The Best Deck Sealers for Protection Against the Elements

Protect your deck from damage caused by sunlight, moisture, and mold with the best deck sealer.

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Best Deck Sealer - Rain Protection

Photo: depositphotos.com

A deck functions as the living room of an outdoor space. For many people, the deck is where they make memories: relaxing, laughing, socializing, enjoying. It’s the perfect spot for a warm-weather batch of barbecued burgers, an enjoyable evening spent with a glass of wine and a favorite person, or a fun-filled family get-together.

As with all things made of wood, a wood deck is subject to deterioration from exposure to the elements. Sun, rain, snow, and wind all take their toll, wearing away at the wood and leading to cracks, splinters, fading, and rot. That’s why it’s so important to protect decking from weather conditions with regular applications of sealer.

The best deck sealer protects from damage due to rot and unsightly mold or mildew while still allowing the wood’s natural grain and color to show. This is the reason many people prefer a deck sealer that penetrates the wood rather than a deck paint that only sits on top of it.

For those who don’t want to alter the deck’s original look, sealer is also a better option than deck stain, which changes the color of the natural wood. Sealing a deck is also an easier task for the average DIYer—clear deck sealer won’t so easily reveal an uneven application, brushstrokes, or errant drops, unlike colored stain or solid paint.

Read on to learn more about the considerations to keep in mind when selecting the best deck sealer and why the products below are among the top options on the market in their respective categories.

  1. BEST OVERALL: SEAL-ONCE MARINE Wood Sealer, Waterproofer & Stain
  2. RUNNER UP: Rust-Oleum Ultimate Spar Urethane
  3. BEST FOR WATERPROOFING: Thompson’s Water Seal VOC Wood Protector
  4. EASIEST TO USE: Eco Advance Wood Siloxane Waterproofer Concentrate
  5. BEST FOR COLD TEMPERATURES: Olympic Stain 56500-04 Maximum Waterproofing Sealant
  6. PRESSURE TREATED WOOD PICK: Thompson’s Water Seal Transparent Waterproofing Stain
  7. COMPOSITE DECK PICK: DEFY Composite Deck Waterproofing Sealer
  8. ALSO CONSIDER: Olympic Stain Smartguard Concentrated Sealant
The Best Deck Sealer Options

Photo: amazon.com

Before Buying Deck Sealer

Before choosing a deck sealer, be sure that it’s the correct product for your needs. Sealer, stain, and paint can all protect your deck from the elements, though each one has different features.

Paint is typically a better choice on worn decks with mismatched boards or stains that won’t come off because it covers up these issues while offering an attractive uniform finish. While using a clear sealer will prolong the useful life of an older, weathered deck, it won’t update the deck’s look.

Stain, like paint, changes the color of the wood. However, instead of forming a topcoat, stain penetrates the wood fibers in the same way as sealer. Stain is beneficial for evening out splotchy color while maintaining the beauty of natural wood grain.

Deck stain imparts a natural-looking wood color, but depending on the opacity, it can provide just a hint of color or it can completely obscure the wood grain, like a paint. In addition, some deck sealers include a tint—these stain and sealer combos are helpful for both protecting and refreshing the look of the wood.

What to Consider When Choosing the Best Deck Sealant

While some types of wood naturally resist damage from water and insects, such as cedar and redwood, the most common material for new deck construction is pressure-treated wood. Treated wood is saturated with chemicals to help it resist moisture damage, but this type of wood is not invincible when confronted with Mother Nature. Even pressure-treated wood will begin to show signs of wear, such as warping and splintering, within a few short years if it’s not protected.

A quality deck sealer will create a water seal on the wood to help extend the useful life of the deck. Before buying, users should consider the type of sealer best suited to their individual needs and the specific protection the deck requires.

Oil-Based vs. Water-Based

You’ll find both water-based and oil-based deck sealers on the market, although users typically choose water-based products. Still, both types have their pros and their cons.

