The number nobody argues with
The estimate said 90 tons. The tickets from the plant add up to 104. Nobody stole anything, and the crew paved the lot they were told to pave. You still bought 14 tons of hot mix you didn't bill for. At $85 a ton that's $1,190 in mix alone, before the trucking and the crew time to put it down.
That gap is yield: the tons you actually placed compared with the tons you figured from area and depth. It's often the biggest cost variance on a paving job, and it's easy to ignore, because the tickets come in over a few days, the job looks fine, and the invoice matches the proposal.
The formula is right. The lot isn't.
The tonnage math is honest: area × depth ÷ 12 × unit weight ÷ 2,000. For 20,000 square feet at 3 inches and 145 pounds per cubic foot, that's 362.5 tons. But the formula assumes a flat surface at exactly 3 inches everywhere, and no lot is like that.
Here's where the extra tons go.
Depth creep. The spec says 3 inches. The screed gets set a hair heavy, because thin spots fail and thick ones don't. A quarter inch over across the whole lot is 8 percent more mix. Nobody notices a quarter inch. You'll notice 8 percent.
The surface underneath. On an overlay, ruts and low spots fill with mix before the lift even starts. On new work, a base that isn't tight to grade does the same thing. The paver lays a level mat over whatever's under it, and the difference comes out of your pocket.
Edges and hand work. Around structures, along the curb and against buildings, mix gets placed by hand and raked. Hand work runs heavy. It also makes waste: the cleanup, the pile at the end of the pull, the load that showed up late and went cold.
Truck and hopper waste. Every load leaves a little in the bed, and every day ends with some in the hopper. It's small per load and real over a season.
Unit weight. 145 pounds per cubic foot is a default, not your mix. If your plant's mix weighs 148 compacted, you need about 2 percent more tons than the default says. At 150, it's about 3½ percent. Ask the plant for the number on the mix design.
Stack those up on a rough lot and double-digit overruns aren't unusual. The point is that they're predictable, and your estimate should expect them.
A waste factor isn't the same as knowing your yield
Most estimators handle this with a waste factor, often 5 to 10 percent on top of the calculated tons. That's a fine place to start, and it's where most people stop. But a flat factor treats every job the same, and jobs aren't the same. An overlay on a rutted lot needs more than a mill and fill on a fresh milled surface. New work on a well-graded base needs less than either.
The better number is yield by job type, and the only way to get it is to measure it. Divide ticketed tons by calculated tons on every job, and group them by type. After a season you'll have a number for overlays, one for mill and fill and one for new pavement, and they won't match.
Where the money goes
Take that 14-ton overrun at $85 a ton: $1,190 in mix. The tons had to be transported, so add trucking. They had to be placed, so add some crew time. And if the overrun means one more late load that gets rejected, add that load too.
Now run it across a season. Thirty jobs at $1,200 each is $36,000 of mix you bought, transported and placed without billing anybody for it.
The frustrating part is that nobody on site made a mistake. The money went to an estimate that left out a number it should have had.
What to do about it
Get the real unit weight. Your plant's mix design lists it. It's the cheapest fix on this list.
Measure the lot, not the drawing. If the takeoff came off the plan sheet, walk it. If you're paving over an old surface, look hard at the ruts and low spots and bump the factor to match.
Check depth during the pull. Probing the mat behind the screed a few times per pull catches depth creep before it costs a whole lot's worth of tons.
Add up the tickets the same day. Not at month end. The day after paving, total the tickets, compare them with the estimate and write down the yield. If it's 12 percent over and you allowed 7, you've learned something while you still remember why.
Put the overrun into the next estimate. A factor that comes from your own jobs is the whole point. It makes the next estimate a little higher and a lot more honest.
Bill for what changed. If the overrun came from something the customer asked for or the site hid, that's a change order, not yield. A base that had to be undercut, an area added on site, a depth the owner's rep asked you to increase: those need a signature before the extra mix goes down.
The number to watch on every job
One line: tons ticketed ÷ tons estimated. Your own history should set the thresholds, but here's a starting point. Under 1.05, the estimate was good, or you got lucky. Between 1.05 and 1.15 is the range a waste factor should cover on a rough lot. Over 1.15, something happened on that lot that's worth a phone call to the foreman.
Track it, and by next season you'll know your yield by job type better than the plant knows its own mix.
Where Pavr fits
Pavr is job management software for paving, sealcoating, striping and concrete contractors. In Pavr the tons are a line on the estimate with a quantity and a cost, so the allowance you add is written down instead of living in someone's head. When the job runs, the foreman logs material on the daily log, and once it's approved it posts against that line, with the difference from the estimate in dollars.
When the overrun came from an undercut or an added area, send a change order from the job. The customer signs it on their phone, that part of the job waits until they do, and once it's signed it goes on the invoice. See how job costing works.
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