Spar Urethane On Cedar (Ultimate Guide!)

Ever marveled at cedar’s charm? Can Spar Urethane magnify its magic? Read on!

spar urethane on cedar

Spar urethane is known as a type of spar varnish. It is mainly used to seal and protect outdoor furniture and woodwork from weather elements.

I have worked with spar urethane to finish several of my cedar patio furniture, desks, and cabinets and all went pretty well with an excellent protective finish.

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    Here’s what I know about using spar urethane on cedar.

    So, let’s discuss, Can you use Spar urethane on Cedar?

    Yes, you can use spar urethane on cedar with no issues. Spar urethane hardens to a protective finish over cedar with excellent weather resistance and UV resistance. Spar urethane seals and makes cedar waterproof. Spar urethane can spray, brush or wipe on cedar and it comes in several sheens.

    But there’s a lot more you need to know about using spar urethane on cedar.

    In this article, I’ll dig into is spar urethane good for cedar, how to apply spar urethane properly on cedar wood furniture, the benefits of spar urethane, and lots of tips and techniques.

    Furthermore, I’ll answer some frequently asked questions as well.

    Let’s dive in!

    cedar furniture and woodworks finished with spar urethane

    Is Spar Urethane Good For Cedar?

    Spar urethane is one of the best finishes for cedar especially when it comes to sealing outdoor furniture of cedar.

    Spar urethane cures and hardens to a super protective coat over cedar that can tolerate extreme weather conditions such as rain, snow, direct sunlight, high-temperature levels, and high humidity levels.

    Cedar wood takes spar urethane perfectly to get a nice, even-looking finish.

    spar urethane protects wood from sunlight

    Spar urethane comes in several sheens including gloss, semi-gloss, and satin. That depends on the amount of reflectivity of its coating.

    Spar urethane is thicker and harder than a regular polyurethane finish. Therefore, you can apply urethane on cedar with a less number of coats.

    Two main types of spar urethane can use on cedar,

    1. Oil-based spar urethane
    2. Water-based spar urethane

    Here’s how oil-based spar urethane differs from water-based one when applied to cedar wood,

    Oil-Based Spar Urethane On CedarWater-Based Spar Urethane On Cedar
    Less expensiveExpensive
    Darkens the wood over timeProvide a natural clear finish
    Makes a thick coatingMakes thin coating
    Susceptible to dentsSusceptible to scratches
    Takes more time to cureTakes less time to cure
    Need less number of coatsNeeds a higher number of coats
    Produce amber/yellow toneNatural clear tone
    Difficult to clean and require mineral spiritsEasy to clean with water

    Ultimately both water-based urethane and oil-based urethane works well on cedar wood and makes a protective coat with excellent protection from weather elements.

    Cedar table finished with spar urethane
    Cedar table finished with spar urethane

    Once you apply spar urethane on cedar, its chemical ingredients will start to react with atmospheric oxygen and polymerize into a hard protective layer.

    Moisture, insects, and sunlight are unable to travel through this spar urethane protective layer. It helps to protect cedar wood underneath from moisture damage and rotting.

    Since there’s no way for outside elements to get inside the cedar wood, the wood gets isolated. As a result that the durability of cedar wood will increase with a spar urethane finish and protection from weather elements.

    Plus, spar urethane enhances the cedar wood’s appearance by highlighting the wood grain and providing an extra sheen to the wood.

    It gives a fresh appearance to your cedar wood furniture and woodwork.

    benefits of spar urethane

    Spar urethanes contain UV blockers that help to protect cedar wood from direct sunlight.

    Direct sunlight contains harmful UV rays that damage the wood by making wood cracks and causing wood discolorations.

    UV blockers in spar urethane finish block UV rays and protect the cedar wood. therefore, you don’t need to worry about placing cedar wood placing under direct sunlight after finishing with spar urethane.

    Overall, spar urethane is an excellent finish for cedar with multi-function features. You can use it for any cedar wood furniture or woodwork with no issues. Just follow the correct procedure.