  • Ease of application: Oil-based sealers can be tricky to apply. If the deck isn’t dry when you apply an oil-based sealer, it’s likely to develop tiny bubbles or spots as the moisture tries to evaporate. Water-based sealers are safe to apply over slightly damp, though not wet, wood. Oil-based sealers are typically applied with a paintbrush, while water-based options can be brushed or sprayed onto the wood. Paint rollers aren’t common for applying deck sealer, regardless of the base.
  • Environmental concerns: Water-based sealers emit fewer toxic fumes, making them less irritating to your eyes and lungs and better for the environment.
  • Cleanup: Oil-based sealers require paint thinner or a similar solvent to clean brushes and tools after application, whereas water-based sealers clean up easily with just soap and water.
  • Durability: Particularly if the weather is extreme, water-based sealers can flake or chip over time, which is rarely a problem with oil-based sealers.
  • Preparation: When it’s time to reseal a deck, oil-based sealers are often more forgiving than their water-based counterparts. DIYers will still need to clean and prep the deck before applying either type of sealer, but oil-based products are generally a little easier to smooth on evenly over slightly rough wood or imperfections.
  • Cost: Oil-based sealers are usually less expensive than water-based products, which often cost twice as much per gallon.
  • Sheen: While water-based sealers rarely provide a finished sheen on the wood’s surface, oil-based sealers will often impart a slight sheen.

VOCs

Applying deck sealers, deck stains, or stain and sealer combo products, especially if they’re oil-based, can leave DIYers with headaches, burning eyes, or irritated nasal passages. This is due to fumes released by volatile organic chemicals (VOCs). In deck sealers, these VOCs are in the form of solvents designed to prevent sealer ingredients from separating and ensure a durable finish.

While no government regulations exist that specify the amount of VOCs permissible in deck sealers, manufacturers are constantly trying to reduce the amount of toxins while still producing quality products. The result is low-VOC and no-VOC sealers that emit fewer toxic fumes and are healthier for people and the environment.

  • Low-VOC: Deck sealers labeled “low-VOC” contain less than 50 grams per liter (g/L) of VOCs. Compare that to some high-VOC sealers that may contain as much as 300 g/L.
  • No-VOC: Sometimes labeled “zero-VOC,” these deck sealers contain very few—or no—VOCs. To qualify for the no-VOC label, products should contain less than 5 g/L.

Water and Mildew Resistance

If deck wood remains unsealed, moisture eventually leads to swelling, splitting, and rot. Unprotected decking boards are also prone to warping as they swell and contract with moisture variations. Deck sealer helps protect the wood from the damaging effects of moisture, including rain, snow, humidity, and sprinkler runoff.

Good deck sealers, like deck paints, may include mildewcides, which are chemicals that kill fungal spores. In damp climates, the growth of mold or mildew on wooden decks can be frustrating because the white or black splotches are unsightly and difficult to eliminate. If you live in a rainy or high-humidity climate, look for a sealer that fights fungus as well as moisture.

UV Protection

The sun’s ultraviolet rays are merciless: Beating down day after day, they can damage the cell walls of all living things, including wood. That damage shows up on a wood deck as fading, cracking, and splintering. Deck sealers often provide UV protection thanks to added ingredients, such as tiny zinc particles that block harsh sun rays.

These ingredients tend to break down fairly quickly, however. This can occur even within a few months in a scorching and sunny climate. While deck sealers vary in durability, consider reapplying a simple, water-based sealer each year before summer sets in to ensure optimal UV protection.

Coats

Most deck sealers require two coats for the best performance, though a few products can get the job done with just a single coat. That’s a big time-saver, although users will pay more for a single-coat sealer.

A water-based, penetrating sealer will often slightly raise the wood grain, which can lead to a rough surface feel. This happens when the moisture in the sealer causes the wood grain to swell and push upward. When the wood dries, the grain remains slightly higher in spots.

While some may not mind the rough texture, those who want a super-smooth finish should lightly sand the surface with 240-grit sandpaper before applying a second coat of sealer. No pressure is necessary—just lightly rub the sandpaper over the wood. Since the first coat seals the wood, the second coat will not raise the grain, and the result will be a smooth deck surface.

