Why prep is most of the job on a Louisiana slab
Baton Rouge garages sit on slab-on-grade concrete over a high water table, in air that stays humid most of the year. Older slabs were often poured without a vapor retarder, and flood-affected homes across the metro have concrete that was saturated and dried at least once. None of that stops a floor from being coated. It just means the coating is only as good as what was done to the slab first.
Step 1: Test the slab for moisture before anything else
Moisture comes first because it is the only step that can invalidate all the others — a perfectly ground, perfectly repaired floor under the wrong primer still lifts. The homeowner screen, a plastic square taped tight to the floor for a day or two, shows whether a slab is obviously sweating. It cannot show how much vapor is moving or which primer to use. That takes in-slab relative humidity probes or calcium chloride domes read over several days, and the result decides between a standard primer and a moisture-tolerant one. The method and the readings are in our post on concrete moisture testing before epoxy. It matters most on rebuilt and flood-repaired slabs, which is why moisture assessment leads every job in Denham Springs.
Step 2: Grinding vs. acid etching — and why grinding wins here
Acid etching comes in the kit because it fits in the kit. On a Baton Rouge slab it creates three problems: it does nothing to curing compounds, old sealers, or tire dressing; it deposits salts that have to be rinsed with water you are pouring into a slab you just tested; and the profile it leaves is at the shallow end of what any coating wants. Diamond grinding under a dust shroud solves all three. It strips whatever is on the surface, it is dry, and it leaves a uniform, open-pored profile. Grinders can be rented, but running one flat across a garage without dishing the slab is a learned skill.
Step 3: Cracks, joints, and spalls
Grinding is also the diagnostic step: hairline cracks and hollow spots invisible under old paint show plainly once the surface is opened. Cracks are routed clean and filled with a rigid repair compound, spalled edges are rebuilt with a mortar matched to the system, and everything is ground flush so the repair disappears under the coating. Caulk and hand-smoothed patch shrink and move, and the coating cracks along the line. Control joints are honored or filled deliberately, never just coated over.
Step 4: Oil, contaminants, and what the grinder cannot fix
Degreasing happens before grinding, because a grinder run over an oil spot smears it wider and drives it in. Deep stains get a poultice that draws the oil back out; the check afterward is a splash of water. If it soaks in, the slab is ready. If it beads, something is still sealing the surface. This is the one step a homeowner can do to a professional standard, and the drip spots are exactly where a coating lets go first when it is skipped.
Step 5: Profile and cleanliness check
After repairs, the floor is vacuumed with an industrial unit, not swept, because grinding dust settles into the very pores the coating needs to fill. The profile should look and feel uniform across the slab, and a strip of tape pressed to the concrete and pulled should come up clean. Dust on the tape means another pass.
Step 6: Humidity and dew point on coating day
Prep ends the morning of the install. The concrete surface has to be warmer than the dew point — the standard rule is at least five degrees — or moisture condenses under the wet coat and the film blushes or bonds poorly. In a Baton Rouge summer, with dew points routinely in the seventies, that can rule out early mornings on a slab that cooled overnight, and a closed bay door with moving air becomes the difference between a clean cure and a cloudy one. The wider story is on our page about how Louisiana humidity affects concrete floors.
DIY prep vs. pro prep, step by step
| Step | Typical DIY approach | Professional approach |
|---|---|---|
| Moisture test | Plastic sheet taped to the floor. A screen, not a measurement. | In-slab RH probes or calcium chloride domes, read over days. The result picks the primer. |
| Surface profile | Acid etch from the kit: weak profile, leftover salts, a freshly soaked slab. | Diamond grinding under a dust shroud. Strips sealers and curing compounds acid never touches. |
| Cracks and spalls | Caulk or hand-smoothed patch. Shrinks, moves, and the coating cracks with it. | Cracks routed and filled rigid, spalls rebuilt, everything ground flush. |
| Oil and contaminants | Degreaser, brush, hose. The one step a homeowner can do to a pro standard. | Degrease before grinding, poultice deep stains, water-drop test to confirm absorption. |
| Cleanliness check | Sweep. Dust and etch residue stay in the pores. | Industrial vacuum, then a tape pull. Clean tape is the pass condition. |
| Dew point on coating day | Whatever the weather is doing Saturday. | Surface temperature checked against dew point, install window chosen around it. |
The materials side of the same comparison is covered in DIY kit vs. professional garage floor coating.
What you can honestly do yourself
Plenty, and it helps. The steps that take labor rather than equipment are fair game before the walkthrough:
- Empty the garage completely, shelving included — coatings run wall to wall.
- Degrease the slab, especially the drip spots under the engine bay and around the mower.
- Tape plastic squares down in three spots for a day or two to flag a slab that is obviously sweating.
- Chalk-mark every crack and hollow-sounding spot before grinding dust hides them.
- Check the forecast for coating day and say so if the bay door has to stay open.
What prep costs
On a written garage quote, prep sits as its own line next to repair, the coating system, and the finish, so you can see what the grinding and testing actually cost against any other bid. The prep line does not swing much from garage to garage; repair is what moves. Significant crack or spall repair typically adds $200 to $800 on a residential garage, and the whole installed system lands at $6–$9 per square foot installed for most flake systems. Installed ranges and the full process are on the garage floor coating in Baton Rouge page. If the slab is a driveway or patio that needs protecting rather than a system, the prep is lighter and the answer is usually concrete sealing or resurfacing instead.
Frequently asked questions
How do you prep a garage floor for epoxy?
In order: test the slab for moisture, degrease, grind to a uniform profile, rout and fill cracks and rebuild spalls, grind the repairs flush, vacuum and tape-test, then confirm the surface is above the dew point before the first coat. On a Louisiana slab the moisture step is the one that can quietly undo all the others.
Is grinding or acid etching better before epoxy?
Grinding, and in Baton Rouge it is not close. Etching leaves a shallow profile, deposits salts that need rinsing with water the slab then has to release, and does nothing to curing compounds or old sealers. Diamond grinding strips all of that dry and leaves an even, open-pored profile the coating can key into.
Can I prep the garage floor myself and have a pro coat it?
You can do the parts that take labor rather than equipment: clear the space, degrease, mark cracks, run a plastic-sheet screen. Grinding, quantitative moisture testing, and crack routing need tools most homeowners do not own, and an installer redoes those steps anyway. Skip the etching.
Do I need a moisture test before epoxy in Louisiana?
Yes. Slabs here sit on wet ground, many older ones were poured without a vapor retarder, and flood-affected concrete around the metro carries residual moisture behavior for years. A slab that fails can still be coated with a moisture-tolerant primer, but only if the test happened.
How much does concrete prep cost before epoxy?
On a written garage quote, prep is its own line alongside repair, the coating system, and the finish. The prep line itself is fairly steady from garage to garage; repair is the number that moves. Significant crack or spall repair typically adds $200 to $800 on a residential garage, depending on how much routing and rebuilding the slab needs.
Prep gets scoped at the walkthrough
Every step above gets assessed on your actual slab: the moisture readings, the cracks the grinder will find, the repairs the price depends on. Call (225) 457-3961 and we will set up a time to walk it.
Serving Baton Rouge and the surrounding metro, including Prairieville, Gonzales, Denham Springs, Zachary, Central, Baker, Walker, Port Allen, Addis & Brusly, and St. Gabriel.