Why Your Concrete Garage Floor Is Discolored and How to Fix It

Kathryn Pomroy
Written by Kathryn Pomroy
Updated September 23, 2021
Interior garage
Allison - stock.adobe.com

You can fix a discolored garage floor in a few easy steps

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Despite the durability of concrete floors, you may have noticed imperfections, stains, and concrete discoloration showing up over time. Discoloration can happen thanks to a variety of factors, including age and mistakes in installation. Luckily, it can be fairly easy to pin down the reason for concrete discoloration and implement a fix.

Why Concrete Garage Floors Can Get Discolored

When a pro first installed your concrete garage floor, it was smooth, shiny, and all the same color. Now it’s blotchy and discolored. There are several reasons why this may have happened.

Time Since Installation

Garage floors can take up to five months to fully cure, so if you have a fairly new garage floor with discoloration, you may want to give it a bit more time to settle in first.

Inconsistency in Materials

The concrete for your garage floor should be mixed at the same proportions to create a consistent look. Sometimes, if the floor is installed across many days or even at different times during the day, your floor may appear blotchy, thanks to varying proportions or temperature changes. 

If you’re still in the process of getting a new garage floor, make sure 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.

Problems at the Job Site

Sometimes mixing concrete on-site can cause the surface of your garage floor 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 can have an effect. 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 can all cause discoloration too.

Good concrete garage slabs 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 garage floor is smooth, durable, and spotless.

Using Recycled Cement-Like Materials

Many turn to sustainable ways to get a job done, and laying a concrete garage floor or upgrading existing concrete floors is no different. 

But you might run into 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 cement garage floor, you may see areas of discoloration as it mixes with your existing floor materials.

How to Fix Your Discolored Concrete Garage Floor

Sometimes you just end up with discolored concrete no matter how vigilant you are. Luckily, there are common fixes that you can do yourself to remove the stain from your garage floors or hire a pro to do the work.

1. Hot Water Can Remove Some Discoloration

If your concrete floor 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.

2. Color Staining Can Give Your Garage Floor a New Look

Adding a tint of color to discolorations can camouflage imperfections and give your space a whole new look. Concrete stains cost $50 to $225 or $0.20 to $0.85 per square foot, not including the protective topcoat.

3. Acid Treatments Can Take on Major Discoloration

If your concrete garage floor 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. Be sure to leave the garage door open for ventilation and only use this solution in small doses.

4. Apply a Thin Polymer Coating to Make Discoloration Disappear

Often used to hide graffiti, you can apply a thin polymer-modified coating to hide dislocations and stains on your concrete floor—a 50-pound bag costs about $20 at your local hardware store.

5. Concrete Garage Floor Paint Is an Affordable Option

Essentially a tougher version of interior wall paint, concrete garage 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.

Garage floor paint costs about $40 or $0.15 per square foot.

Remember, when hiring a local concrete company, be sure to get quotes from multiple pros, look for contractors who are licensed, insured and bonded, and who have great reviews.

How to Prevent Concrete Discoloration

To prevent discolored concrete before you even get a new garage floor, it pays to find a concrete contractor that provides quality work in your area.  Ask these questions:

  • Do you use materials that comply with American Society for Testing and Materials (ASTM) standards?

  • If necessary, will you adjust to changes in weather?

  • How will you lay the subgrade so that 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?

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