Drying Time

Deck sealers vary in the amount of drying time they require. Many will dry to the touch within 1 to 5 hours, but humidity levels and outdoor temperatures can affect that time range.

  • Water-based sealers: A coat of water-based sealer typically dries to the touch within 1 to 3 hours as long as the temperature is between 60 and 90 degrees Fahrenheit and the humidity is 50 percent or lower. Users can apply a second coat a few hours after the sealer is dry to the touch. Cure time (when the sealer has dried sufficiently for placing heavy furniture or walking) can be up to 24 hours.
  • Oil-based sealers: An oil-based sealer usually dries to the touch within 4 to 12 hours, and users can apply a second coat in about 24 hours. Some newer oil-based sealers contain quick-dry additives that may shorten dry and recoat time. Cure time can be up to 72 hours.

Our Top Picks

The best deck sealer meets a user’s needs for appearance, budget, application, and drying time in addition to fighting the effects of the elements. The following deck sealers are among some of the industry leaders for maintaining wood decks, chosen across a variety of categories.

Best Overall

The Best Deck Sealer Option: Seal-Once Marine Premium Wood Sealer
Photo: amazon.com

This penetrating wood sealer is water-based but provides the protection users expect from an oil-based sealer. This sealer penetrates right down into the wood fibers for long-lasting protection against UV and moisture damage and mold growth. It goes on clear and doesn’t impart a shine to the deck.

Since the sealer penetrates the wood rather than merely forming a coating, it expands and contracts as the wood fibers respond to temperature changes. This means no fear of cracking or peeling, even in the hottest summers or coldest winters.

The sealer is also ultra-low in VOCs, so it won’t harm people, pets, plants, or marine life. It also cleans up easily with soap and water and helps the deck resist damage from water, salt spray, mold, and algae.

Runner Up

The Best Deck Sealer Option: Rust-Oleum 9441 Ultimate Spar Urethane Oil Based
Photo: amazon.com

Protecting the backyard deck doesn’t have to cost a fortune. Rust-Oleum’s oil-based sealer adds a layer of defense against the elements. The sealer creates a water-resistant barrier, so rain beads up and runs off instead of soaking into the wood. It also contains UV protectants to keep harsh sun rays from fading the wood’s natural hue.

This sealer also offers a measure of protection against mold and mildew, making it well suited for decks in humid areas. The durable coating will expand and contract to reduce the risk of cracking, and it also resists scratches. Since this is an oil-based sealant, an application of two or three coats can last up to 5 years or longer.

Best for Waterproofing

The Best Deck Sealer Option: THOMPSONS WATERSEAL 21802 VOC Wood
Photo: amazon.com

The clear, penetrating protection of this wood protector adds a robust level of defense against the elements—without changing the wood’s natural color or adding a sheen. That makes the product well suited to use on exterior woods like cedar and redwood.

The water-based sealer contains UV blockers and also protects decks from mold and mildew damage, so it’s an optimal choice in humid and rainy areas. It is designed to repel water with just one coat and also features reduced VOCs. Apply a coat of this wood-protecting sealer with either a brush or a sprayer, and it will last up to 3 years before another application is necessary.

Easiest to Use

The Best Deck Sealer Option: Eco Advance Wood Siloxane Waterproofer Concentrate
Photo: amazon.com

There’s no need for a backbreaking day of applying sealer when you use this concentrate from Eco Advance. Just mix the concentrate with a gallon of water, pour it into a garden or deck sprayer, and cover the deck with a light coat of the formula.

This deck sealer goes on milky white, making it easy for users to see where they’ve already applied the spray. However, it dries crystal clear in less than 2 hours and will not change the look of the decking or leave a sheen.

Even better, this water-based formula won’t harm the surrounding lawn or outdoor plants. It’s low in VOCs, odorless, and is nontoxic to people and pets. With protection against moisture, mold, pool chemicals, de-icers, and oil, the deck will look its best all year long.

