Whether you have outdoor wood furniture purchased from a store or you built your own wooden piece, finding a clear-coat protective finish is extremely important. The reason you never want to skip using a clear finish for outdoor wood furniture is that when the wood is not properly sealed outside it can become seriously damaged from the weather, both water, and UV damages.
The best clear coat finish for outdoor wood furniture is spar urethane because it creates a durable waterproof surface and UV resistant barrier that helps prevent the wood from rotting.
Application is super easy too, simply apply using a brush and make sure you brush it over every inch. You want to make sure nothing is exposed or it has a higher chance of rotting, water can get into any sized crack so lathering it on in multiple coats will reduce the chances of missing unprotected wood.
What is Spar Urethane?
Spar Urethane is a clear coat finish used on interior and exterior wood projects as a form of protection. It is a popular choice for outdoor wood because of its strong outdoor protection characteristics. Spar urethane provides great protection against rain and moisture, the special formula produces a thick and durable surface that prevents water from touching and entering into the wood. It’s almost like a hard rubber or plastic layer saving your wood from water damage.
It also carries UV-blocking ingredients that protect outdoor wood furniture from sun damage known to fade and lighten wood to look grey in color. It also has “special oils” which adapt to the temperature changes throughout the year.
Spar urethane can be used on so much more than just outdoor furniture, it has been a popular choice for exterior doors and windows, outdoor countertops, and many indoor projects too. In my opinion, I would choose some other product on inside surfaces, like on my furniture projects inside I choose lacquer or polyurethane. Spar urethane would be overkill inside.
How Many Coats of Spar Urethane for Outdoor Furniture?
When applying spar urethane on outdoor furniture apply a minimum of 3 coats using a natural bristle brush. Without 3 coats you risk not fully protecting the wood from such natural damages, which could lead to fading colors and rotting wood. It is recommended from wood finishing experts that if you apply 6-8 thin coats you will get the most durable finish. The most I ever applied was 6 coats, but I think that is almost overkill. Apply 4 coats and re-apply one coat per year for ultimate protection.
Do You Have to Sand Between Coats of Spar Urethane?
It is recommended to sand between coats of spar urethane, just like other products sanding before applying helps the next application adhere better to the current surface. Use a 220 grit sanding sponge and do a light scuff on the surface before re-coating. There is no need to sand the final surface of spar urethane.
Spar urethane is known to bubble when applied in thick heavy layers, you can sand these bubbles out between coats for an ultimately smooth finish. When I apply this stuff on exterior surfaces I sometimes skip sanding all together, it still holds strong and lasts a long time. I have a wooden chair I built for outside using 2×4 and pallets, it is holding strong with the spar urethane I used after it has been through multiple storms and also a Canadian winter.
Best Spar Urethane for Outdoor Furniture?
My favorite spar urethane to use on outdoor furniture is Helmsman Spar Urethane by Minwax in a clear satin finish. I used it on a couple of exterior sofas now and had nothing but great results. I applied it to untreated wood and it completely sealed the wood from water and UV damages.
The finish is very clear, but if you are applying it on a light color wood it can give it a slight yellow tint, although it says crystal clear I don’t think that’s truly the case. I spilled some on the garage floor and I peeled it up later and you can see the color is slightly yellowed, but really its hard to notice when on a piece of furniture.
Example of Spar Urethane on Outdoor Furniture
Take a look at my outdoor sofa that has spar urethane applied all over it!
I applied a wood stain first on the untreated wood to give it a professional look. Then I applied 4 coats of spar urethane and it has been very durable against the crazy weather I have been having. If it can protect untreated wood for outdoor use it will definitely keep treated wood safe without a doubt.
Other Popular Outdoor Wood Finishes?
Spar urethane isn’t the only outdoor wood finish that you can choose. I do recommend it because it is so easy to use. It can last year after year, I think applying once a year is a good practice but it’s not truthfully required. Spar urethane is great because it can last 2-3 years without needing a touch-up. Anyways, let’s look at some other exterior wood finishes for outdoor furniture.
