How To Properly Prep A Garage Floor For Concrete Coatings

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No matter how hard we try, we cannot invent a successful coating that does not require proper preparation.

Properly prepping a floor will help provide a smoother surface as well as ensure a strong bond between the coating and the concrete. Most of the time when a coating application fails, it’s due to inadequate prep work. Let’s go over how to properly prep a concrete floor for coatings and what methods can be used.

Diamond Grinding

Diamond grinding involves the rotation of disks/stones fitted with diamond cutting grain. Depending on the amount of disks/stones used, you can achieve looks from 60 grit sandpaper to a highly polished concrete floor. When you diamond grind a floor, you not only smooth out the surface and open its pores, but you remove any stains and built up debris.

To determine what diamonds to use, you need to test the hardness of the concrete. Hard concrete is going to require softer diamonds and softer concrete will require harder diamonds. While diamond grinding, it is imperative you overlap and walk the grinder to prevent track marks. Keeping the grinder moving by pushing it side to side as you walk will keep the grinder from over grinding one particular area.

Most coatings require the surface to feel like 60-80 grit sandpaper with open pores. This can usually be achieved with 30-grit diamonds. By going higher, you could prevent the primer from absorbing into the substrate properly. This will ultimately cause the coating application to fail.

Diamond grinders are in fact grinding the concrete, so they can create quite the mess. Using OSHA approved vacuums with HEPA filters during grinding help minimize dust. Having a clean surface is extremely important for your safety and for the application process as you do not want any dust or debris on the surface. Excess debris on the surface can prevent the coating from soaking into the substrate properly, also causing it to fail.

You can also use diamond grinders to remove existing coatings, surface adhesives, mastic and other foreign materials. The removal will allow the base coat to be properly bonded to the concrete. Without removing the existing coatings/foreign materials, the coating will not be able to properly adhere to the concrete.

Shot Blasting

Another common (but unfavored) method used to prep a concrete floor for coatings is shot blasting. Shot blasting works by using an airless, centrifugal wheel that propels beads at a high velocity in a controlled pattern and direction. When shot blasting, it’s required to overlap areas and this causes blast lines.

This method, however, is not as favored as diamond grinding even though it is more affordable. Even the most careful technicians can cause pits and divots in the floor from shot blasting. If your intent is to apply a thin layer of coatings over the concrete, shot blasting should not be your preparation method. This is because all of the imperfections caused by the shot blaster will show through the coatings.

Acid Etching

Another popular method of preparation is acid etching. This method consists of applying hydrochloric or phosphoric acid and then washing it away with water. Although this method used to be very common, it has lost its popularity over the years. In fact, many contractors advise against acid etching for numerous reasons; let us break those down for you.

Aside from plastics, hydrochloric acid eats through anything it touches including clothing and skin. This can be very dangerous for the individual applying the acid as it will cause a chemical upon contact. Another risk of handling these products is inhaling harmful fumes. These risks can occur even when wearing safety gear and equipment.

The acid not only eats through skin and clothing, but it can also damage the concrete. The acid breaks the balance between alkaline pH and the other materials that provide concrete its hardness and durability. If over-etching occurs, it can cause erosion which is going to weaken the structure of the concrete.

Acid etching is also extremely harmful to the environment. After the acid has been applied and the etching process has taken place, the slab is rinsed with water. The water is meant to neutralize the solution. Many local and federal agencies have restrictions on washing acid solutions down drains as they pose a major risk to waterways and the environment.

Another downside of acid etching is its inconstancy. Acid etching doesn’t have the ability to remove existing coatings or other contaminants like oil or other water-insoluble materials. This will prevent the coating from adhering to the concrete properly, inevitably causing it to fail.

What is the best method of preparation for concrete coatings?

After weighing out our options, it is safe to say diamond grinding is the best preparation method for concrete coatings. Whether you’re applying polyurea/polyaspartic coatings or epoxy, your best option is going to be diamond grinding. It is not only the safest way to prep the surface, but it is the most effective and provides the best results.

Here at TAGG Concrete Coatings, we take our install process very seriously. You will never have to be worried if your surface was prepped properly when hiring our company. Not only do we use the best products available, but we always properly prep each surface. Pairing the best products in the industry with a proper preparation method allows us to confidently provide our customers with a 15 year warranty on all residential applications. If you are in North Carolina, give us a call today or fill out our inquiry form on our website to schedule your free on-site estimate.