Best for Cold Temperatures

The Best Deck Sealer Option: Olympic Stain 56500-04 Maximum Waterproofing Sealant
Photo: amazon.com

Stop waiting for perfect weather to apply deck sealer. Most deck sealers require temperatures of 55 degrees Fahrenheit or higher before application, but Olympic Stain’s sealant goes on smoothly even when it’s as chilly as 35 degrees Fahrenheit. Users can even apply it on damp wood after a rain shower.

The water-based sealer includes UV blockers to ward off fading and warping from sun exposure, and it protects a deck from rotting, cupping, and staining due to water or humidity. It also won’t change the look of the deck or add a shine. One coat will last up to 3 years.

Pressure Treated Wood Pick

The Best Deck Sealer Option: THOMPSONS WATERSEAL TH.041811-16 Transparent Stain
Photo: amazon.com

Over time, pressure-treated wood can take on an unappealing greenish tint. A deck sealer that offers a hint of color will add an attractive uniform shade while protecting the wood. This option from Thompson’s Water Seal is both a wood stain and a sealer all in one.

Ideal for protecting treated wood decks while giving them a touch of color, this water-based sealer offers optimal UV and moisture protection with just one coat, and it also resists mold and mildew growth. It lasts up to 3 years.

Composite Deck Pick

The Best Deck Sealer Option: DEFY Crystal Clear Composite Deck Waterproofing
Photo: amazon.com

Specially formulated for use on composite wood decks, DEFY’s waterproofing sealer includes tiny zinc particles that deliver superior protection against harmful UV rays, preventing fading and graying. Along the way, the product adds a soft, semi-transparent sheen.

Users can apply the DEFY sealer with a pump sprayer or by brushing it over a clean deck. Note that while this deck sealer is optimal for wood composite wood decks that have become porous, it’s not meant for sealing new composite wood decks that still have a nonporous finish. One coat will renew and guard decks against UV rays and moisture for up to 3 years.

Also Consider

The Best Deck Sealer Option: Olympic Smartguard Concentrated Sealant
Photo: amazon.com

Looking for quick deck protection? You can apply Olympic Stain’s concentrated sealant in the morning and walk on the deck later the same day.

This quick-dry sealer comes in concentrated form—just pour the product into a garden or deck sprayer, add water, and spray the deck evenly to protect it from the elements. The penetrating formula seeps into the wood grain to form a strong defensive barrier.

The sealer dries in just 1 hour—even on wood that’s damp from rain or a recent washing. It protects the wood but does not change the appearance or impart any sheen. The sealer prevents water damage, so the deck won’t rot, split, or warp.

How to Apply Deck Sealer

Applying a deck sealer is a relatively simple DIY project. In most cases, it doesn’t require a lot of time, although some prep work is necessary.

  • Clean the deck with a deck cleaner designed to remove existing dirt, grease, and grime.
  • Sand down any rough spots.
  • Apply the sealer based on manufacturer recommendations; most require diluting with water and spraying with a pump-type sprayer, or brushing it on with a paintbrush.

FAQs About Deck Sealers

Exterior wood is subject to weathering, so a deck won’t last forever. However, DIYers can prolong the useful life of a deck and maintain the natural beauty by protecting it with a deck sealer. For those hoping to keep a deck looking its best, a few questions are to be expected to ensure a job well done.

Q. Is it better to stain or seal a deck?

It depends on the type of wood. Weather-resistant woods, such as cedar or redwood, need only a clear penetrating sealer to protect them. Pressure-treated wood will benefit from a stain and sealer combo that gives it an attractive color while preserving the wood.

Q. What is the longest-lasting deck sealer?

An oil-based deck sealer, such as Rust-Oleum Ultimate Spar Urethane, will protect a deck for up to 5 years.

Q. What is the best waterproof deck coating?

Thompson’s Water Seal VOC Wood Protector is one of the best options in this list for superior protection against water damage.

Final Thoughts

An outdoor deck serves as an extension of a home’s living space, offering a welcoming place to entertain and enjoy the outdoors. Applying a quality deck sealer will keep a deck looking its best for as long as possible.