The surface of your wooden deck can be damaged by extreme heat and cold if it doesn't have a protective coating. Sealing and staining are both ways to protect and keep your deck in good shape, but sealing has some benefits that staining doesn't.
Deck Sealer
Deck sealer is usually a clear coat that soaks deep into the wood and forms a clear film on the surface while keeping the natural look of the wood. By getting into the wood, the sealer makes a protective layer that helps keep water out and keeps moisture from getting in. Fungal growth and wood rot can both shorten the life of your deck, so it's important to use this protective finish. Deck sealer slows down the damage caused by water, but it doesn't do a good job of protecting against UV rays. Even with a sealer, direct sunlight will eventually dry out the natural oils in the wood, which will cause it to fade and crack and split.
Read more: How to Avoid, Prevent and Repair Deck Joists Rot
Deck Stain
Deck stain also makes the wood resistant to water, and it can add color to the wood in different ways, from being semi-transparent to solid. Also, many stains come in many different colors, so you can get a wide range of colors when you're done. Since stains have color added, they are better at blocking UV light and offer more protection than a sealer alone. In fact, the darker the stain, the more pigment is added, which protects your deck even more.
Read more: How to Anchor Deck Stairs to Concrete
Applying Deck Sealer to a Wood Deck
To get the best seal possible, make sure your deck is clean before you put on the sealer. Make sure to get rid of all the dirt, dust, grime, and mildew. Check out our step-by-step guide to learn how to clean or pressure wash a deck the best way.
Before we talk about how to seal a wood deck step by step, there are a few things to keep in mind. First of all, don't put deck sealer on in direct sunlight, because the finish will dry too fast. The sealant needs time to soak into the wood well. Also, if you have a brand-new deck made of treated wood, you should wait a few weeks to stain it. This will give the wood time to dry out completely, which will help the stain soak in better. You're now ready to start!
Read more: How to Lay Out Deck Stair Stringers
Step 1: Check the forecast
Make sure you have at least two days of dry weather with temperatures between 50 and 90 °F before you start to seal your deck. This will make sure that the best seal is made.
Step 2: Clear the deck
Probably goes without saying, but you don't want to start sealing your deck with furniture, plants, and other items all over the place.
Step 3: Sand (if needed)
You may need to sand your deck before sealing it to make sure the sealer gets into the wood well. Sanding takes time, but it is often necessary. You can speed up the process by using a pole or palm sander, but make sure to sand in the direction of the wood's grain. When you sand, always wear a safety mask so you don't breathe in sawdust.
Step 4: Remove debris
After sanding, you'll want to make sure there are no loose pieces of wood on the whole deck. That means cleaning between the cracks and making sure the deck is completely dry.
Step 5: Stir sealer
Make sure to stir the sealer before you use it. DO NOT shake. If you shake the finish, bubbles may form.
Step 6: Apply sealer
Use a paintbrush, roller, or sprayer to spread a thin coat of paint over two to three boards. You can always add another thin coat later, as it will go on and dry better than one thick coat.
To make the best coat possible, back-rolling may also be needed. For this, you need one person to put on the seal and another to use a roller or broom to spread out puddles and work the finish into the wood well.
Step 7: Repeat & fine tune
Step 6 must be done for the whole deck. Use a finer paintbrush to apply the sealer to cracks, railings, and steps, which are hard to reach.
Step 8: Let it dry
Before using the deck, let it dry completely.
Read more: How to Cut Deck Stair Stringers
Best Deck Sealers
Protecting your deck is much cheaper than building a new one, so don't leave it out in the weather, which will cause it to wear down, rot, and grow mildew. To make your deck last longer, take action early and often with good deck stains and sealers.
But how do you know which deck stains and sealants are the best? Which ones can you count on to stand up to the weather and everyday use? Some of the best deck sealers on the market are listed below:
Thompsons Waterseal Advanced Natural Wood Protector
Thompsons is one of the best water seals on the market, so it will protect your deck from mildew and water damage. It will also help prevent long-term UV damage and color fading.
Read more; How to Remove Ink Stamps from Pressure Treated Lumber
ECO-SAFE Wood Treatment – Stain & Preservation by Tall Earth
Tall Earth's ECO-SAFE Wood Treatment is great because, as long as your deck is clean, it can be used right away without any special preparation. You only need one coat to protect yourself; you don't need to put on more than one.
Read more: Removing Moss & Algae from Your Deck
Rust-Oleum Coppercoat Wood Preservative
This EPA-approved deck sealer has all the benefits of a good sealer and also keeps termites and ants away from your deck. After you put it on, you might see a thin, clear green layer, but it will go away over time.
CabotStain Australian Timber Oil Penetrating Oil
CabotStain is a high-quality sealer that will go deep into even the hardest types of wood. Unlike most other sealers, it has iron oxide pigmentation that can help protect wood from UV damage.
Thompsons Waterseal – Transparent Stain
This deck stain and sealer combo is the best of both worlds. It gives the deck a transparent color and makes the surface waterproof to protect it from mildew, rot, and mold. It is easy to use and dries quickly after being applied.
FAQs
Sealer vs. stain—what’s the difference (and can one product do both)?
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A sealer is usually clear and focuses on water repellence; a stain adds pigment for UV protection (semi-transparent to solid). Many modern products are stain-and-sealer combos if you want one step.
When’s the best weather window to seal/stain?
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Aim for 2 dry days with temps roughly 50–90 °F (10–32 °C) and avoid direct sun so the finish can penetrate evenly.
How do I prep correctly—cleaning, sanding, and drying?
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Clear furniture, clean (deck cleaner/oxalic or oxygen-bleach solutions), rinse, let the wood dry, and sand raised grain (≈80–120 grit). Keep washer PSI modest to avoid gouging soft PT wood.
How do I know the deck is dry enough to accept sealer/stain?
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Use the sprinkle test (water should absorb, not bead) and/or a moisture meter; many pros look for ≤ 15% moisture before coating. Also wait ~48 hours after pressure washing.
New pressure-treated wood—can I seal/stain right away?
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Not usually. Let PT lumber dry first (watch for the sprinkle-test to pass; timing varies by climate and whether it’s KDAT).
Brush, roller, or sprayer—and what is “back-brushing/back-rolling”?
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All three can work, but always back-brush/back-roll to work product into the grain and even out lap marks—especially with ridged boards.
How much product will I need (coverage per gallon)?
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Check the label, but expect about 250–350 sq ft/gal for many stains/sealers (older, rougher wood may be 150–300). Use brand calculators to dial it in.
How long should I let it dry/cure before use or recoating?
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Plan 24–48 hours of dry weather (longer in cool/shady conditions). Follow your product’s TDS for foot traffic and furniture reset.
How often should I re-seal or re-stain?
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Expect 1–3 years depending on product opacity, exposure, and traffic. Semi-transparent finishes generally need more frequent refresh than solids.
Oil-based vs. water-based (and opacity)—which lasts longer?
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Oil-based tends to penetrate deeply and can last longer between coats; water-based is low-odor and fast-dry but may need more frequent maintenance. More opaque (semi-solid/solid) usually = longer life but hides grain more.
