Concrete Discoloration: 4 Causes and How to Fix Them
You can fix a discolored concrete floor or patio in a few easy steps
Discoloration often happens due to inconsistency in materials and installation.
Fix concrete discoloration by cleaning the concrete, staining, painting, or resurfacing it.
Prevent concrete discoloration by using a reputable contractor.
Despite the durability of concrete, you may have noticed imperfections, stains, and concrete discoloration over time. Discoloration can happen thanks to various factors, including age, oil spills, and installation mistakes. Luckily, it can be easy to pinpoint the reason for concrete discoloration and implement a fix. You can have a fresh-looking surface in no time, whether it’s your garage floor, sidewalk, patio, or driveway.
How Does Concrete Discoloration Happen?
When a pro first installed your concrete floor or driveway, it was smooth, shiny, and all the same color. Now, it’s blotchy and discolored. There are several reasons why this may have happened.
1. Time Since Installation
Garage floors, driveways, and concrete floors can take up to five months to cure fully, so if you have fairly new concrete with discoloration, you may want to give it a bit more time to settle in first.
2. Inconsistency in Materials
Concrete mix should have the same proportions across the project to create a consistent look. Sometimes, the floor or sidewalk is installed across many days or even at different times during the day. In that case, your concrete may appear blotchy thanks to varying proportions or temperature changes.
If you’re still in the process of getting new concrete, ensure your contractor only uses materials that comply with American Society for Testing and Materials (ASTM) standards. Also, ask plenty of questions about work consistency when getting your quote and check reviews.
3. Problems at the Job Site
Sometimes, mixing concrete on-site can cause the surface of your concrete to appear blotchy and discolored. In addition to the issues mentioned above, here are a few other factors that can cause discoloration:
Adding calcium chloride to speed up the drying process: If not mixed correctly, it will create discoloration.
Covering a slab with polyethylene sheeting: Discoloring can occur when not all portions of the plastic are in direct contact with concrete.
Lack of sealing, use of poor-quality sealant, or improper application: These can all cause discoloration.
Outdoor concrete slabs, such as garages and driveways, should hold the weight of cars and trucks through all kinds of weather and for many long years with little evidence of cracks or discoloration. Pros should adjust for issues like changes in temperature and drying times to ensure your concrete is smooth, durable, and spotless.
4. Using Recycled Cement-Like Materials
Many turn to sustainable ways to get a job done, and pouring fresh concrete or upgrading existing concrete floors is no different.
But you might encounter problems here because some recycled and natural materials used to make concrete-like materials perform differently than traditional concrete mixes. So, if you used this type of material to replace part of your floor, driveway, or sidewalk, you may see areas of discoloration as it mixes with your existing materials.
How to Fix Discolored Concrete
Sometimes, you just end up with discolored concrete no matter how vigilant you are. Luckily, there are common fixes you can do yourself to clean your driveway to remove stains. Or hire a pro to do the work.
1. Clean the Area With Hot Water
If your concrete is only mildly discolored, you may be able to clean the surface with hot water, then scrub with a stiff brush, and repeat as needed on stubborn areas. A pressure washer with an attachment works best to remove grime, dirt, mildew, and rust from concrete.
2. Stain the Concrete for a New Look
Adding a tint of color to discolorations can camouflage imperfections and give your space a whole new look. Concrete stains cost around $50 to $230 or $0.20 to $0.85 per square foot, not including the protective topcoat.
3. Treat With an Acid Solution
If your concrete is badly discolored, you may want to try mixing up a mild solution of 1% to 3% muriatic acid with water and applying it to the discolored areas. If you’re working on a garage floor or indoor area, leave windows and doors open for ventilation. Only use this solution in small doses when indoors.
4. Apply a Thin Polymer Coating
Often used to hide graffiti, you can apply a thin polymer-modified coating to hide dislocations and stains on your concrete. A 50-pound bag costs about $20 at your local hardware store.
5. Cover With Concrete Paint
Essentially a tougher version of interior wall paint, concrete paint is affordable and easy to apply. However, it is highly susceptible to damage from chemicals and road salt, so it may not be an option in some areas of the country. Plus, you’ll have to reapply a new coat every two years. Concrete paint costs about $40 or $0.15 per square foot.
When hiring a concrete company, get quotes from multiple pros and look for contractors who are licensed, insured, and bonded and who have great reviews.
6. Resurface Your Concrete
To hide concrete discoloration and give your concrete a fresh look, consider resurfacing your porch, garage floor, patio, or sidewalk. After repairing concrete cracks and preparing the surface, pour a thin layer of concrete on top of the existing concrete. You can choose a stamped concrete overlay or keep it the standard color and design. Resurfacing concrete is best left to a local concrete resurfacing pro with the experience and tools to ensure a durable, uniform finish.
The cost of resurfacing concrete runs from $3 to $9 per square foot.
Questions to Ask Your Pro
To prevent discolored concrete, it pays to find a concrete contractor who provides quality work in your area. Ask them these questions:
Do you use materials that comply with ASTM standards?
If necessary, will you adjust to changes in weather?
How will you lay the subgrade so it’s uniform and has a consistent appearance?
Will you perform a test pour to see what the concrete will look like when dry?
Do you use chloride-bearing mixtures or calcium chloride to speed up the drying process?
Approximately how many concrete projects have you completed?
Are you licensed and insured?
Could I speak with two to three homeowners who have used your services?
DIY vs. Hiring a Pro
Pouring a concrete patio, sidewalk, driveway, or garage floor isn’t straightforward. You need to ensure the concrete mixture, temperature, and curing process are controlled and uniform. It’s best to hire a concrete pro who has the tools and experience to ensure a smooth, durable, and uniform finish.
The average cost to hire a concrete contractor is $50 to $100 per hour, depending on the type of work and size of the project.
Kathryn Pomroy contributed to this piece.
Frequently Asked Questions
Concrete discoloration is when some or all of the concrete has a different color than its intended shade. It could be dirty, stained, or have issues from installation, such as improper curing or inconsistent finishing. You can fix concrete discoloration in various ways, such as cleaning the surface, painting it, or resurfacing it. To prevent concrete discoloration, hire a pro who has experience with your type of project, whether it’s a garage floor, patio, or porch.
Yes, concrete discoloration is common, as many factors can cause concrete to turn a different color. Differences in the concrete mix or how it was cured can leave the concrete in a variety of different shades. The best way to prevent concrete discoloration is to hire an experienced concrete pro who ensures a consistent installation process.
Yes, concrete changes color while curing, moving from a dark shade when wet to a lighter shade once dry and fully cured. Wait at least 10 days after pouring the concrete to gauge the color of the final concrete. If the concrete remains dark or discolored after that period, reach out to your concrete contractor with questions.
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