How to Prep a Garage Floor for Epoxy in New Orleans

Prep is most of the work on a coated floor, and almost every requirement below comes straight from coating makers' data sheets — the documents installers are supposed to follow. Whether you are doing a kit yourself or checking a professional's plan, this is the sequence.

The seven steps

Step 1: Empty the garage and look closely

Everything comes off the floor, including anything bolted down that can be lifted. Look for cracks, spalled edges, oil spots, white powdery deposits, and any spot that stays dark after the rest of the floor dries — and note where water comes in under the door or along a wall.

Step 2: Check for sealer and old paint

Drip a little water on the floor in several places. If it beads instead of soaking in, there is a sealer on the slab, and it has to come off before coating. If there is paint or an old coating, anything loose is sanded and scraped off, and what remains is tested for adhesion; a coated floor that stays is at least scuff sanded so the new coat can grip.

Step 3: Test for moisture

In much of the metro, groundwater can sit close to the ground surface. Moisture in a slab can make a floor coating fail after it goes down, which is why coating makers generally require a moisture test first. There are three standard methods: an in-slab relative humidity test (ASTM F2170), a calcium chloride test that measures vapor coming off the surface (ASTM F1869), and a plastic-sheet check that indicates whether moisture is present (ASTM D4263). The plastic sheet is a reasonable first look for a homeowner; the measured tests are what a professional quote should cite. Details are in the moisture testing guide.

Step 4: Degrease and clean

One coating maker's data sheet lists what a slab must be free of before priming: dust, dirt, existing paint films, efflorescence (the white mineral deposit), weak surface laitance, hydraulic and fuel oils, brake fluid, grease, fungi, and mildew. In a garage, oil drips under the cars and mildew in damp corners are the usual suspects. Heavy stains are degreased before the floor is profiled.

Step 5: Give the concrete a profile

A coating holds by gripping the texture of the concrete. The industry describes that texture on a concrete surface profile (CSP) scale from 1, nearly flat, to 10, very rough, set out in an ICRI guideline for preparing concrete for coatings. One professional epoxy floor system calls for mechanical preparation to CSP 3–4, and coating makers' sheets refer to mechanical methods such as shot blasting for this step. A big-box kit uses a mild citric-acid etch instead, which suits its thin single coat but is not what a full-build system specifies.

Step 6: Repair cracks, holes, and low spots

Cracks, pits, and low spots are filled with a repair product compatible with the coating — one maker's data sheet calls for repairs, filled blowholes, and leveling to be done with its own profiling mortar. The same sheet sets a minimum concrete strength at the time of application, which is a reminder that a coating cannot fix crumbling concrete. Significant repair on a garage usually adds $200 to $800 to the job.

Step 7: Vacuum, then check the conditions

Grinding dust is vacuumed off completely — dust is on the list of contaminants for a reason. Then the weather: South Louisiana has a hot, humid climate, and humidity can matter twice for a coating: moisture in the slab, and condensation on a cool slab during application. Coating makers want the slab at least 5°F above the dew point, and their data sheets tell installers to measure slab moisture, air humidity, temperatures, and dew point right before applying. One kit limits application to air temperatures of 60 to 85°F, and new concrete should cure at least 28 days before any coating goes on.

Doing it yourself vs. hiring it out

Steps 1 through 4 are within reach of most homeowners. Step 5 is where a kit and a professional system part ways: mechanical profiling takes professional equipment, and it is the step full-build systems specify. The DIY kit vs. professional comparison covers when a kit is a sensible choice. If a professional is doing the work, ask which steps they want done before they arrive — often just an empty floor and a note of where water comes in — and which they include in their own prep line. The cost guide shows what professional prep adds.

Old paint in an older house: a lead warning

Many garages in older houses carry layers of old floor paint. Before anyone scrapes or sands it, read the warning printed on one kit maker's own data sheet: scraping, sanding, or removing old paint may release lead dust, and lead is toxic — especially to children and during pregnancy. The same sheet calls for a NIOSH-approved respirator and cleanup with a HEPA vacuum and a wet mop. If the house is old enough that the paint might contain lead, have it tested before the grinder comes out.

The same data sheet sets a simple rule for old paint that is staying: test its adhesion, and if more than a quarter of it comes off, remove all of it before coating.

How prep shows up on a quote

Prep is the first of the four lines a written quote should break out: the preparation method, the moisture test, and any moisture-tolerant primer the reading calls for. Repair — cracks, spalls, and removal of old coatings — is the second. When those two lines are vague, ask for them in writing before comparing totals.