Having a beautiful concrete patio is a great way to extend your living space outdoors. However, over time concrete can become stained from things like leaves, dirt, oil, food and drink spills, mold and mildew. While some stains will wear away with time and weather, others can be difficult to remove. Removing stains and restoring the look of your concrete patio requires using the right techniques and products. This comprehensive guide will provide tips on how to remove some of the most common stains from concrete patios.
Causes of Stains on Concrete Patios
There are several factors that can lead to staining on outdoor concrete surfaces like patios. Being aware of these potential causes can help you prevent stains or treat them promptly when they occur:
- Organic materials like leaves, grass, dirt and pollen that contain tannins, acids and other chemicals that can alter the color of the concrete. These tend to leave brown, black or orange stains.
- Food and drink spills containing sugars, oils or acidic ingredients like citrus juices, alcohol, etc. These can soak into the pores of the concrete and cause dark stains. Foods like ketchup, barbecue sauce, wine, and salad dressings often lead to stubborn staining.
- Mold, mildew and algae growth resulting from moisture buildup. This leaves black, green or red discoloration. Damp, shaded areas of the patio are especially prone to these types of biological stains.
- Weathering over time including exposure to the sun, rain and freeze/thaw cycles. This can cause fading, pitting and rough patches on the concrete surface. Road salt used in winter can also etch and stain concrete.
- Oil and grease stains from automobiles, cooking equipment and other sources. These tend to leave dark black stains. Oil drips from cars, grease from grills, and cooking oils are common culprits.
- Hard water deposits containing minerals that leave white stains on concrete. These stains are caused by mineral elements like calcium, magnesium and lime that are found in hard water.
- Chemical spills from cleaners, paints and other substances. These can etch and discolor concrete. Products like ammonia, bleach, paint removers and battery acids can all damage concrete surfaces.
Tips for Removing Different Types of Stains
Here are some tips on how to remove some of the most stubborn stains from outdoor concrete patios:
Organic Stains
Baking soda paste – Mix together baking soda and water to make a thick paste. Spread the paste over the stained area using a stiff scrub brush or broom. Allow it to sit for several hours, or even overnight if the stain is especially stubborn. The baking soda will help draw out the stain. After letting it sit, scrub the area with the brush then rinse away using a garden hose.
Oxygen bleach cleaner – Oxygen bleach products, such as OxiClean, break down organic stains safely without the harshness of chlorine bleach. Make a concentrated solution by mixing the oxygen bleach powder with warm water. Use a stiff bristle brush to work it into the stain. Allow it to sit for 10-15 minutes before rinsing thoroughly.
Poultice – To pull out really stubborn organic stains, make a poultice by mixing a tablespoon of chlorine bleach or oxygen bleach into a cup of talcum powder. Add just enough water to make a thick paste. Trowel the poultice over the stain, covering it with a layer about 1/4 inch thick. Cover with plastic wrap or a plastic bag, sealing the edges with duct tape. Allow the poultice to sit for 24-48 hours, re-wetting it if it dries out. Scrape off the poultice and rinse the concrete thoroughly. Repeat as needed for tough stains.
Oil and Grease Stains
Degreasing cleaner – Specialty degreasing concrete cleaners, such as Simple Green Concrete Cleaner or Krud Kutter, work well on oil and grease stains. Spray or scrub the cleaner directly onto the stain. For larger stains, let the cleaner soak for 10-15 minutes before scrubbing with a stiff bristle brush. Rinse thoroughly with water.
Cat litter or absorbent – Pour cat litter, grease fighting absorbent or automotive absorbent directly onto the grease stain. Let it sit for several hours to soak up the oil or grease. Sweep up the absorbent and discard. Scrub the remaining stain with degreasing cleaner and rinse.
Citrus cleaner – As a more eco-friendly option, use a concentrated citrus cleaner made for concrete. The citrus oils help break down grease stains. Scrub it in and let it sit for 10-15 minutes before rinsing.
Drink and Food Stains
Baking soda paste – For wine, coffee, juice, ketchup or berry stains, make a paste of baking soda and water. Use a stiff scrub brush to work the paste into the stain, allowing it to sit for 2-3 hours. The baking soda will help draw out and neutralize the stain. Rinse clean.
Sodium carbonate and water poultice – Mix 2 parts sodium carbonate (washing soda) with 1 part water to make a thick solution. Apply to the stain, covering with plastic wrap. Let sit for 24 hours before rinsing thoroughly. This can help lift out sugars and acids from drink stains.
Concrete stain removers – Look for concrete stain remover products that contain powerful surfactants, detergents and/or oxalic acid to penetrate and lift out stubborn food and drink stains. Carefully follow label directions.
Mold and Mildew Stains
Bleach solution – Mix 1 part regular chlorine bleach with 4 parts water in a spray bottle. Spray the solution liberally onto mold stains. Let it soak in for 10-15 minutes before scrubbing and rinsing. Allow the concrete to dry fully in direct sunlight.
Hydrogen peroxide solution – As a more eco-friendly alternative, use a 50/50 mixture of hydrogen peroxide and water. Spray or scrub onto mold stains and let sit briefly before rinsing. The hydrogen peroxide will kill mold spores on contact.