    Spar Urethane Applications Of Cedar Wood

    You can apply spar urethane on the following cedar wood furniture and woodwork,

    • Cedar wood patio furniture
    • Cabinets
    • Cedar wood carving projects
    • Exterior columns
    • Fences
    • Cedar wood interior furniture
    • Flooring

    As you can see, spar urethane is able applied literally for any cedar wood project.

    best finishes for cedar

    Let’s have a look at the more summarized view of the benefits of spar urethane on cedar.

    Benefits Of Using Spar Urethane On Cedar

    • Spar urethane makes cedar wood waterproof
    • Spar urethane finish cedar wood from extreme weather condition (rain, snow, temperature changes)
    • Enhance the wood appearance by highlighting the wood grain
    • Spar urethane blocks UV rays in sunlight and avoid cedar wood from fading
    • Protects wood from insects and bugs attacks
    • Easy to apply with few coats
    • Improves the wood sheen
    • Fix cedar wood cracks and small gaps
    • Spar urethane is food safe when it is cured
    • Non-toxic
    • Spar urethane increases the durability of cedar

    As you can see urethane is filled with lots of benefits.

    Spar urethane products

    So, let’s head into the most interesting part which means the application process of urethane on cedar.

    Tools And Materials To Apply Spar Urethane On Cedar

    • Spar urethane (water-based or oil-based)
    • Mineral spirits for oil-based spar urethane or denatured alcohol for water-based spar urethane
    • Lint-free tack cloth
    • Clean rags
    • Bristle brush /paintbrush/sprayer
    • 120 grit sandpaper
    • 320 grit or 400 grit or finer sandpaper
    • Face mask
    • Latex gloves
    • Cedar furniture or woodwork
    • Cedar scarp wood piece (optional)
    how to apply spar urethane on cedar

    How To Use Spar Urethane On Cedar?

    1. Surface preparation and cleaning
    2. Sanding the wood surface
    3. Thin spar urethane with mineral spirits or denatured alcohol
    4. Apply the first coat of spar urethane on the cedar
    5. Let it dry properly
    6. Light sanding the coat
    7. Apply more spar urethane coats
    8. Let the coats dry and cure

    Let’s discuss, each of the above steps in detail to have a clear view of the application process of spar urethane on cedar.

    1. Surface Preparation And Cleaning

    Before starting the finishing process, take the cedar wood furniture or woodwork to a well-ventilated area or open the windows in your working area.

    Having proper air circulation helps spar urethane coats to dry fast and efficiently.

    Plus, proper ventilation helps to remove harsh chemicals and fumes that release when applying spar urethane on the wood surface.

    Therefore, do the finishing process in an open space with good ventilation. Wear a mask and gloves to avoid spar urethane from contacting eyes and skin which can cause irritations.

    Ventilated area for finishing cedarwood with spar urethane

    Then, clean the entire cedar wood surface with clean rags to remove dust, dirt, grease, and debris.

    Cleaning is a must because dust and dirt can easily get trapped inside the urethane coat and cause many troubles reducing the performance of finishing coats and ruining the wood’s appearance.

    Use TSP (trisodium phosphate) to remove stubborn dirt from the cedar wood surface. Let the wood dry after cleaning.

    Now cedar wood furniture surface is super nice and clean.

    2. Sanding the Wood Surface

    Now sand the entire wood surface with 80-grit or 120-grit sandpaper to remove surface randomness, bumps, and drips.

    Sand along the direction of the cedar wood grain with even pressure to avoid making sanding marks and scratches on the surface.

    Sanding helps to open the small porous structures of cedar wood which helps to absorb spar urethane better into the wood for an even finish.

    Sanding cedarwood before finishing

    Sanding helps spar urethane to stick better onto the cedar wood surface.

    Sand the entire surface without missing any spots.

    Once you’re done with sanding, clean the entire surface with clean rags or use a dust collection pipe system to collect and remove sawdust.

    Never leave sawdust or other residues on the surface upon finishing since they interrupt the finishing coat.

