How to Clean a Wood Deck and Treat Stains

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With the price of lumber on the rise, it’s more important than ever to clean your deck properly and protect it from stains.

Patio table with an umbrella sits on a clean wood deck attached to a suburban home.

Why You Should Clean Your Deck

If left uncared for, a deck will develop permanent stains, splinters, and even mold and mildew. That’s because wood, being a porous substance, expands and contracts as temperatures vary. And that expansion lets dirt and grime work their way deep into the wood over time.

That grime can also cause your wood deck to warp and rot more quickly. Rotting decks are dangerous, too. Fortunately, with regular cleaning, you’ll know if your deck is starting to have problems.

How To Clean Your Wood Deck

Set aside a sunny afternoon to give your home’s wood deck a thorough cleaning with or without a powerwasher.

Equipment and Materials You’ll Need:

  • A broom
  • Tarps to cover items below the deck
  • Bucket
  • Stiff scrub brush
  • Garden hose
  • Oxygenated bleach (non-cholorine bleach)
  • Power washer (optional)

Inspect and Sweep

1. Remove everything from the deck. This includes chairs, planters, grills, toys, etc. If you can’t remove it all, you’ll have to work in two parts, moving things to one side of the deck while you work on the other.

2. Inspect the structure. Grab your broom and clean the exterior walls of the house where the deck attaches to it. Inspect the flashing and ledger where your deck is connected to your home. If you notice screws that have worked loose, replace them with new decking screws. If you see signs of rot, a licensed contractor may be able to replace only the damaged portion.

3. Sweep. Use the broom on your deck’s railing first and remove any cobwebs or other debris. Then sweep the top of the deck. If it’s a second-floor deck and you can get beneath it, go ahead and clean the underside to eliminate debris that will collect moisture.

Treat Stains on Your Deck

1. Spread tarps. Although the deck-washing solution you’re going to use is safe for plants, you may not want it to get on other things near your deck like your BBQ grill or outdoor toys. Protect them with tarps if you like.

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2. Make this DIY deck-cleaning solution. In the bucket, stir 1 cup of oxygenated bleach into 2 gallons of hot water until fully dissolved. Working in sections, spread the cleaner on your deck and allow it to sit for 5 minutes. You may see it bubble a bit as it tackles the stains. Use the scrub brush to scour the surface, then rinse. Repeat this on the rails, stairs, etc.

3. Rinse again. Once you’ve finished scrubbing everything, rinse your deck from top to bottom, including the railings, surface, and stairs. Also, rinse any tarps you used to cover nearby items so they don’t dry with a layer of grime on them.

4. Let it dry. Don’t put anything back on your deck until it is completely dry. Damp wood is fragile, so moving heavy furniture or grills can gouge your wood. Also, putting things like outdoor rugs or furniture on wet wood will cause mold.

How to Power Wash Your Deck

Plan to follow these steps to powerwash your deck when there’s no rain or freezing temperatures in the forecast for at least a full week. Pressure washing sends water deeper into your deck’s surfaces than a hose does, so the wood will take longer to dry.

1. Clear and sweep it first. Before power washing, perform the steps above to inspect and clean your deck.

2. Lower pressure is better. A power washer can make a weathered deck look like new as it blasts away grime and discoloration. Too intense of pressure can damage your deck, though, so keep the setting under 1500 pounds per square inch.

3. Constant, overlapping strokes. Even a 1500 lbs/psi setting can damage soft or composite wood if you’re not careful. Don’t aim the power washer at any one spot for long. Use overlapping long, sweeping strokes starting where the deck meets your home and working your way outward. \

4. Keep proper distance. Keep the pressure washer’s nozzle at least three feet from the deck surface and work in the direction of the wood grain. To clean railings, turn the pressure down to 1000 lbs/psi and work from at least three feet away as you spray them in overlapping quick vertical strokes.

5. Sweep away standing water. Once you’re done power washing your deck, use a broom to sweep away standing puddles of water. This will help your deck dry faster and reduce splintering. Give your deck at least two full days to dry before putting furniture or outdoor rugs back on it.

Maintenance, Sealing, and Painting

Keep your deck swept throughout the year, so fallen leaves and other debris don’t trap moisture that can make your deck rot or develop mold. If you live in a snowy area, you should also shovel snow off of your deck whenever you shovel the driveway. Allowing snow to build up adds an enormous amount of weight to your deck, and the melting snow can also cause your deck’s wood to warp.

If you plan to seal or paint your deck, first give it a deep clean using one or both of these methods. Then, let it dry for at least a week before applying surface treatments. To test whether it’s dry enough for sealant, sprinkle a quarter cup of water on the wood. If the deck absorbs the water in 5-10 minutes, it’s dry enough. If the droplets stay on the surface longer than that, the wood is still too wet.

When you’re ready to reseal, use a pad or foam roller to apply the sealant or paint. For most decks, deep cleaning and sealing once a year is enough. Don’t go longer than three years without reapplying sealant, or your deck’s wood may begin to warp and split.

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