How to Seal a Deck

Last Updated: October 22, 2022

Exposed to the elements and walked over, scratched, and scraped, wood decks tend to develop mold and other problems rather quickly. Although a quick wash might make your deck look nicer, anything short of a good sealing will leave you with crumbling planks and unappealing colors. Deck sealing is best done before the rainy season and when you know there will be lots of sun for your deck to dry under. This article will teach you how to seal a deck with water-resistant sealant that can stand up to harsh weather.

Steps

1
Test the water resistance of your deck by spraying some water from a hose onto its surface.
- If the water beads up on the surface of your deck, you don't need to seal. If the water seeps into the wood, you need to seal. A deck that traps water will bend, warp and ultimately weaken.
2
Choose a deck sealer appropriate for your type of wood. Most sealers will work for any wood.

Advertisement
3
Spray down the deck with water so that its entire surface is wet.^{[1]
X
Research source}
4
Wipe down the deck meticulously with a scrub brush, removing all leaves, mold, and other material that has collected on the surface.
- If you do not have a very clean deck before sealing, the deck sealer will trap in all the elements you want removed, and your problem will be exacerbated. Remember to clear any plant or anything else that could be hurt by deck sealer.
5
Rinse the deck again to clear any debris.
6
Let the deck sit for at least a day until completely dry.^{[2]
X
Research source}
7
Apply the deck sealer with a mop or paint roller in a corner of the deck, following any instructions provided.^{[3]
X
Research source} Use even strokes, making sure not to allow sealer to collect anywhere. Move out from the corner in such a way that you can apply sealer to the whole deck without stepping in it.
8
Go over the deck only once, using deck sealer sparingly. The entire deck should be covered in an even coat of a single color.
9
Let the deck sealer dry for at least a day before walking on it.

Community Q&A

Question

What about the underside of the deck?

Community Answer

You don't have to paint or seal the underside of a deck because it is not exposed to much sunlight or rainwater.
Question

Can I wash the deck with a pressure cleaning machine before to seal it?

Community Answer

Yes. Make sure the deck is dry before you seal it. If you use a detergent when you pressure wash, rinse the deck off to remove all the detergent before you let it dry.
Question

What about a deck that is already painted? The paint is fine but there are some spots (like over knots) that are exposing the wood. I don't want to strip the whole deck - what can I do for these?

Community Answer

After the deck is dry from cleaning you can just paint over any paint that won't come off.

Warnings

Deck sealer includes dangerous chemicals that should not come into contact with your eyes or mouth. Always use gloves and wear glasses if your eyes become sensitive.

⧼thumbs_response⧽
Helpful 8 Not Helpful 7
It's common to use a power washer rather than a hose to wash down a deck. However, power washers can damage sensitive or old wood and create unsightly gashes. If you have doubts about the strength of your wood, stick with a hose.

⧼thumbs_response⧽
Helpful 9 Not Helpful 10
A water-resistant deck is not necessarily a strong deck. Before applying deck sealer, check the strength of all your planks for rot. Remove rotted wood.

⧼thumbs_response⧽
Helpful 5 Not Helpful 9