Painting concrete floors can transform your space. However, for the best results, proper preparation is essential. This includes cleaning, abrading and thinning the first coat. Skipping these steps can lead to poor adhesion, peeling and paint delamination. In this article, we’ll explain why cleaning and preparing your concrete floor before painting is important and how to prepare a concrete floor for painting.
Why Clean and Prepare Concrete Floors Before Painting?
Painting concrete floors can feel like a big task. When you’re eager to get the job done, it can be tempting to skip the cleaning and preparation steps. However, you shouldn’t overlook the importance of cleaning and preparing before painting concrete floors. This process will:
- Ensure proper paint adhesion to the surface
- Prevent peeling, cracking and bubbling
- Remove dirt, debris, grease and other contaminants
- Improve the paint’s intercoat adhesion
- Result in a long-lasting and durable finish
Rushing the job may save time now, but it can ultimately lead to poor adhesion and a failed paint job later.
What Happens if You Skip Concrete Floor Preparation?
Here’s a real-world example of what can go wrong when you don’t clean and prepare your surface before painting concrete floors. In this case, the paint used was our Two Pack Epoxy Non Slip BS 08 E 51 Yellow. This is a heavy-duty concrete floor paint, designed for high-traffic areas.
The floor wasn’t abraded or cleaned with a concrete cleaner (descaling acid) before painting. On top of that, the first coat wasn’t thinned by 20% as we usually recommend on bare concrete. Thinning the first coat is especially important for bare concrete because it helps the paint impregnate the concrete.
So what was the outcome?
Because the concrete floor wasn’t cleaned or abraded before painting, the paint didn’t adhere properly. This led to paint delamination, which is the separation of the first coat of paint from the concrete. We can see this, as the paint started peeling off in large chunks.
Take a look at the images above. The bright yellow paint is the top layer, while the darker, dirtier side is the underside of the flaking paint. You can clearly see that the paint has adhered to the dirt, not the concrete. If the floor had been properly cleaned and abraded, the paint would have bonded to the concrete instead.
How to Prepare a Concrete Floor for Painting:
The Role of Abrading the Concrete Surface
To prepare a concrete floor for painting, you should first abrade the surface. Abrading roughens the concrete surface by physically sanding it down with tools, such as a mechanical floor sander or a concrete grinder. If your concrete surface is smooth or power floated, it will need to be abraded, as paint will not adhere to smooth surfaces. By roughing up the surface, it allows the paint to impregnate the concrete, creating a better bond. Abrading also helps to remove any surface-level contamination, including dirt.
If you’re painting over existing concrete floor paint, it’s important to first check compatibility between the two paints. After confirming this, the existing coating should be lightly abraded to provide good intercoat adhesion.
How to Clean a Concrete Floor
After you’ve abraded your concrete floor, it’s vital to clean next. Essentially, you want to start with a clean base to achieve the best results. To clean a concrete floor, start by simply sweeping or vacuuming any loose dirt, dust and debris.
If the concrete is extremely dirty or old the most important step is to use a concrete cleaner, such as descaling acid. Descaling acid effectively breaks down mineral salts, oils, dirt and other contaminants on your floor. Without this, contaminants may cause a reaction with the paint, making it bubble or pickle, resulting in loss of adhesion of your concrete floor paint.
When handling this solution, always follow the manufacturer’s guidelines. Make sure to wear safety gear, such as gloves and eye protection and ventilate the area.
Why You Should Thin the First Coat of Concrete Floor Paint
Thinning the first coat by 20% with the appropriate thinners helps the paint soak into the porous concrete. This creates a stronger bond and a solid base for additional coats. Without thinning, the paint may sit on the surface rather than penetrating it, leading to potential paint delamination and peeling. Thinning the first coat can also act as a primer or sealer.
Concrete Floor Paint at Black Country Paints
At BC Paints, we are leading manufacturers, providing a range of high-quality concrete floor paints designed for durability and long-lasting performance.
With 30 years of experience in manufacturing and supplying professional-grade coatings, we ensure quick lead times and nationwide delivery. Contact us today to find your ideal concrete floor paint for your needs and get expert advice on achieving the best results.
