The System

A coating is only as waterproof as its least continuous point. That is worth sitting with, because it explains nearly every garage floor complaint we hear.

A film that stops at the wall line leaves an open joint at the base of the wall — the exact place snowmelt runs to. A crack that was caulked rather than rebuilt is a moving seam under a rigid film. An unsealed door threshold is an open edge pointed at the weather. And a slab that is quietly passing vapor from below is pushing on the bond across the entire floor at once.

So the system is designed around continuity rather than around a single product. Concrete Mender makes the cracks part of the slab again. OR-621 is applied into an open CSP 3–5 profile so the bond is mechanical and the build is thick enough to be a barrier rather than a skin. OR-55 seals it as a single surface, coved up the wall base and carried cleanly to the threshold. No seams, no terminations pointed the wrong way.

If you take one thing from this page, take this: test the slab before you buy material.

ASTM F1869 (anhydrous calcium chloride) measures how much moisture vapor is coming out of the top of the slab, reported in pounds per 1,000 square feet per 24 hours. It is quick, cheap, and reads the surface zone.

ASTM F2170 drills in-situ probes and reads relative humidity at depth inside the slab. On slab-on-grade garages it is the more reliable predictor, because it sees what the concrete is holding rather than what happened to be evaporating on test day.

Older garages, garages built over a compromised or missing vapor retarder, and any garage cut into a hillside are the usual offenders. High readings do not mean you cannot coat the floor — they mean the primer and build have to be specified for the number. What you cannot do is guess, install, and find out in March.

A practical field check while you wait on results: tape a 2 ft square of clear plastic to the slab, seal all four edges, and leave it 24 hours. Condensation under the plastic or a dark patch on the concrete means moisture is moving. It is not a substitute for a test, but it will tell you whether to expect one.

Grinding. Diamond grind or shot blast to CSP 3–5. Everything comes off: old floor paint, cure-and-seal from the original pour, tire marks, and the polished laitance on a troweled slab. Acid etching is not adequate for a hard-troweled garage slab — it does not produce a consistent profile and it leaves residue behind.

Oil. Garages are the worst substrate for contamination because decades of drips have soaked into the concrete. Degrease before grinding, not after, or you will drive the oil into the fresh profile. Deep stains sometimes need to be ground out entirely.

Cracks and spalls. Repaired with Concrete Mender before profiling. It penetrates the concrete surrounding the defect and cures into it, so the repaired area behaves like slab under a wheel rather than like a strip of filler. Control joints in a garage are typically filled and coated through, so the finished floor reads as one surface.

Perimeter and threshold. The system is coved up the wall base 4–6 inches and terminated at the door threshold with a clean, sealed edge. This is the difference between a floor that is coated and a floor that is waterproof: meltwater running off a vehicle finds the perimeter first.