The subject of a polyurethane or epoxy coating for a garage floor eventually comes up when deciding on what materials to use for your project. Admittedly, it can become a bit confusing when asking around or researching which floor coating is best to use. Epoxy and polyurethane are great for protecting your floor against stains, damage, chemicals, oils, and wear. They are both light reflective, easy to clean, and long lasting. They also have their own advantages depending on the application. So which one should you use and what is the difference? Well, the short answer for most applications is to use both. Let’s see why.
Epoxy Floor Coating Benefits
Epoxy is a thermosetting polymer which is available in three different formulations for a garage floor coating and sealer; water based, solvent based, and 100% solids. These formulations allow for varying degrees of thickness from 3 mils to over 10 mils for a single coating for a garage floor. They also allow for ease of application, special bonding characteristics, and VOC considerations. Epoxy bonds extremely well to properly prepared concrete and can sometimes be used as a resurfacing agent for old or worn concrete that need a new garage floor surface.
The best epoxy formulations are 100% solids and provide for an extremely hard, thick, and impact resistant surface. This self-leveling thickness contributes to filling in the small hairline cracks and imperfections of the floor as well as providing protection. It also works well against hot tire pick up, scratching, and wear from abrasion. Though some epoxy formulas come with U.V. inhibitors, they will still eventually yellow or amber as the industry calls it when exposed to sunlight for any length of time.
Polyurethane Floor Coating Benefits
Like epoxy, polyurethane is a thermosetting polymer as well and is considered a high performance coating. It is commonly known as urethane for short, though that it is technically incorrect and there is actually a big difference between polyurethane and urethane. If someone is advertising a urethane coating, it is actually polyurethane.
Of the different formulations available, aliphatic polyurethane is the desired choice for garage floors. Though they are approximately 60% to 70% solids depending on the manufacturer, a polyurethane coating is only about 2 to 3 mils in thickness and can’t be adjusted as with epoxy.
Don’t let the thinner dry film thickness fool you however. Aliphatic polyurethane has more flexibility than epoxy and it is this flexibility that aids in absorbing impacts better. It is also much more abrasion resistant, in fact, some manufacturer’s claim that the wear resistance of polyurethane over epoxy is almost 3 to 1. The resistance to chemicals is better than epoxy as well and this includes resistance to solvents such as methylene chloride which is the primary ingredient in paint stripper.
Another advantage of polyurethane over epoxy is that it is U.V. stable. This means that it won’t yellow like epoxy does when exposed to small amounts of sunlight. The surface of polyurethane is not as hard as epoxy but it is much more scratch resistant, can tolerate larger temperature swings and handles humidity much better. It is also available in different finishes from satin to very glossy.
Though polyurethane has many advantages over epoxy, it does not bond well to concrete and its thin dry film thickness will not work well as a self-leveling coating to fill in small cracks and divots in the surface. Another consideration is that most polyurethanes are solvent based, they can have high VOC’s and may require a respirator to apply.
So, which should you use? As a rule, it is believed that you will get maximum performance by using both polyurethane and epoxy together for your garage floor coating. Epoxy is best used for building up the thickness of your floor coating then following up with polyurethane as a clear coat to protect it. It will help protect the epoxy from yellowing and it will provide for a longer wearing and more scratch resistant surface. If you don’t want to worry about yellowing at all, you can always use a colored polyurethane as a final color coat before the clear coat. Polyurethane is also a better medium than epoxy to mix in anti-slip aggregate if you truly want an anti-slip surface or want a solid colored floor without paint chips.
Something else to consider is that most epoxy clear coats are not actually crystal clear like polyurethane is. Though they have no color, there is a slight yellowish brown tint to the clear in epoxy. Unless you opt for a more satin finish, polyurethane can provide a very glossy surface that gives your floor depth.
So unless you are just doing a one-coat epoxy coating for your garage, a combination of epoxy and polyurethane is almost always the best answer to get the maximum combined benefit out of both materials. The result is a high performance garage coating that will stand up to the rigors of a working garage for years to come.