Ten cubic yards is the number to plan around
Ready mix is sold and delivered by the load, and a standard load is 10 cubic yards. That is the figure to plan with and the figure a batch plant will use when you call and describe a pour. What a drum could physically hold is a different question from what a truck will carry on the road to your address, and the plant settles that for their own trucks and their own routes. Ask them when you order and you will get a plain answer.
The part that catches people out is that an order rounds up. Concrete does not arrive in the exact amount you calculated. If your pour works out to eleven yards you are ordering two loads and the second one comes mostly empty. If it works out to nine and a half you are ordering one.
- One standard load is 10 cubic yards
- Add 10 percent to your calculated volume before you do anything else
- Then round up to the next whole load
Your slab becomes yards before it becomes trucks
Before anybody counts trucks, the slab has to become a volume. Multiply length by width for square feet. Multiply that by the thickness in feet, so 4 inches is a third of a foot and 5 inches is a little over four tenths. Divide the cubic feet by 27 and you have cubic yards.
Then add the 10 percent. Nothing on a job site is as exact as the calculator makes it look. Boards bow a little under pressure, the graded subgrade has low spots you cannot see once the stone is on it, and there is always material left behind in the chute and the hopper. Order the calculated figure exactly and you finish the last few feet of a slab short, with everything behind you already stiffening. That allowance goes on before you round up to the load, not after.
Where the load boundary falls on a real slab
Take a 24 by 24 garage slab, which is 576 square feet, poured at 5 inches. That is 240 cubic feet, or 8.9 cubic yards calculated. With the waste allowance it comes to 9.8. One load, with very little room left in it.
Now widen that slab by a single foot. At 25 by 24 it is 600 square feet, 9.3 cubic yards calculated and 10.2 with waste. Two loads, for one extra foot of building. That is not a quirk of the arithmetic, it is the reason we run the yardage with you before the dimensions get set. Sometimes the sensible move is to trim back inside the load. Sometimes it is to use the room, because the second truck is coming either way and anything you add on top of that boundary is the cheapest concrete on the whole job.
When one pour takes more than one truck
Past a single load the trucks arrive in sequence, and the gap between them is what matters. Concrete placed against concrete that has already begun to set does not knit together, and you are left with a cold joint running through the slab. The way that gets avoided is scheduling, so the second truck is backing in while the first is finishing out rather than showing up forty minutes behind it.
That is also where our own line pump earns its keep on a bigger pour. A line moves concrete to the forms faster than a crew can take it by hand, so the pace of the day becomes how fast the finishers can screed rather than how fast the concrete can reach them.
What the load count does to what you pay
That same 576 square foot garage slab, priced at the garage slab band of $8 to $12 per square foot installed, plans out at $4,608 to $6,912. The concrete, the delivery and the waste allowance all sit inside that number rather than arriving beside it on a separate ticket. So does the placement, because we own our pump and run it with our own operator and hose guy on our own pours.
Our cost pages carry the full bands and the reasons two bids for one job come back different. What belongs here is narrower. Ready mix comes in whole loads, and a pour sitting just over a boundary has paid for concrete that was ordered rather than concrete that was placed. We will show you exactly where your slab lands when we measure it, before anything gets ordered.