September 2026
Most people call us after they have already picked a color. That is fine. But the floor under your car has been sitting there for twenty or forty years doing things you cannot see, and it gets a vote. A garage slab that looks perfectly ordinary can be soaking wet three inches down, sealed with something nobody remembers applying, or moving a hair every winter along a crack that reopens every spring.
None of that means you cannot coat it. It means somebody has to look before anybody promises. Here is what we look at, in the order we look at it, and what each thing tells us.
Concrete poured on grade passes water vapor upward for its entire life. The ground under it is damp, the air in your garage is drier, and the slab is the membrane in between. If there is a vapor barrier under the pour, that traffic is slow. If there is not, and in a lot of older Alabama garages there is not, it never stops.
Put a sealed coating over a slab doing that, and the moisture has nowhere to go. Pressure builds under the film. Eventually it lifts, usually in a shape that looks like a blister at first and then like somebody peeled a sticker off your floor. Nine times out of ten when we are called to look at a failed coating, this or bad prep is what happened.
How you can check it yourself in an afternoon
Tape a two foot square of clear plastic sheeting to the slab, all four edges sealed with duct tape, and leave it alone overnight. Come back the next morning. Condensation on the underside of the plastic, or a dark patch on the concrete where the plastic sat, means the slab is passing moisture. No change means very little, honestly, because the test is crude, but a positive result is worth knowing before you spend money.
We run a calcium chloride test or a relative humidity probe when the plastic tells us something or when the slab just feels suspicious. The probe reads the humidity inside the concrete rather than at the surface, which is the number that matters. A slab reading high does not disqualify itself. It changes what goes on it, usually to a moisture tolerant primer or a urethane cement system that is built to live with vapor drive.
What is already on the floor
Garage slabs collect history. A builder may have sprayed a cure and seal on the day it was poured. A previous owner may have rolled on a hardware store kit in 2011. Somebody may have parked a mower on it for a decade and fed it oil the whole time.
The water bead test
Pour a cup of water on a few spots around the floor. If it soaks in and darkens the concrete within a minute, the slab is open and porous. If it beads up and sits there, something is sealing it. Sealer is not a problem, it just has to come off, and coming off means grinding rather than a chemical stripper, because strippers leave residue in the pores that then ruins the bond you just paid for.
Oil is more stubborn than sealer
An oil spot that has been there for years is not on the concrete, it is in it, sometimes a quarter inch deep. Grinding takes off the top layer but oil below the cut line will keep migrating up. We treat those areas with a degreaser and a poultice before grinding, then check again. Occasionally an oil stain is bad enough that we cut it out and patch. We would rather tell you that at the start than watch a fish eye open in the base coat.
Cracks, and the difference between two kinds
Every slab cracks. Concrete shrinks as it cures and it has to relieve that somewhere. A hairline crack that has been the same width since 2009 is a cosmetic problem, and cosmetic problems get filled with a flexible repair resin during prep and disappear under the coating.
The other kind is a crack that moves. You can usually tell by looking at the edges: if one side sits higher than the other, or the crack is wider at one end and tapers, or it reopens every year at the same time, something under the slab is shifting. That is a subgrade issue. A coating will telegraph it back through, sometimes within a season, and no honest installer will tell you otherwise.
Spalling is its own category. That is the flaky, crumbling surface you get where road salt or freeze thaw has gotten into the top layer, common right inside the garage door where snow melt drips off a truck. Light spalling grinds out. Heavy spalling means the top of the slab has lost integrity and we are looking at resurfacing before any coating goes down.
The test grind tells us the truth
All of the above is inspection. The test grind is measurement. We run a diamond head over a small patch, usually somewhere out of the way, and read what comes up.
What we are reading
How hard the slab is, first. A soft, chalky slab cuts fast and throws pale dust. A hard, well finished slab fights the tooling. That determines which diamond grit we use across the whole floor, and getting it wrong means either polishing the concrete closed when we meant to open it, or gouging it.
Then, how deep the good concrete starts. If the top eighth of an inch is compromised, the grind shows us in the first pass. And finally what the aggregate looks like, which matters enormously if you are considering polished concrete instead of a coating, because on a polish the stone in the slab becomes the finished surface. Nobody knows what is in a slab until it is opened.
A test grind takes fifteen minutes and answers questions that guessing cannot. It is also the point where we occasionally tell somebody their floor wants a different system than the one they called about. That conversation happens more than you would think.
Signs your slab is in good shape
It is worth naming the happy case, because plenty of garage floors are ready as they sit. Water soaks in within a minute. No plastic sheet condensation. Cracks are hairline and static. No previous coating, or one that is completely intact with no lifted edges. No oil deeper than a surface stain. Reasonably flat, with the slope running toward the door rather than toward the back wall.
A slab like that is a straightforward flake epoxy job. Grind, repair the small stuff, base coat, broadcast, top coat. Two days on site, a day of cure, and you are parking on it.
Questions we get about garage slabs
My garage floor already has a coating on it. Do I have to remove it?
Usually yes, and mechanically. Even a coating that looks fine has an unknown bond to the slab, and putting a new system on top means your floor is only as good as somebody else’s prep from years ago. We grind it off and start from open concrete.
Does a new slab need to wait before it gets coated?
Yes. Fresh concrete is still giving up water for a long time after the finishers leave. The usual guidance is a month at minimum, and we still test rather than count days, because a slab poured in a wet February behaves differently from one poured in August.
Can you coat a floor with a drain in it?
We can, and the detail work around the drain is where it either lasts or does not. The coating has to turn down into the drain and terminate, not stop short and leave an edge for water to get under.
What if you find something bad once you start grinding?
We stop and tell you. Finding a problem mid grind is not common because the inspection and the test grind usually catch it, but it happens, and the answer is always a phone call rather than a coating over the top of it.
Photographs of real slabs before and after are in the gallery, and every one of them is our own work.
Not sure what shape your slab is in?
Send us a few photographs and we will tell you what we see. If it needs a test grind, we will come run one.
Serving Huntsville and North Alabama. Questions about a specific room go to our contact page.