DIY Surface Preparation Guide — How to Prepare a Concrete Floor for Polyurea Garage Floor Coatings

SURFACE PREPARATION is the key element for long term success. The concrete surface must allow the coating to absorb into the surface of the concrete to create a strong mechanical bond. Although this guide is written for Polyurea floors, the contents are also applicable to epoxy floors. Some variations may exist. For example for epoxy floors, we suggest a primer. IMPORTANT: There are two moisture tests that should be performed. One checks penetration into the concrete and the other checks what is coming out of the concrete

Concrete Surface Profile Etching Vs Grinding

SURFACE PREPARATION:

Acid etching, grinding and light sandblast are acceptable preparation methods. The objective is to prepare the concrete surface to allow the coating to absorb into the concrete providing a strong mechanical bond. The pictures above illustrate the surface profile, an overly aggressive surface profile can telegraph thru on thin mil applications. The higher solids and higher the build of the floor, the more aggressive the surface preparation needs to be. The photo above, from left to right, shows the desired profile after etching, grinding or a light shot blast.

POROSITY TEST:

Once the concrete surface area is completely prepped, dry and clean, spray a small amount of water on the concrete surface to observe if the water immediately begins to absorb into the substrate. If beading or puddling occurs, additional surface preparation is required. Repeat the surface preparation process again. The concrete surface must be clean and completely dry prior to the application of stains, sealers, or other coating materials. See the surface preparation checklist. It is very important that the porosity test be repeated in multiple sections of the garage and over any areas where tire marks or stains may have been present. Surfaces must be clean, sound, dry, and free of oils, grease and other bond inhibiting contamination. Test for Water Vapor Transmission Rate ASTM F1249-13, Standard test method.

SURFACE PREPARATION CHECKLIST:

  • Is the concrete surface clean and dry
  • Has the Water Vapor Transmission Rate been verified
  • Has the surface preparation been completed
  • Check all corners and edges for surface proper preparation
  • Check and remove any oil or existing tire marks from vehicle parking areas
  • Has the water porosity test been verified
  • Does the water immediately soak into the concrete
  • Has all the dust and laitance been cleaned and removed prior to the coating application

Precautions

Moisture vapor emission in the concrete (WVT) to be less than 3-pounds per 1000 sq. ft. for the 24-hour period. Calcium Chloride test ASTM F1249-13 recommended. It should not be applied in direct sunlight or on elevated surface temperatures. Polyurea clear coating is not permeable and may turn opaque or cloudy in exterior application due to ground moisture penetration.

More Information on Acid Etching
More Information on Grinding a Garage Floor