How to Seal Your Deck

Decks are the stage for family barbecues, peaceful mornings with coffee and cool evening gatherings under the stars. They also enhance the aesthetic appeal of your home.

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But these outdoor spaces are continually exposed to the elements (sun, rain and snow) that can cause them to deteriorate and lose their charm if not adequately protected. When you seal your deck, you help to preserve its beauty and maximize its longevity. Read the tips below and learn what type of sealer to use, how to seal your deck and how often you should seal your deck.

Things You’ll Need:

• Deck sealer
• Paint mixing stick or mixing paddle and electric drill
• Garden hose or pressure washer
• Deck cleaner
• Garden sprayer (optional)
• Stiff-bristled brush (if necessary)
• Plastic sheeting
• Paintbrush
• Paint roller
• Paint pan
• Power sander or block sander with 60 to 80-grit sandpaper (if necessary)

Step 1: Choose the Right Sealer

Deck sealers are available in different finishes that offer varying levels of protection from the elements, aesthetic attributes and maintenance requirements. The finish that’s best for your deck will largely depend on your climate (whether your deck is exposed to a lot of sun, rain or both), the finished appearance you desire and how often you’re willing to reapply the sealer to keep your deck protected.

Options include:

• Clear sealers: Clear sealers provide the least UV and moisture protection as they do not contain any pigment. However, they do provide a basic level of protection and mostly help to repel water, reducing the risk of wood rot or mold. Their main benefit is that they allow the wood's natural beauty to shine through and are ideal if you want to maintain the natural look of the wood. Clear sealers may need to be reapplied every year or two to maintain their effectiveness.
• Tinted or toners: Tinted sealers contain a small amount of pigment that can enhance the natural color of the wood and provide slightly more UV protection than clear sealers. They still need to be reapplied relatively frequently (every two to three years), and while they offer more protection than clear sealers, they don't protect as well as semi-transparent or solid sealers.
• Semi-transparent sealers: Semi-transparent sealers provide a good balance between showing the wood's natural grain and providing a solid level of protection against both water damage and UV rays with their moderate level of pigment. They typically only need to be reapplied every three to four years. However, over time (especially with exposure to sunlight,) semi-transparent sealers may start to peel or flake, requiring more maintenance.
• Solid or opaque sealers: Solid sealers offer the highest level of protection against water damage and UV rays. They are a good choice for older decks with imperfections, as they can hide stains and discolorations. However, they completely cover the wood's grain (acting more like a paint than a sealer) and can peel over time, especially if not applied properly.

Step 2: Clean the Deck

Cleaning the deck effectively prepares it for the sealing by promoting proper adhesion to the deck’s surface. Start by removing everything from your deck, including furniture, barbecues and potted plants.

Once your deck is cleared, sweep or blow it off to remove any leaves, twigs, dirt and other loose debris. Also address the spaces between the deck boards where debris can become trapped.

Next, apply a specialized deck cleaner. Deck cleaners are specifically formulated to remove dirt, mildew, algae and other substances that can prevent the deck sealer from adhering properly. There are several types of deck cleaners available, including those designed to remove mold and mildew, stains and general grime. There are also cleaners designed for specific types of deck boards, like pressure-treated. Choose a deck cleaner best suited for your deck’s specific condition and the type of wood it's made from, if applicable.

Regardless of the cleaner you use, cover surrounding plants and items with plastic sheeting to protect them from exposure to the cleaner - as many are corrosive. Next, follow the manufacturer's instructions to prepare the deck cleaner. Some cleaners need to be diluted with water, while others are ready to use.

Once prepared, use a garden sprayer or paint roller to apply the cleaner to the deck. Start from one end of the deck and work your way to the other, ensuring that you evenly cover all areas. For stubborn spots or areas with mold or mildew, use a stiff-bristled brush to scrub the deck.

After the cleaner has been applied to your entire deck, allow it to sit on the deck for a period of time specified by the manufacturer. This lets the cleaner penetrate the wood and lift out the dirt and grime.

Finally, rinse off the cleaner thoroughly using a garden hose or a pressure washer on a gentle setting. Ensure all the cleaner is rinsed off, as leftover cleaner can interfere with the sealing process.

Allow the deck to fully dry.

Step 3: Sand the Deck

If your deck is new and the surface is already smooth, or if it's been maintained well and the old sealer is worn but not peeling, you might not need to sand it at all. However, if the deck surface is rough, there are splinters or the old finish is peeling and flaking, sanding is beneficial to ensure a smooth surface for the sealant to adhere to.

If sanding is required, use 60- to 80-grit sandpaper installed onto a manual block sander or power sander to smooth down any rough areas. Sand along the grain of the wood to avoid unnecessary scratches or damage to the wood. If you're using a power sander, keep it moving at all times to prevent creating depressions in the wood surface.

After sanding, sweep or blow off your deck to remove the sanding dust, then rinse it with a garden hose to ensure all the dust has been cleared off. Allow the deck to completely dry.

Step 4: Apply the Sealer

Mix the sealer thoroughly with a paint mixing stick or mixing paddle installed on an electric drill.

Begin applying the sealer using a paintbrush to paint a border around the edge of the deck where the roller won’t be able to reach (also known as “cutting in”). Use the brush to apply sealer to the spaces between the deck boards. These areas can trap moisture and lead to rot, so it's important to seal them as well.

Next, pour some sealer into a paint tray and use a paint roller to apply the sealer to the rest of your deck. Start at one end of the deck and work your way to the other, applying the sealer along the length of the boards. Try to maintain a "wet edge". In other words, don't let the sealer dry where you're still working. This can help to prevent lap marks, which occur when wet sealer is applied over dried sealer.

After applying the sealer, let it dry according to the manufacturer's instructions. Drying times can vary depending on the type of sealer, the temperature and the humidity. In general, you should expect to wait at least 48 hours, but it may take longer to completely dry in humid conditions.

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How Often Do You Need to Seal Your Deck?

The frequency of deck sealing depends on several factors, including the type of sealer used, the weather conditions in your area, the type of wood your deck is made from and how much wear and tear the deck gets. On average, most decks need to be sealed every two to three years.

However, there are signs that can indicate when your deck needs to be resealed. If the color of the deck starts to fade, if the water no longer beads up on the surface of the wood or if you notice any cracking or peeling, it's likely time to reseal the deck.