Proper garage floor preparation is crucial for a long lasting garage floor coating system. Before installing any coating to your garage floor, it must first be clean of dirt, oil, and previous sealers. First scrub the floor with a degreasing detergent and a power scrubber if available. Otherwise, a stiff broom and pressure washer will work well. Professional installers use floor grinders to profile the surface, but the do-it-yourself homeowner can accomplish satisfactory results washing the floor with a Muriatic Acid Bath. Use a solution of four parts water to one part muratic acid, followed by neutralizing the surface with a solution of one part ammonia to ten parts water. Work the acid solution into the surface with a stiff-bristled brush then do the same with the neutralizer and rinse with a high-powered washer. I’ve found that muriatic acid from a pool supply company is stronger than the pool acid found at Walmart, and big box stores.
Garage Floor Prep Safety Tips
Be sure to use a vapor respirator approved for use with muriatic acid. Muriatic acid vapors can actually burn your lung linings. Safety goggles, old clothes, rubber boots (if available), and gloves should also be worn when working with acid. As a precaution, add the acid to the water when diluting to the correct ratio. This reduces the chance of splashing concentrated out of the bucket. Be sure the area is well ventilated and the garage doors are left open. A few fans can help to circulate the air reducing noxious fumes and speeding the drying time of the concrete garage floor.
Preparing and Repairing Garage Floor Cracks
Any cracks in the garage floor must be dealt with prior to installing your garage floor covering. Small hairline cracks can simply be filled with an 100% solids epoxy paste, then scraped or sanded flush with the floor. Large cracks could be filled with sand leaving 1/4″ to top with 100% solids epoxy. Spalls or other imperfections should be overfilled using 100% solids epoxy or a fast-drying cementitious product then ground flush when cured. Tooled control joints are there for a reason and should not be filled. However a thin bead of latex caulk will seal the bottom of the joint providing an easy to clean floor. Smaller saw cut expansion joints make be filled with a Polyurethane Concrete Sealant.
Testing your Garage Floor for Moisture
After your floor thoroughly dries, you must test to see if you have water vapor transmission. If moisture is coming up through the concrete slab, your garage floor coating will not bond and end up bubbling or peeling off. To determine if there is moisture, simply cut a square 2 ft. by 2 ft. piece of plastic sheeting and tape all edges of the plastic sheeting to your floor. Wait 24- 48 hrs and then check to see if water collects on the underside of the plastic. If moisture is present, you have moisture vapor transmission and a good vapor barrier will need to be put down before the primer coat. Products such as Pene-Krete are recommended for this application. More about Garage Floor Moisture Testing Methods here.