    3. Thin Spar Urethane With Mineral Spirits or Denatured Alcohol

    Thinning is an optional step that helps to get an even, smooth, and smooth thin coat of spar urethane on cedar wood.

    Thinning makes the application process lot easier, especially because spar urethane makes a thick coat over cedar wood which takes forever to dry.

    Thinning makes the absorption process easier and helps coats to dry faster without forming a tacky or splotchy surface.


    • You can apply spar urethane by brushing, spraying, or wiping on it.
    • If you wish to apply spar urethane on cedar with a sprayer thinning is not necessary since the spray releases spar urethane as thin as possible.

    If you’re willing to apply spar urethane by brushing or wiping on, this thinning step helps you more.

    Oil-based spar urethane can be thinned by mixing with mineral spirits and water-based spar urethane can be thinned by mixing with denatured alcohol.

    Thinned  oil-based spar urethane with mineral spirit

    Mineral spirits and denatured alcohol have a high evaporation rate when they are exposed to the outside air.

    Mixing oil-based spar urethane with mineral spirits increases the evaporation rate of the solution and thinned spar urethane will also dry faster because of the quick evaporation.

    Same as when water-based spar urethane mix with denatured alcohol

    • To thin oil-based spar urethane mix four parts of spar urethane with one part of mineral spirits in a mixing container.
    • To thin water-based spar urethane mix four parts of spar urethane with one part of denatured alcohol in a mixing container.

    The mixing container can be a glass jar or plastic measuring cup.

    After mixing, your thinned spar urethane mixture is ready to seal the cedar wood even better.

    4. Apply The First Coats Of Spar Urethane On Cedar

     Now it’s time to apply the first coat of urethane on cedar wood. You can apply spar urethane on cedar by brushing, spraying, or wiping on.

    Select your preferred application method.

    Apply a thin coat of spar urethane all over the cedar wood along the direction of the wood grain.


     Better if you can test how to spar urethane behaves with cedar wood by applying it on the scarp wood piece first. Testing spar urethane on scarp wood help to minimize your mistakes and to see how the final outcome will be.

    When you’re brushing spar urethane, brush with even strokes and catch runs.

    Applying spar urethane on cedar

    Applying along the wood grain helps spar urethane to penetrate deep into the wood by forming an even finish with no random blotches.

    Apply spar urethane on cedar with even pressure to get an even color all over the wood and make sure not to miss any spots during the application process.

    When you apply the first coat of spar urethane on cedar, you’ll notice it will quickly absorb into the wood. That’s because cedar loves to take spar urethane.

    When you keep applying the top layer of cedar wood fibers will be saturated with spar urethane and the excess will sit and settle on the cedar wood surface.

    After applying the first coat of spar urethane, let it sit and settle on the cedar for about 30 minutes and wipe the excess using a clean rag.

    cedar floor finished with spar urethane

    Removing the excess spar urethane on the surface is essential to make the spar urethane coat dry faster and help to get an even finish all over the surface.


    • Don’t let spar urethane can shake during the application process since bubbles can trap inside the spar urethane causing bumps on the finished cedar wood surface.
    • Use a quality bristle brush to apply spar urethane since exploded synthetic brushes contain air which may release air bubbles to the finished surface

    5. Let the Spar Urethane Coat Dry Properly

    After applying the first coat of spar urethane on cedar let it dry for 24 hours. But sometimes can even take days due to the thickness of your spar urethane coat.

    Thin spar urethane coats dry faster than thick ones.

    Generally, oil-based spar urethane takes more time to dry than water-based spar urethane. Drying time can vary on the environmental humidity and the temperature levels outside.

    Letting spar urethane dry properly

    During the drying time, spar urethane settled on the cedar wood surface making a protective coat that helps to protect the wood from weather elements.

    Upon drying you’ll be able to see the mistakes you have made during the application of the first spar urethane coat. Try to fix them by reapplying and minimal mistakes can be fixed when applying more coats.

