· by Michael Blair, Nashville's Garage Floor
A garage floor coating either bonds to the concrete or it does not, and that is settled by preparation. Products get blamed for failures that were determined before anything was opened.
The concrete has to be profiled
A troweled garage slab is dense and closed. Coatings need a surface profile — mechanical grinding or shot blasting — to key into.
Acid etching, which most DIY kits supply, produces a far weaker profile and is the single most common reason a kit peels within a year or two.
Moisture is the other half
Slabs release moisture upward, and Middle Tennessee slabs on grade with no vapor barrier beneath do it indefinitely. Vapor pressure under an impermeable coating breaks the bond.
A moisture test before coating is not optional. Plastic sheet taped down for a couple of days is a rough screen; a calcium chloride or in-situ RH test gives a number.
- Mechanically grind or shot blast, do not just acid etch
- Test the slab for moisture before choosing a product
- Repair cracks and spalls before coating
- Remove all oil contamination — coatings will not bond to it
- Respect recoat windows and cure times exactly
Oil contamination
Old oil soaks in and no coating bonds over it. Degreasing removes the surface; grinding removes the contaminated layer, which is why grinding matters twice over.
A patch that peels in the same spot each time is almost always a spot where a car leaked for years.
Hot tire pickup
Warm tires soften some coatings and lift them when the car is parked, which shows as circular patches missing where the wheels sit.
It is a symptom of a weak bond or an unsuitable product rather than an unavoidable fact — properly prepared and correctly specified floors do not do it.