How to Seal a Deck

A deck with plants
  • 3-5 hours
  • Intermediate
  • 50-100
What You'll Need
Deck sealant
Belt sander with a medium-fine grit
Plenty of spare sandpaper
Face mask
Safety glasses

Sealing a deck is an important part of the construction and consequent maintenance of a wood deck. In order to get your money’s worth out of the lumber, you should seal it to protect it from the elements like precipitation, wind, sun, and cold. There are deck sealing products on the market which contain tint, or color, to keep the integrity of your wood’s grain but still adding visual interest by changing the hue of the wood. You can also find products that are built towards your specific needs, such as sealants for humid areas or for dry and extremely sunny areas, like the desert. Knowing what’s on the market today will make choosing the ideal sealant for your local climate much easier.

Step 1 - Sand Wood

Before you pick up anything, remember this extremely important information: do not sand against the grain. The grain of the wood should run up and down the length of the boards, which makes them strong enough to be deck wood in the first place. First of all, if you sand against the grain, you’re making the surface weak against moisture and putting grooves into the wood that will ultimately shorten the life span of your deck sealant. As a result, your sander should move in the same direction as your boards, end to end.

Put on your safety goggles and face mask. Now you can sand your deck. If your deck is unfinished and you’re sealing it as the final part of the building process, you won’t have to sand it at all. However, in many cases, a deck is built for you or is already constructed on the home you bought, and so getting rid of whatever is on the surface of the wood is crucial to seal it properly. Just take off the top layer, don’t sand too deep—you only want to remove the current sealant and leave bare wood. Do this on the entire surface of your deck (it may take several hours depending on the surface area you have to cover).

Step 2 - Clean Sanding Dust Off

While this could be self-explanatory, it is still worth mentioning because the sanding dust that you created taking off will have a crusty tendency to it and should be swept out from the cracks in between planks. Make sure your surface is particle-free and ready for the first coat of sealant.

Step 3 - Apply Sealant

All the prep work leads up to this: applying your deck sealant. You will probably need two coats. The coverage that a single gallon of sealant can give you will depend entirely on the make and purpose of the product—some will give you twice as much as others, but might not be right for high humidity or high sun climates.

Dip your brush in the bucket, and moving in the direction of the wood grain, paint a single even coat over the wood, making sure to dip the brush into the crevices of the planks as well. Then step away and let it dry.

Repeat this process for the second coat.

You’re all finished sealing (or re-sealing) your deck. You can stand back and stretch, work out some of the soreness in your body, and go relax somewhere else while the sealant dries. Within a day of putting your sealant on, you can enjoy your outdoor space knowing you took the right steps to extend the years of use you can get out of your deck.