How to Properly Clean a Deck

A good deck cleaner will remove accumulated dirt, mildew, and mold. It should be safe for both natural and composite wood and will not damage masonry, metal, or fabric outdoor furniture and decorations.

Deck

Using a garden hose with a spray nozzle, apply the cleaner to the deck surface and let it soak for the recommended time. Rinse well with clean water.

Before you start cleaning, make sure the deck is completely clear and free of debris. This includes nails, screws, and other fasteners, as well as leaves and grass clippings. Also, if any lag screws are loose in the ledger board, rails, or posts, tighten them. Finally, sand rough or splintered areas with 80-grit sandpaper before proceeding.

You can use a broom and mild cleaner to get rid of the majority of dirt, but a power washer will be far more effective (and quicker). Just remember that it takes practice to learn how to operate a pressure washer safely. Keep it at a safe distance from the house, and always aim to spray water in the direction of the wood grain.

They are available in liquid or powder form and contain a special surfactant that helps lift contaminants from the surface of your deck. They’re also less toxic than chlorine bleach-containing products and don’t leave behind harmful by-products or residue.

An adduct of sodium carbonate (soda ash) and hydrogen peroxide, this powdered product works great for most average wood preparation jobs. It’s nontoxic with no contamination, nonflammable, and nonexplosive, and it dissolves completely in water. It’s also highly biodegradable, which means it doesn’t harm the environment or your plants.

Oxalic acid-based products are excellent for removing tannin streaks and iron stains around nail and screw heads in cedar and redwood decking. They’re also effective at whitening gray or dull areas that can’t be removed with bleach.

A special stain stripper is used for really stubborn stains that won’t budge, such as oil or grease. Follow the instructions on the package to apply it with a brush or power washer. If there are plants or shrubs near your deck, cover them with plastic to protect them from the stripper.

Preparation

A deck needs to be cleaned before it gets a new coat of stain. Stain will stick better to a surface that’s free of mold, mildew, and other contaminants. And you’ll save yourself a lot of work and money if you take the time to prepare the deck properly.

Begin by removing any furniture, plants, or other items from the deck. Then broom and sweep it thoroughly to remove any loose dirt, debris, or dust. If the deck is splintered or otherwise damaged, use wood filler to repair it before staining. If it’s a pressure-treated deck, apply one or more treatments to restore the wood, according to the product directions.

If the deck has been stained in the past, it’s important to strip those stains from the surface and from the pores of the wood. Stripping will prevent the new stain from bonding.

To strip a treated deck, choose a non-toxic, plant-friendly cleaner like Harris Deck and Fence All-Purpose Cleaner Concentrate. This cleaner has a lower pH than most bleach-based chemicals, which will help preserve the wood. Dilute it for general cleaning or use full strength on tough stains and grime. Cover any plants you want to protect, and wear rubber gloves, goggles, and a face mask when working with the concentrated cleaner.

For natural wood, a wood brightener such as Revive Deck and Siding Brightener is a great option. It can be used on cedar and redwood, as well as composite and untreated pressure-treated decking. This deck and siding brightener will neutralize the stain and sealer remover or other strippers and return the wood’s natural appearance and luster.

You can also strip a cedar or redwood deck using oxalic acid, a common vegetable acid that works well on these types of decks. Follow the manufacturer’s instructions on how to dilute oxalic acid and how long to let it sit on the wood. This will vary according to the type of deck and the severity of the stains. After the recommended amount of time, rinse and allow the deck to dry completely before sanding.

Power Washing

A power washer can be useful for cleaning a deck, but it’s important to use the right amount of pressure. Too much pressure can damage the surface and splinter timber. In addition, if the water is too hot, it can warp and stain the wood. In general, it’s best to avoid using a pressure washer unless you need it for extreme cases of dirt buildup or to prepare the deck for staining.

A deck made of treated wood should be cleaned with a cleaner formulated for that material. A diluted mixture of trisodium phosphate (TSP) and oxygen bleach is an effective cleaning solution for both concrete and wooden surfaces, according to Home Smiles. This powerful mix can remove mildew, mold, and stains and is safe for the environment and grass around a deck. The diluted TSP can also be used as a wood preservative.

Before you apply the cleaner to a deck, it’s essential to pre-rinse it to soften dried cellulose fibers and allow the cleaning solution to more easily disperse. Then, scrubbing with a stiff bristle brush removes dirt, mildew, mold, and stains from the wood surface. It’s important to remember that dragging furniture, grills, and other metal items across wet timber can scar or gouge the wood and leave rust stains.

It’s a good idea to wear gloves when mixing and applying any cleaning solution, especially if it is homemade. Some ingredients in DIY cleaners and boosting agents can cause skin irritation at high concentrations.

Composite decks can be cleaned with a solution of two parts vinegar to one part water or a commercial product made specifically for the material. Composite decks are more porous than those made of timber, so they can absorb a lot of contaminants, including oil and dirt, that can swell the boards and lead to cracking.

After cleaning a wood or composite deck, it’s a good idea to apply a deck brightener to restore the natural pH of the wood and help it absorb protection like stain better. A deck brightener that’s safe for your specific material should be available at a hardware store.

Staining

Staining your deck is a great way to protect it from the elements. Before you apply a stain, though, make sure you have a clean surface. A soiled deck isn’t going to look good and can actually make it more prone to damage. The best way to get a deck ready for staining is to follow the prep instructions on the stain you’re using. Many products will require that you first use a cleaner that removes dirt, mildew, and discoloration before you treat the wood with a brightener to open its pores. Other products may also require you to strip and sand before you can begin the staining process.

It’s best to do a thorough cleaning and brightening on a day that isn’t directly in sunlight. If possible, choose a day that doesn’t have a lot of humidity in the air as well. Humidity can slow down the drying time of your cleaners and cause moisture to get trapped under your new stain, which can lead to peeling and flaking over time.

Begin by sweeping away all the loose debris on your deck. Then, mix your cleaner according to the directions on the label. Load your brush with the solution and begin working on your deck in small sections. Work your way across the deck, scrubbing away dirt, mildew, and surface stains as you go. Make sure you’re scrubbing evenly, and use your hose to rinse the cleaner off of your deck boards as you go. Rinse in a circular motion to avoid streaking.

If you’re dealing with old sealers and stains, try using a powdered oxygen bleach product to get rid of them. These products are safe for the environment and your home, and they can be bought in most hardware stores. Just be careful not to mix it with any other household cleaners, which could harm the wood or cause the color of your deck to change.

After you’re done scrubbing, allow the deck to dry. You can usually tell it’s dry by feeling it, but if you want to be extra cautious, you can wait 24 hours before walking on your deck.