    Check the dryness of the surface before moving to the next step.

    6. Light Sand The Spar Urethane Coat

    When the first coat of spar urethane dries completely, lightly sand the entire coat with 320-grit or 400-grit sandpaper along the direction of the wood grain.

    Make sure to do light sanding with even pressure without damaging the spar urethane coat.

    Sanding helps to smoothen the surface and build a good adhesion between the spar urethane coats.

    Sanding basically gives the adhesive properties to the existing spar urethane coat. That helps the next spar urethane coat to stick better to the previous coat.

    Light sanding the spar urethane coat

    Light sanding between coats prevents layer separation and gives you a nice, smooth, and thin finishing coat.

    Once you’re done with sanding, clean the entire surface with clean rags to remove residue and dust before stepping into the application of the second coat.

    7. Apply More Spar Urethane Coats

    Now apply the second coat of spar urethane above the previous coat on cedar wood along the wood grain without leaving brush marks on the surface.

    Follow the same application procedure which you used when applying the first coat when applying the second.

    Likewise, apply at least 3 coats of spar urethane on cedar wood to get a super protective finish with a nice and even finish.

    You can go up to a maximum of 5 coats of spar urethane on cedar, but make sure to apply thin, even coats and let each coat dry well for at least 24 hours before applying another.

    Apply spar urethane coats on cedar

    After three coats your cedar wood will be fully protected from extreme weather conditions, and you’ll be able to notice the beautiful sheen on the wood.

    Spar urethane just not only protects your cedar wood furniture from outdoor elements but also enhances the wood’s appearance.

    It waterproofs the wood to protect cedar wood from water damage, moisture damage, and rotting.

    8. Let The Coats Dry And Cure

    After applying the final coat of spar urethane, let it dry for 24 hours and cure for 2 to 3 days.

    Yes, curing takes time, especially when the spar urethane is oil-based.

    Upon curing spar urethane finishing coat will reach its final appearance by making a super hard protective coat that works as a barrier between the outside and the wood underneath.

    You don’t need to lightly sand the final coat of spar urethane since we won’t apply another one on top of it. Let it be as it is.

    Final spar urethane coat curing for days

    Never apply any spar urethane coat before the existing one dries completely. Applying spar urethane over a wet surface can ruin the wood’s appearance and won’t give the protection to the wood you want.

    After 3 days, check the status of the cedar wood and use it only when you feel the surface is completely dried. Otherwise, leave it there for another 2 days to cure completely.

    That’s it, mate. Now you know how to apply spar urethane on cedar properly using the correct method without making any mistakes. Try this out!

    How Long Does Spar Urethane Last Outside?

    Spar urethane finish lasts for approximately about 2 to 3 years. With proper cleaning and maintenance spar urethane coats may last even over a decade.

    Apply spar urethane at least once per two years to keep the wood protected forever from weather elements, moisture, sunlight, UV light, and water damage.

    Plus, applying spar urethane at least once per two years helps to keep the wood sheen and freshness continuously without losing the natural beauty of the wood.

    Differences between Oil-based & Water-based Spar Urethane

    If your furniture gets amber-toned or darkened over time after applying spar urethane, you can get its original color again by applying a new spar urethane coat by removing the old layer.

    Normally, spar urethane lasts outside for about 5 years after opening the container. Make sure to keep the spar urethane can in a dry, dust-free environment.

    Otherwise, it will turn bad pretty quickly and you’ll have to buy a new one when restoring the wood furniture after a few years.

    What Is The Best Finish For Cedar Wood?

    Here’re some of the best finishes for cedar wood,

    All the above finishes work well on cedar wood by making a protective coat to protect the wood from environmental elements and enhance its natural appearance of cedar wood.

    spar urethane coats on cedar

    Spar varnish and spar urethane are the best finish for cedar wood exterior furniture and woodwork since they make a tougher protective coat than other finishes.

    That coat is specialized to tolerate extreme weather conditions by isolating and protecting the wood inside for a long time.