Exterior Oil Finish
Exterior oil is known to be a simple and fast exterior finish to apply over outdoor furniture. It works differently than spar urethane and other exterior varnishes. Exterior oil finish penetrates inside the wood and dries out, this creates protection against UV rays and also against mold plus mildew rotting.
There are different types of oils, some are natural wood oils and others are full-on chemically formulated oil finished for ultimate protection. Natural wood oils are not as strong for exterior use and require a lot of maintenance to keep the color.
Penofin Oil Finish
Penofin penetrating oil finish is a very powerful oil finish that can be applied in one coat by letting it soak into the wood. This formula creates a weather-resistant barrier that prevents water from damaging the wood, mildew growth, and other moldy encounters. This oil is made to keep the wood looking natural for many years if following the instructions correctly. If looking to protect an expensive piece of wood without covering it with a varnish use this oil. I don’t use it because it is rather expensive.
Natural Oil Sealer/Finish
The most popular exterior natural wood oil is teak oil, which can be used on many other types of wood, not only teak. If using it on teak the Star Brite Premium Teak Care Kit is your best bet. It really brings faded wood back to life! There is also tung oil too, but the thing about using oil finishes for outdoor furniture is the number of coats you need to apply. These oils need to penetrate and get inside the wood for ultimate protection, making it important to apply enough or you will have natural damages. This can be time-consuming and difficult to judge.
Oils can be rubbed on using an old rag or you can apply using a small spray bottle, garden sprayer, or some other spraying alternative. You are likely not going to get a crystal clear finish using oil. Typically oils enhance the natural colors of wood making them brighter than before, almost in a healthy-looking way.
I do like epoxy and I know how weatherproof it can be, but it’s just a time-consuming process that can be intimidating for beginners. It’s best when mixed with an exterior varnish. Epoxy doesn’t protect the wood from UV damages like other finishes, so apply an exterior varnish such as spar urethane underneath and you’ll have that protection from graying and fading. Epoxy is great for waterproofing, it can be applied over a wood surface while being 1 inch thick if you wanted. It is the most durable and heavy-duty finish for outdoor wood surfaces, that’s for sure. I think it works best for restaurant tables that need that extra level of durability.
But think about it, the process is a lot of work for outdoor furniture pieces. A piece of furniture with many angles and corners would take hours to properly finish. You need to heat the bubbles out before they dry underneath, this requires proper tools such as a mini torch. Furthermore, you need to make sure no dust gets on the wet surface. After applying the epoxy resin you then need to let the surface dry at correct temperatures for about 72 hours, which is a timely process. Epoxy is also expensive compared to other methods on this list, but it does provide the most durability for your outdoor surface, at your time and monies expense.
The best time to use epoxy resin on outdoor furniture is on tabletop surfaces. This gives a thick durable surface that will last for many long years outside. Using Clear Table Top Epoxy mix would be your best option for affordable and high-quality epoxy for outdoor use.
Other Exterior Varnishes
Spar urethane is an exterior varnish and isn’t the only option out there. Many exterior varnishes exist and here are some other options you can use on your outdoor wood furniture projects:
- Rust-Oleum Marine Spar Varnish
- RUST-OLEUM Outdoor Clear Gloss Spar Urethane Finish
- General Finishes Exterior 450 Water Based Topcoat
- System Three Clear Marine Spar Urethane Varnish
So, what is the best clear finish for outdoor wood furniture? Outdoor protection is very difficult and it’s almost inevitable to use an exterior finish without ever needing to re-apply over a period of time. Using epoxy would likely be your best bet for longevity, but also the most difficult to apply and go through the process. Using an exterior varnish such as spar urethane is your best bet for simple use and effectiveness. I recommend exterior varnishes for simple outdoor projects that are built yourslef or just need that extra weatherproofing. If you want to restore some colour apply some oil to bring it back to life!
Appling whatever option you choose at least once a year is recommended, it will help your exterior furniture last for many years down the road.