Concrete construction, such as for garage slab floors, has many steps and components. According to ConcreteNetwork.com, the breakdown of costs at the time of publication was as follows: Grading flattens the ground for the concrete and costs $50 per hour. The sub-base -- the sand or gravel on which the concrete rests -- costs about $12 per cubic yard. Setting up concrete forms and finishing the concrete costs $1 to $1.50 per square foot. Finally, reinforcement prevents cracking through the addition of wire mesh, rebar, plastic mess or fiber to the mix. This costs about 10 cents per square foot. As for the cost of concrete, the national average price in 2008 was $75 per cubic yard.
The cost of a plain concrete garage floor runs between $2.50 to $4.50 per square foot depending on size and complexity, according to ConcreteNetwork.com. This does not include any decorative finishes such as stamping, staining or epoxy. A minimum one-car garage measures 12 feet wide by 22 feet long for a total of 264 square feet. A slab for this would run $660 to $1,188 total. A minimum two-car garage runs 18 feet wide by 22-feet long for a total of 396 feet. The slab for this runs $990 to $4,455. Note that these are minimums. Many homeowners choose far larger spaces for their garages.
Coatings add decorative finishes to concrete garage floors and increase its usability. Simple concrete paint, with about two coats, lasts about a year and costs from 75 cents to $2.25 per square foot. Residential grade epoxy paint lasts two to five years and runs $1 to $2.25 per square foot. Solid epoxy requires the services of professional installers but can last many years. It costs $1.50 to $3 per square foot. Color flake lasts up to 15 years and costs from $3.50 to $5.50 per square foot. All prices are from the Concrete Ideas website at the time of publication.
Homeowners can save money on a concrete garage floor by pouring their own. But the job is so complex that most people call in professionals to perform it. Labor costs for concrete masons vary across the country, with an average of $18.89 per hour, according U.S. Bureau of Labor Statistics as of May 2010. The highest labor costs are in Alaska at $31.37 per hour, Hawaii at $29.21 per hour and New York at $27.52 per hour. Wages are below average in South Dakota at $14.20 per hour, Nebraska at $15.27 and North Dakota at $16.37 per hour. Note that these are not the hourly costs for building a concrete garage floor, but a relative comparison of labor costs across the country.