How to Repair Concrete
Learn how to prevent cracking, erosion, spalling, staining, and corrosion with the right concrete sealants. Harden and protect concrete surfaces, and make old concrete look new again.
Despite its durability, concrete is a porous material that can absorb water, chlorides, stains, and other water- or oil-based materials. Over time, unprotected concrete will deteriorate from moisture damage. If you do not protect your concrete surface, you may see cracking, erosion, spalling, or stress fractures from freezing and thawing, staining, or corrosion of steel reinforcement bars. Waterproof concrete sealers harden and protect concrete surfaces. They can also make old concrete look new again.
Prepare the Concrete Surface
The first step in protecting a concrete surface is to use a solvent cleaner. A solvent etches, cleans, and degreases the surface. This will help maximize the adhesion and durability of the sealer you select.
Follow these steps to clean concrete:
- Apply the cleaner to the concrete surface.
- Scrub the concrete surface using a brush or a pressure washer.
- Rinse concrete with water.
- Allow to dry thoroughly before applying concrete sealant.
Concrete Sealers and Paint
Masonry Water proofers
Select a Concrete Sealer
The type of sealer to apply depends on the project. You should consider whether the surface is interior or exterior, the amount of exposure to the sun, the amount of traffic, and whether you prefer a color or clear finish.
There are four basic types of sealers for concrete surfaces:
- Epoxy Sealers: Because they are not UV-resistant, epoxy products are best for interior spaces such as garage floors and carports.
- Concrete Sealers: Concrete sealers and paint make old concrete look new with a low-gloss protective finish.
- Masonry Water proofers: Available in latex- and oil-based formulas, masonry water proofers may be used on concrete, stucco, brick, and cinder block.
- Clear Finish Sealers: Clear finish sealers waterproof the surface without changing its appearance.
Concrete Repair Safety Procedures
To ensure a safe project while repairing or sealing concrete, make sure to read all product label information, including precautions, warnings, and instructions before use. Follow all label directions.
Proper ventilation is essential when applying sealers. Be sure to use a dust mask or respirator.
Apply Concrete Sealer
You can apply concrete sealers with a paintbrush, conventional roller, garden sprayer, or airless sprayer. When choosing the method to apply the sealer, consider the size of the project and the amount of time you want to spend.
- Apply a test application to a small area of concrete to make sure the result is what you want.
- After cleaning the concrete surface, apply a thin coat of the sealant to the surface evenly. Some more porous surfaces may require a second coat. Allow eight hours before applying a second coat.
- Avoid excessive brushing or rolling of the concrete sealer. Brush out any puddles.
- Rinse tools and any surrounding surfaces with soap and water before the material hardens. You can remove dry sealer with paint thinner.
Q and A: Answers to the Most Frequently Asked Questions about Sealing and Repairing Concrete
How often should a concrete sealer be applied to a concrete surface?
This will depend on the amount of traffic on the concrete and the exposure to the sun and chemicals. Generally, concrete surfaces should be prepped and sealed at least every two years.
Can a concrete sealer be applied without cleaning the surface of the concrete?
Yes. However, cleaning the concrete surface will ensure maximum adhesion and durability of the sealer.
How long does the concrete sealer have to dry before it's exposed to rain?
Sealers usually dry in one to two hours, depending on the temperature and humidity. It should not be exposed to rain for 24 hours or at least until it has dried.
How soon can new concrete be waterproofed?
Concrete takes 28 days to cure. Therefore, best results are obtained by treating the concrete with waterproof sealant after 28 days.
Can it be too hot or too cold to apply a concrete sealer?
Yes. It is best to apply sealers when temperatures are between 40°F and 100°F.
How much cleaner and concrete sealant do I need?
Use the chart below to determine how much cleaner and concrete sealant your project will require.
Square Foot Coverage
Other Supplies You May Need for Preparing and Sealing Concrete Surfaces in your Home or on your Farm
- Concrete cleaner
- Cleaning brush
- Brush applicator
- Paint brush
- Conventional roller (½" nap)
- Sprayer (Garden or Airless)
- Protective gloves
- Paint thinner
- Additional hose (if desired)
- Dust mask or respirator