Don Vandervort, Head Homeboy, has written more than 30 DIY home improvement books, been a segment host on HGTV, served as MSN.com's home improvement expert and written countless magazine articles.
Begin by taking careful measurements of the area to be filled with concrete. A discrepancy of only 1/2 inch can make a big difference in the amount of concrete you will need.
When ordering, tell the supplier the square footage and depth. A reliable supplier will calculate how much you will need, but you want to double-check these calculations against your own.
Concrete is usually sold by the cubic yard, just called a yard. A yard of concrete (or sand or gravel) fills an area 3 feet by 3 feet by 3 feet. For a small project, such as a pier footing, you may choose to measure cubic footage instead; bags of dry-mix concrete often include cubic footage measurements on the package.
It is very easy to figure out concrete needs. For a footing or for a rectangular slab, simply multiply the width in feet times the length in feet times the thickness in inches.
Divide the result by 12 to get the number of cubic feet. Divide that number by 27 to get the cubic yards. For example, if a slab measures 20 feet by 30 feet and its thickness is 3 1/2 inches:
20 x 30 x 3.5 = 2,100 2,100 / 12 = 175 cubic feet 175 / 27 = 6.48 yards
Adding about 10 percent for waste, you would order a little more than 7 yards. If you need more than 1/4 yard of concrete, ordering ready-mixed concrete is usually worth the extra expense.
A 60-pound sack of dry-mix concrete makes around 1/2 cubic foot, meaning that you would need to mix 52 bags to make 1 yard of concrete. Many ready mix concrete companies will not deliver less than a yard of concrete. Others have special trucks designed to mix smaller amounts at the job site. If one company won't deliver a small amount for you, just keep calling around.
Patio Roofs & Gazebos All you need to know about building outdoor structures, from an inspirational gallery for unique ways to extend your living space outdoors, to step-by-step photo sequences to build an outdoor structure precisely suited to your needs.
