishing process.
Polyurethane comes in a wide range of sheen levels. You can choose a high gloss option to achieve a shiny finish without any polishing added to the process.
People who prefer satin or matte finishes can go for polyurethane formulations with these sheen levels specified on the label already.
So you can effortlessly achieve any sheen level you want with polyurethane coating than epoxy, as the latte requires added work to customize the sheen.
What is the difference between PU and epoxy?
Even though polyurethane and epoxy are both resins, their respective molecules differ in structure and therefore fuse together differently while curing. Epoxy polymers tend to have lower cross-link density compared to polyurethanes. Epoxy polymers are generally less durable than polyurethanes due to this difference in molecular structure.
Is epoxy or polyurethane better for wood?
Even though polyurethanes are less tough than epoxies, they generally offer better durability for surfaces like wood, making them the better choice between the two resins. Polys are more durable and long-lasting than any wax available. Additionally, polyurethanes offer the best aesthetic versatility for floor coatings, with options ranging from amber to crystal clear finishes across oil-based and water-based formulations. You can also have your polyurethane finish in matte, satin, semi-gloss, or high-gloss sheen. A popular argument regarding polyurethane is that high-luster sheens tend to be more durable, so you may consider this while choosing your finish.
Is polyurethane better than epoxy for a garage floor?
Both polyurethane and epoxy are ideal for different roles in garage floors. Due to their toughness and high-adhesion quality, epoxies make excellent base coats and primers for garage floors. On the other hand, the inherent chemical and abrasion resistance of polyurethanes make them ideal for topcoats. Therefore, when coating a garage floor, it is best to use both epoxy and polyurethane as a base coat and topcoat, respectively, to create a formidable combination and lasting protection for your garage floor.
Is epoxy and urethane the same thing?
Both epoxy and polyurethane are polymers, but they are not exactly the same thing. Both the epoxy and polyurethane polymers consist of large molecules with a repeating structure all over their bodies, but that is as far as their similarity goes. Polyurethane is composed of organic or carbon links that react with a monomer in the structure, while the epoxy is a two-part substance consisting of an epoxide or polyamine resin and hardener. When these two parts come together, they chemically react to form a hard material: epoxy.
Whether you have a commercial or residential property, polyurethane and epoxy can be perfect finishes for your project.
When used correctly, either product can add unmatched utility to hardwood floors, concrete flooring, countertops, and several other wooden surfaces.
There is no one-size-fits-all answer regarding which product is best between polyurethane and epoxy. The ideal choice will depend on the project, its utility, and the conditions around it.
If you have a difficult time choosing between the two, feel free to refer to this detailed guide and use epoxy, where its pros outweigh the cons.
On the other hand, use polyurethane in cases where its strengths are more aligned with your project than its limitations.