How Long Does Spar Urethane Last Outside? Durability & Protection Tips

Spar Urethane offers a formidable shield, safeguarding wood from moisture, sunlight, and fluctuating temperatures.

Known for its robust composition, this wood finish combines resins and oils, fortified with UV blockers, to extend the life of your outdoor furniture and decks.


Spar Urethane typically lasts 2-5 years outdoors, with longevity depending on maintenance and climate conditions.

Spar Urethane’s Durability

Wooden Deck With Furniture

Spar Urethane, renowned for its exceptional durability, offers two main types: oil-based and water-based; each providing unique benefits for outdoor wood protection.

Oil-Based Spar Urethane

  • Durability: Creates a thick, protective layer that is highly resistant to water and wear.
  • UV Protection: Contains UV blockers for superior resistance to sun damage.
  • Longevity: Tends to last longer, often exceeding the minimum expected lifespan outdoors.

Water-Based Spar Urethane

  • Ease of Use: Easier to apply with faster drying times and low odor.
  • Aesthetic: Less prone to yellowing, maintaining a clear finish.
  • UV Resistance: Modern formulas include UV absorbers, though may require more frequent reapplication.

For outdoor furniture, a minimum of 4 coats of Spar Urethane are recommended to ensure maximum durability and protection.

UV Protection and Longevity

The longevity of Spar Urethane is significantly influenced by its ability to block harmful UV rays:

  • UV Blockers: Both oil-based and water-based Spar Urethane contain additives that absorb UV light, protecting the wood from fading and degradation.
  • Maintenance: To maintain UV protection, reapplication is recommended every 2-3 years, depending on exposure.

Oil-Based Vs. Water-Based Spar Urethane Comparison Chart

FeatureOil-Based Spar UrethaneWater-Based Spar Urethane
UV ResistanceExcellent UV protectionGood UV protection
Weather ResistanceSuperior resistance to weatherGood resistance to weather
ApplicationMore complex, longer dryingEasier, faster drying
OdorStronger odorLow odor
Environmental ImpactHigher VOCsLower VOCs
FinishRicher, may amber over timeClearer, less prone to yellowing
Maintenance FrequencyLess frequent reapplicationMore frequent reapplication
Expected Longevity OutdoorsTypically 3-5 years or moreTypically 2-4 years

Factors Influencing Outdoor Longevity

The longevity of Spar Urethane outdoors is influenced by a variety of factors beyond its type, all of which collectively contribute to the finish’s endurance.

Climate Impact

  • Extreme Weather: Areas with intense sun, heavy rain, or snow can accelerate the breakdown of Spar Urethane.
  • Temperature Fluctuations: Frequent changes in temperature can cause the wood to expand and contract, stressing the finish.

Maintenance Requirements

  • Regular Reapplication: Preserving the integrity of Spar Urethane involves reapplying the finish every few years.
  • Routine Cleaning: Keeping the wood clean from dirt and mildew helps prevent the finish from deteriorating.

Wood Type and Pre-treatment Effects

  • Wood Density: Hardwoods with dense grains withstand outdoor conditions better when coated with Spar Urethane.
  • Proper Pre-treatment: Sanding, sealing, and priming the wood can enhance the finish’s adhesion and effectiveness.

Maximizing the Life of Your Spar Urethane Finish

To ensure your Spar Urethane finish remains effective and aesthetically pleasing over time, adhere to these maintenance strategies:

Maintenance Tips

  • Shield from the Elements: Whenever possible, position woodwork to minimize direct exposure to weather.
  • Prompt Repairs: Address any chips or cracks immediately to prevent moisture ingress and further damage.

Reapplication Frequency

  • Assess Annually: Check the finish each year and plan to reapply a coat of Spar Urethane every 2-3 years or more frequently if the wood is in a harsh climate.

Regular Cleaning and Inspection

  • Gentle Cleaning: Use a soft brush and mild detergent to clean the surface without damaging the finish.
  • Thorough Inspection: Look for signs of wear, such as dulling or loss of sheen, which indicate it’s time for maintenance.

Spar Varnish vs. Spar Urethane

Spar Varnish offers deep wood penetration and a classic, transparent look but tends to yellow over time, while Spar Urethane provides a durable, less yellowing finish with quicker drying times.

The choice between the two depends on the desired finish: ‘Satin’ and ‘Semi-Gloss’ Spar Urethane preserves more color, whereas ‘Gloss’ and Spar Varnish offer greater transparency.

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Last update on 2024-06-14 / Affiliate links / Images from Amazon Product Advertising API