How to epoxy a garage floor
A fresh epoxy coating turns a stained, dusty slab into a bright, wipe-clean floor that shrugs off oil and tire marks — and it's a realistic weekend project, as long as you respect the prep. A typical 2-car garage (about 400 sq ft) takes roughly two 2-car kits (or four 1-car kits) for a durable two-coat finish. Here's how to do it, and how much epoxy to buy.
Will epoxy actually stick to your floor?
Epoxy is only as good as the concrete under it and the prep you do. Before anything else, run these checks — they decide whether the coating lasts ten years or peels in one:
- Is the slab fully cured? New concrete needs to cure about 28 days before you coat it.
- Is it dry underneath? Tape a 2×2 ft square of plastic sheeting tight to the floor overnight. Condensation under it — or darkened concrete — means moisture is wicking up through the slab, and epoxy will blister. Solve the moisture problem first.
- Is it bare? Epoxy won't bond to a concrete sealer or old paint. Sprinkle water on the slab: if it beads instead of soaking in, the concrete is sealed and must be ground to bare.
- Is it sound? Flaking, spalling, or heavily pitted concrete needs patching first (and severe cases may not be a good candidate at all).
How much epoxy do you need?
Garage epoxy is sold in kits — a 1-car kit covers about 250 sq ft per coat and a 2-car kit about 500 sq ft per coat (you can also buy it by the gallon). Bare, porous concrete drinks up the first coat, so it covers a little less. Because a lasting finish is a colored base coat plus a clear topcoat, plan on two coats:
Kits = floor area × coats ÷ coverage per kit
For a 20 × 20 ft two-car garage at two coats:
- Area: 20 × 20 = 400 sq ft
- Coverage needed: 400 × 2 coats = 800 sq ft
- Kits: 800 ÷ 250 = 3.2 → 4 one-car kits, or 800 ÷ 500 = 1.6 → 2 two-car kits
Get your exact kit count and cost
Enter your garage size and coats and our calculator gives the epoxy kits you need, plus the estimated cost.
Open the Garage Floor Epoxy CalculatorWhat you'll need
- Epoxy kit(s) — water-based is the easiest DIY option; 100% solids is the most durable but less forgiving
- Concrete degreaser and a stiff deck brush
- Concrete etcher (acid or citric) or a rented diamond grinder to profile the slab
- Concrete crack filler / patch compound
- A ⅜″ nap roller and extension pole, plus a brush for cutting in edges
- Decorative color flakes and/or an anti-slip additive (optional)
- Spiked shoes if you're broadcasting flakes or rolling a large floor
- Plastic sheeting and tape for the moisture test, plus gloves and eye protection
Step by step
- Clear and clean. Empty the garage, sweep, then scrub oil spots and the whole floor with degreaser and rinse. Any grease left behind will stop the epoxy from bonding.
- Repair cracks and pits. Fill cracks and holes with a concrete patch, smooth them flush, and let them cure per the label.
- Profile the concrete. This is the make-or-break step. Acid- or citric-etch the slab (follow the dilution, work in sections, and scrub) or diamond-grind it. Either way you want a texture like medium sandpaper so the epoxy can grip.
- Rinse and dry completely. Rinse etched floors thoroughly — twice — so no residue remains, then let the slab dry fully, usually 24 hours. Re-run the plastic-sheet moisture test if you're unsure.
- Tape and plan your exit. Tape off the base of the walls, and plan to coat away from your exit so you don't paint yourself into a corner.
- Mix the epoxy. Combine parts A and B and stir thoroughly; let it sit (induct) if the instructions say to. Only mix what you can roll out within the pot life — often just 20–40 minutes for solids — because it hardens in the bucket.
- Cut in the edges. Brush a band around the perimeter and around posts so you can roll the open floor without stopping.
- Roll the base coat. Work in 4×4 ft sections, rolling thin and even. If you're using flakes, broadcast them onto the wet coat as you go.
- Apply the clear topcoat. Within the recoat window (usually the next day), scrape and vacuum any loose flakes, then roll a clear topcoat for durability and sheen.
- Cure before use. Keep off it for about 24 hours, then wait 72 hours (up to a week for 100% solids) before parking a car on it.
Mistakes to avoid
| Mistake | Why it matters |
|---|---|
| Skipping the etch or grind | Without a profile the epoxy has nothing to grip — it peels in sheets |
| Coating damp or new concrete | Trapped moisture blisters the coating; let new slabs cure ~28 days |
| Mixing the whole kit at once | Epoxy sets in the bucket — mix only what you can spread in the pot life |
| Working in heat or direct sun | A hot slab outgasses and leaves bubbles and pinholes; aim for 60–85°F |
| One thin color coat only | Wears through fast — a clear topcoat is what makes it last |
| Coating over a sealer | Epoxy can't bond to sealed concrete; grind it to bare first |