The 28-Day Break Decides a Pour You Already Billed
You poured in March on an approved mix, the cylinders broke low in April, and two floors are already sitting on the slab in question.
Almost every other trade gets inspected while its work is still exposed and still cheap to fix. Concrete gets a verdict four weeks after the fact, on work that other trades have already built on top of, which means the remedy is demolition of somebody else's progress before it's demolition of yours. The mix approval clock on the front end works the same way, since it puts dead time on a mobilized crew while a lab and an engineer who feel no pressure from your payroll decide when you can batch.
The size of it
Coring, load testing, and remedial work are unbudgeted direct costs that hit the current period against a job phase you closed a month earlier. Until the dispute settles, the GC withholds against the entire pay application, not just the disputed pour.
There are two clocks on every placement and you own neither one. Before the first truck, the mix design goes to the engineer of record and the testing lab with historical strength data for review, and until it comes back approved you can't batch a yard. After the pour, acceptance runs backward: cylinders break at 28 days, and a low break triggers core drilling, load testing, engineering evaluation, or removal. By then the slab is buried under subsequent work and the pay application it was billed on has already been approved.
Three moves, in order
Step 06: Project management
Billing dates, change orders, and notices, run as standards that hold without anyone chasing them.
What else costs concrete contractors money
The same mechanism in other trades
What concrete owners ask
Failed cylinder break at 28 days who pays for coring?
You poured in March on an approved mix, the cylinders broke low in April, and two floors are already sitting on the slab in question.
What does it cost?
Coring, load testing, and remedial work are unbudgeted direct costs that hit the current period against a job phase you closed a month earlier. Until the dispute settles, the GC withholds against the entire pay application, not just the disputed pour.
What do I do first?
Keep the pour phase open in job cost until the 28-day break comes back, so late charges post to the placement that caused them.
What are concrete contractors supposed to be making?
Concrete runs 21% gross margin, 14% overhead and 7% net profit before taxes at $1M–$5M. The all-trade average is 7%, so this trade sits right on it. The CFOS target is 10%.
Which part of the system fixes it?
The step is number 06, project management. Billing dates, change orders, and notices, run as standards that hold without anyone chasing them. It comes from chapter 6 of CONTROL: The Construction Financial Operating System.
Josh Luebker ran commercial construction projects before he ran the numbers behind them, on data centres, military bases, hospitals, and high-rises. He wrote CONTROL: The Construction Financial Operating System, which is an eight-step framework for commercial subcontractors, and it publishes on October 1, 2026. He is a master electrician who moved into the office and kept the field vocabulary.
Sulphur Prairie Operations LLC maintains the benchmark reference behind these figures. Every edition is reconciled against the newest CFMA survey release before it publishes here. Where a figure changes between editions, the older edition keeps its year in the title so a citation to it stays correct.