    What Kind Of Spar Urethane Do You Use On Cedar?

    Here are some of the popular abe best-performing spar urethane products for cedar,

    • Helsman Spar Urethane
    • Water Based Helsman Spar Urethane
    • Ultimate Spar Urethane – Varathane
    • Spar Urethane – Olymic Stains
    • BEHR Oil-Based Spar Urethane

    How To Protect Cedar Wood For Outdoors?

    To protect cedar wood outdoors, apply a waterproofing sealer such as polyurethane, spar urethane, varnish, or tung oil on cedar wood to make a protective coat and protect it from weather elements.

    Applying a quality finisher over cedar helps to protect the wood from moisture damage, humidity, insect attacks, UV light, and rotting the wood.

    Seal cedar wood with thin coats of finishers evenly all over the wood and let each coat dry properly until it hardens on the cedar wood surface before placing outside.

    spar urethane protects cedar wood from moisture

    Use quality, branded, fresh finishes to deal with cedar wood. Reapply the finish at least once per two years to keep the protection continuously without letting the wood gets damaged by outdoor elements.

    How Do You Weatherproof Cedar Wood?

    You can weatherproof cedar wood by applying 3 coats of spar urethane finish after mixing and thinning each with mineral spirits or denatured alcohol.

    Let each coat dry properly at least for 24 hours and let the final coat dry and cure for 2 to 3 days.

    Light sand between each coat to make thin coats and stick every coat well onto the cedar wood surface.

    When spar urethane reacts with the outside air, it will polymerize into a protective coating which makes cedar wood weatherproof and tolerate extreme weather conditions like rain, snow, and extreme temperature levels.

    Cedar stair floor finished with spar urethane

    What Is The Best Exterior Oil For Cedar?

    Here’re the best exterior oils for cedar wood,

    • Danish oil
    • Linseed oil
    • Tung oil
    • Teak oil

    Let’s answer some frequently asked questions.


    Why should I consider using Spar Urethane on cedar?

    Cedar, although naturally resilient, benefits from Spar Urethane’s added protection, enhancing its lifespan and preserving its natural beauty.

    Can I apply Spar Urethane over stained cedar?

    Absolutely! Just ensure the stain is fully dried before applying the urethane to avoid any unwanted reactions.

    How many coats of Spar Urethane should I apply on cedar?

    Typically, 2-3 coats provide optimal protection. Allow each coat to dry thoroughly before applying the next.

    Does Spar Urethane yellow over time?

    All clear finishes can yellow with age, but high-quality Spar Urethane is formulated to resist yellowing, especially when exposed to UV light.

    How long does Spar Urethane last on cedar?

    With proper application and under normal conditions, it can last several years. Its lifespan may vary based on environmental factors and wear.

    Is it safe to use indoors?

    While Spar Urethane is excellent for outdoor projects, it can be used indoors. Ensure good ventilation during application and drying.

    Did I cover all you wanted to know about: Using Spar Urethane On Cedar

    In this article, I have deeply discussed, whether can you use spar urethane on cedar and how to apply spar urethane on cedar properly using the correct steps without messing things up. Plus, we have discussed important tips to make things easier for you.

    Spar urethane works perfectly on cedar by making a protective coat to protect cedar from moisture, UV rays, insect attacks, cracks, and dents. Plus, it enhances the cedar wood’s appearance by highlighting the natural grain of the wood. apply thin coats of spar urethane on cedar and light sand between each for a nice and even finish.

    Furthermore, I’ve answered some frequently asked questions as well.

    Hope you learned everything you wanted to know about applying spar urethane on cedar using the right methods.

    Try to finish your cedar wood furniture and woodwork with spar urethane and experience the difference between spar urethane over other finishes.

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    Walter Parker is a woodworking enthusiast. He is passionate about woodworking projects & plays with woodworking tools having spent over 2 decades as a leader for Woodworking Planet. He wants to make people love woodworking! Read More About Him! Follow him on Twitter, Facebook and Linkedin.

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