Garage Floor Coating Coverage, Mils, Prep, Moisture, Cure Schedule, and Cost

Gallons and kits for your floor at the mils you want, the prep and moisture test that decides whether the coating stays on, the cure and drive-on schedule, the product pick, and the failure modes with the price per sq ft.

Coverage is a solids math problem: 1 gallon of coating that is 100 percent solids covers 1,613 sq ft at 1 mil, so coverage at your target is 1,613 divided by the mils you want. Epoxies run 55 to 80 percent solids, polyaspartic and polyurethane topcoats run 80 to 100 percent, and a solvent epoxy at 45 percent solids uses three times the gallons to reach the same dry film. The two numbers that decide whether the floor survives are the moisture vapour transmission rate through the slab and the surface temperature relative to the dew point, and both are measured, not estimated.

—Gallons and kits at your mil thickness
—Broadcast flake, topcoat, and anti-slip
—Grind, etch, patch, and the moisture test
—Install window, cure, and drive-on date
—Material, contractor, and cost per sq ft
—The failure modes and what causes them
How the math works
  • Coverage: 1 gallon of 100 percent solids covers 1,613 sq ft at 1 mil. Gallons per coat = sq ft times wet mils per coat divided by (1,613 times the solids fraction), with 12 percent working waste, and wet mils per coat = target dry film mils divided by the number of coats, scaled by the solids fraction.
  • Solids: a solvent epoxy runs 45 to 55 percent, a 100 percent solids epoxy 95 to 100 percent, a water-based epoxy 55 to 65 percent, a polyaspartic 85 to 95 percent, and a polyurethane topcoat 80 to 90 percent. The gallons follow the solids number, not the price per gallon.
  • Moisture: 4 lb per 1,000 sq ft per 24 hr maximum under ASTM F1869 calcium chloride, 75 percent maximum in-slab relative humidity under ASTM F2170, and the manufacturer number on the data sheet, tested before the primer, not after the peel.
  • Dew point: surface temperature at least 5 F above the dew point at the coating moment, ambient 50 to 90 F, humidity under 85 percent, slab above 50 F. A surface at the dew point condenses under the film.
  • Cure: foot traffic at 6 to 18 hours, vehicles at 48 to 96 hours on polyaspartic and 4 to 7 days on epoxy, full chemical cure at 7 days on epoxy, and hot tire pickup is the 72 hour to 7 day line, not the walk-on line.
Floor coating planning tool on standard coating solids coverage math, the ASTM F1869 and ASTM F2170 moisture limits used across the coating industry, the concrete surface profile scale (CSP) used by the flooring-repair manufacturers, and standard application practice from the manufacturer data sheets. Manufacturer system requirements, the moisture limit on the specific product, a required moisture mitigation epoxy, a required primer on a sealed slab, a required profile number, a required re-coat window, a required pot life, a required temperature and humidity range, a required anti-slip rating, a required static and a required coefficient of friction test, a required floor flatness and levelness number, a required floor in a commercial kitchen, a required floor in a food plant, a required floor in a clean room, a required floor in an EPA lead RRP containment, a required floor in a healthcare occupancy, a required floor in a fuel and a chemical exposure area, a required floor in a public way, a required slip test on a ramp, and a required floor assembly listing are all manufacturer and authority-having-jurisdiction questions. A slab with a high water table, a slab with no vapor barrier, a slab poured over a radiant tube, a slab with a hair-crack network, a slab with a power-troweled finish, a slab with a curing compound, a slab with a coating in place, a slab with a moisture problem, a slab in a basement, a slab that has been oil soaked, a slab in a food plant, and a slab in a warehouse with a forklift aisle are all specified by the coating manufacturer technical representative and not sized by a calculator. Coating, flake, aggregate, grinder rental, and installed contractor prices vary by region and by brand, and a warranty is only as good as the moisture test on the record.

How many gallons of epoxy do I need for a 400 sq ft garage?

About 6 to 9 gallons of a 100 percent solids epoxy at 20 to 24 mils of dry film across three coats, ordered as 2 to 3 three-gallon kits with a 12 percent working waste. Coverage runs from 1,613 sq ft per gallon at 1 mil of 100 percent solids, so a 68 percent solids product at 8 wet mils per coat needs more than twice the gallons to reach the same dry film.

Do I have to grind a garage floor before epoxy?

Yes on a power-troweled slab: diamond grind, shot blast, or scarify to a CSP 2 to CSP 3 profile with the bare aggregate visible. An acid-etch kit fails on a hard-troweled slab, a slab over ten years old, a slab with a sealer, and a slab with a curing compound, and a coating over a sealer lifts in sheets at the first hot tire. Grind, patch, vacuum, and tack-rag the floor before the primer opens.

How do I know if my slab is too wet for a coating?

Test it: a calcium chloride test at 4 lb per 1,000 sq ft per 24 hr maximum under ASTM F1869, an in-slab relative humidity sensor at 75 percent maximum under ASTM F2170, and a plastic sheet taped down for 18 days with a dark slab under the film as the field check. The test kit costs 120 to 220 dollars, and a coating on a slab over the limit is a full removal at 2 to 4 dollars per sq ft with a moisture mitigation epoxy on top of it.

When can I park on a new garage floor coating?

Foot traffic at 6 to 18 hours depending on the system, and vehicles at 48 to 96 hours on polyaspartic and 4 to 7 days on a 100 percent solids epoxy. Hot tire pickup is the failure to protect: a tire parked on a floor inside the cure window pulls the coating off in a tire-shaped disk, and it is the most common warranty claim in the industry. Drive on gently for the first week and never park on a warm floor inside 72 hours.

What does a garage floor coating cost per square foot?

DIY material and prep on a 400 sq ft garage at 2.50 to 3.50 per sq ft on a flake epoxy system with the grind, the flake, and the moisture test, about 1,100 dollars all-in. Contractor installed on the same spec runs 3.50 to 6 dollars per sq ft, polyaspartic runs 5 to 8 dollars installed, a two-coat epoxy 2.50 to 4.50, and a penetrating sealer 70 cents to 1.50 per sq ft.

Related tools

Concrete curing and maturityA new slab and the coat window Slab thickness by loadThe slab under the coating Concrete bags for a slabPatching and the bag line Radon mitigation sizingA coating over a radon membrane Mold remediation containmentA floor with a moisture history Expansion tank sizingA garage with a closed water system