Why a 10% Waste Factor is Non-Negotiable in Concrete Ordering

There is nothing more stressful in construction than being "short" on a concrete pour. As the truck runs empty and you still have 4 feet of formwork to fill, the panic sets in. This is entirely avoidable by following the 10% rule and using an accurate concrete estimator.

The Reality of the Job Site

You might think your forms are perfect and your math is flawless, but concrete is lost or "displaced" in several ways that are hard to see with the naked eye:

• Subgrade Variations: Soil and gravel are rarely laser-level. A slight dip of 1/2 inch across a 20x20 patio adds nearly 0.75 yards.
• Form Deflection: Concrete is incredibly heavy (4,000 lbs per yard). This weight pushes against your wood forms, causing them to bow out slightly. This "stretch" eats up volume.
• Spillage and Residue: Concrete sticks to the inside of the truck mixer, the chutes, and your wheelbarrows. Some is always lost during the transfer from truck to form.
• Pump Lines: If you are using a concrete pump, several wheelbarrows worth of concrete will remain in the lines at the end of the job.

The High Cost of Being Short

If you order 5 yards and need 5.25, you have to call for a "balance." Most ready-mix companies charge a "short load fee" for anything under 4 yards, which can range from $150 to $300 on top of the concrete price. Furthermore, you now have a "cold joint" where the first batch of concrete starts to set before the second batch arrives, creating a permanent weak point and an ugly line in your finished work.

The "Better to Have it and Not Need it" Rule

Always round up to the nearest quarter or half yard, and then add 10% using our yardage calculator. If you end up with a small amount left over, have a small secondary project ready—like a few stepping stones or a small trash can pad—so the extra concrete doesn't go to waste.