Outdoor living areas collect a lot of dirt and grime throughout the year. Learn how to remove stains on decks and patios, including greasy spills, mildew, rust, and other grimy buildup, for a spotless outdoor space.

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Decks, patios, and porches play host to a wide range of outdoor activities during the warmer months. A season's worth of alfresco cooking, dining, and entertaining can easily dirty the surface with spots from grill grease, food or drink spills, soot from the firepit, and more. And because these spaces are exposed to the elements, they can naturally gather stains from dirt, leaves, tree sap, rusty furniture, and other grime throughout the year.

Stains on decks and patios can be difficult to remove, but with the right cleaning method and supplies, you can get your outdoor space looking good as new. Keep in mind that wood decks and hard-surface patios (including those made from brick, cement, or flagstone) will require different approaches to avoid damaging the surface, and the best deck stain remover will depend on the type of stain. Use the instructions below to learn how to clean stains on decks and patios to restore your space for outdoor living.

multi-level back deck with outdoor dining, kitchen and lounge areas
Credit: Aniko Levai

How to Clean Stains on Wood Decks or Porches

Plan to clean stains on decks and porches as soon as possible to prevent the mark from setting into the wood permanently. In general, it's best to avoid using harsh chemicals to clean your wood deck. Chlorine bleach, for example, breaks down the wood fibers and can result in permanent damage to your deck or harm to the surrounding environment. To maintain your wood deck's good looks, reapply sealer or stain about every one to two years. Use these cleaning methods to tackle some of the most common deck stains.

Barbecue Stains (Including Grease and Sauce)

If your last backyard barbecue got messy, remove grease spots or saucy spills using a household dish detergent that's designed to cut through grease, such as Dawn Ultra Liquid Dish Soap ($3, Target). Using a stiff-bristled brush ($8, The Home Depot), scrub the area with a mixture of detergent and hot water. Use a dampened sponge to mop up the loosened grease. Rinse the area with a garden hose before it dries.

Candle Wax

To clear away wax drips from outdoor candles, first carefully scrape away as much residue as possible using a credit card, putty knife, or similar tool that will not gouge the wood. Cover the area with plain paper (such as a brown paper bag) and use an iron set on low to gently warm the wax. The residue should lift away on the paper. Repeat until the wax is gone, replacing the paper as needed. Alternatively, you can clean candle wax off a wood deck using mineral spirits ($7, The Home Depot). Saturate a rag and set it on the dried wax until it absorbs the residue, rubbing lightly if necessary.

Green Algae or Moss

Spurred on by damp, dark conditions, algae and moss growth creates a slippery deck surface and can lead to wood rot or other permanent damage. These stains are difficult to remove and usually reappear once the roots are formed in the wood, so it's important to treat them right away. Remove green algae or moss stains on wood decks using an oxygen bleach solution. Mix together one cup oxygen bleach, 1/2 cup borax, and 2 tablespoons dish detergent in one gallon water. Scrub the stained areas with a brush dipped into the solution, then wait about 15 minutes before rinsing with a hose.

Leaf Stains

When leaves accumulate on decks or porches, they can start to decompose and leave behind dark marks or silhouettes. To remove leaf stains on wood decks, scrub the area with a solution of dish detergent and warm water. Let the cleaning solution soak in for about 15 minutes before scrubbing again and rinsing with a hose. For stubborn stains, try scrubbing with a solution of one cup oxygen bleach ($9, Target) to one gallon of water, repeating as necessary until the stains disappear. You can avoid these stains by regularly clearing away leaves from your deck as they begin to fall.

Mildew or Mold

Mildew or mold is a common problem for decks in shady or damp areas, but regular cleaning can help keep it at bay. Clean the surface with a commercial deck cleaner/brightener ($16, The Home Depot). If it is not in liquid form, mix the powder concentrate with the recommended amount of water and apply with a garden sprayer, brush, or roller. Wait several minutes, then brush briskly with a stiff brush or broom. Rinse with a garden hose. Some deck cleaners contain acids or chlorine, which can harm plants; check the label before using the product.

Rust

Rusty outdoor furniture can leave red-brown rings or marks on your deck. To remove rust stains, spray a 50-50 solution of water and distilled white vinegar on the stain and let sit for about 10 minutes before wiping clean. For stubborn stains, try using an oxalic acid cleaner ($10, The Home Depot) following the manufacturer's instructions.

Tannin Stains

Tannins are naturally occurring compounds found in many trees and plants. They can sometimes cause dark stains to appear on wood decks after rain draws tannins to the surface. Remove the black streaks of tannin-rich woods with a specially formulated deck cleaner for tannin stains ($10, The Home Depot), following the manufacturer's instructions.

Tree Sap

Tree sap can harden on the surface of your deck, creating stains that are difficult to remove. To soften the sticky residue, apply Murphy Oil Soap ($3, Walmart) directly on the stain. Let sit for about 15 minutes, then scrub with a brush and rinse.

outdoor living space with sectional and porch swing
Credit: Jason Donnelly

How to Remove Stains on Stone or Cement Patios

Brick pavers, cement surfaces, and flagstones create sturdy patios that stand up well over time, but they can be prone to certain stains. Follow these instructions to remove stains from your stone or cement patio.

Candle Wax or Paint

Remove all the paint or wax you can with a putty knife ($1, The Home Depot). Scrub the area with a metal-bristled brush and cold water. If this fails, apply mineral spirits to the area. If the candle wax stain is on concrete and these treatments don't work, try covering the area with plain paper and warming it gently with an iron set on low. When you lift up the paper, the waxy residue should come with it. Replace the paper as needed until the wax is gone. For paint stains on concrete, try applying a paint stripper ($20, The Home Depot) according to the manufacturer's instructions.

Dirt and Grime

Cleaning dirt and grime off a stone or cement patio often requires only water and some scrubbing. Simply hose down the surface with water and scrub it with a stiff broom. If this doesn't work, mix dishwashing detergent or trisodium phosphate ($4, The Home Depot) with warm water and go over the area with a stiff brush or broom. Rinse with a hose.

Efflorescence

Efflorescence refers to a white haze that sometimes appears on concrete or paver patios shortly after installation. It occurs naturally as salts within the stone migrate to the surface. To remove efflorescence from your patio, start by rubbing the area with a wire brush. If this doesn't work, many commercial efflorescence removal mixtures ($26, The Home Depot) are available that will remove the stain. These typically contain acid, so be sure to wear gloves and safety glasses.

Grease Stains (Including Food, Oil, or Lipstick)

To remove grease stains on a patio, mix dishwashing detergent in warm water. Work the mixture into the stain with a stiff brush or broom and rinse with clean water. If this doesn't work, add ammonia to the detergent and water mixture, following the same rinsing procedures, or scrub well with mineral spirits.

Protein-Based Stains (Including Blood, Coffee, Juice, or Feces)

Remove protein-based stains from your patio as soon as possible using a solution of dishwashing detergent and cold water. Work with a stiff brush or broom, and flood the area with the detergent mixture. Rinse with clean, cold water.

Soot

Soot left behind from bonfires can leave black marks on your patio. To remove these stains, clean the area with a detergent and water solution. If this doesn't work, apply a mixture of equal parts muriatic acid ($10, Lowe's) and water. Be sure to wear gloves and protective eyewear.

Tar and Heel Marks

Try dishwashing detergent in warm water to remove patio stains from tar or heel marks. If you're unsuccessful, scour the area with a stiff-bristled brush and mineral spirits. Don't use a scouring pad. If some residue remains, flood the area with mineral spirits and blot it up with a soft absorbent cloth, repeating as necessary until the stain is gone.

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