** Commercial mold removers** – Look for concrete mold stain removers that contain sodium hypochlorite, bleach and detergents formulated to kill mold and lift stains. Various brands include Wet & Forget, Moldex and StoneTech Mold & Mildew Stain Remover.
Hard Water Stains
Muriatic acid – Carefully follow product directions to dilute muriatic (hydrochloric) acid with 10 parts water. Use protective gear to apply the solution to the stained area using a stiff scrub brush or broom. Let it sit briefly before rinsing thoroughly. Neutralize rinsed water with baking soda.
White vinegar – As a safer and weaker acid, white vinegar can also help break down mineral deposits from hard water. Scrub concentrated vinegar into stains before rinsing. It may take several applications.
Commercial hard water stain removers – Look for removers formulated for concrete that contain acids like sulfamic acid to dissolve mineral stains. Brands like CL-ECO Concrete Stain Remover or Savogran Hard Water Stain Remover can save time scrubbing.
Choosing the Right Concrete Patio Cleaning Products
Having the right cleaners on hand is important for treating concrete stains. Here are some recommended products:
- Oxygen bleach cleaner – Helps break down organic stains. More eco-friendly than chlorine bleach. Example brands include OxiClean, CLR Oxygen Bleach, or Rejuvenate Oxygen Bleach.
- Sodium carbonate – Also called washing soda, it helps lift food, oil and drink stains. Arm & Hammer Super Washing Soda is a widely available brand.
- Citrus cleaner – Made from citrus oils, it breaks down grease stains. Try products like CitraSolv Natural Citrus Cleaner or Sunshine Maker Citrus Cleaner.
- Chlorine bleach – Helps remove mold, mildew and tough organic stains. Just be sure to dilute with water first.
- Muriatic acid – Diluted, it removes hard water and mineral deposits. Must be handled with extreme care by wearing gloves and eye protection.
- White vinegar – A mild acid that helps break down mineral deposits as a more natural alternative to muriatic acid. Any white vinegar will work.
- Baking soda – A mild abrasive that creates a stain-lifting paste. Arm & Hammer and other brands of common baking soda can be used.
- Liquid dish detergent – Added to baking soda pastes, it helps emulsify oil-based stains on concrete. Brands like Dawn work well.
- Pressure washer – Helps provide the abrasion needed to remove tough stains and can be used to rinse away cleaning solutions. Electric pressure washers start around $100 for light duty models.
Tips for Applying Concrete Patio Cleaners
When using cleaners and chemicals on concrete, it’s important to take safety precautions:
- Always read labels and follow instructions carefully. Use gloves and eye protection whenever handling chemicals.
- Wet down the concrete first to keep chemical solutions from absorbing too quickly which can lead to etching or discoloration.
- Apply cleaners during cooler temperatures without direct sun to prevent rapid evaporation.
- Limit the amount of time cleaners sit; rinse thoroughly and do not let solutions dry on the concrete.
- Use only as much pressure needed when scrubbing to avoid damaging the concrete surface. Avoid wire brushes.
- Rinse with a pressure washer if possible or a steady stream from a hose. Soak up excess water to prevent pooling.
- Neutralize and safely dispose of used cleaners, especially acids like muriatic acid, as recommended.
- Allow concrete to dry fully before using again; sunlight accelerates drying time.
Tips for Preventing Future Concrete Patio Stains
The best way to keep your concrete patio looking clean is by preventing stains in the first place through good maintenance:
- Sweep frequently to remove dirt, leaves and other debris before they get ground in.
- Rinse off spills immediately before they have a chance to soak into the concrete. Absorb wet spills with towels.
- Apply penetrating concrete sealers to protect the surface; reseal every 1-2 years depending on wear. Sealers can make future stains easier to clean.
- Check for areas where water accumulates and improve drainage as needed. Eliminate standing water to prevent biological stains.
- Remove outdoor furniture, grills, and accessories when not in use to prevent rust stains.
- Use outdoor mats in high traffic areas to keep soil, sand and abrasives off the patio surface.
- Keep barbecue grills and turkey fryers on metal trays or grill mats to catch grease drips. Dispose of grease properly.
- Avoid dragging planters, furniture legs or other hard objects across the concrete that can scratch the surface making it more stain prone. Lift don’t drag.
- Use lawn fertilizer and weed killer carefully to avoid overspray drifting onto the patio. Spot treat weeds instead of spraying everything.
When to Call a Professional Concrete Cleaning Service
For badly stained outdoor concrete surfaces, especially intricate stamped or stained concrete, consider hiring professional concrete cleaners. Look for licensed services experienced in safely handling harsh concrete cleaners and pressure washing correctly. Professionals have access to equipment like:
- Powerful 3000+ PSI pressure washers
- Truck-mounted cleaning systems
- Industrial strength degreasers and stain removers
- Professional grade muriatic acid and rust removers
- Specialized tools for cleaning textured concrete
Professionals can assess your concrete patio’s staining issues and match the right methods and products for the job. For severe staining or etching that requires grinding or resurfacing, professionals have the proper tools.
Maintaining a Clean Concrete Patio
By using the right cleaning techniques and products, you can successfully remove stains that may develop on your outdoor concrete surfaces. Taking steps to protect the concrete and prevent future stains will go a long way in keeping your patio looking pristine. Address stains promptly before they have a chance to set into the concrete. With periodic maintenance and cleaning, you can enjoy your beautiful concrete patio for many years.
