Concrete is one of the more forgiving trades to eyeball — and one of the easiest to quietly lose money on, because the mistakes don't look like mistakes. They look like normal estimating.
Mistake 1: A waste factor that doesn't account for the pour type
Flatwork on a simple, open slab wastes differently than a job full of thickened edges, steps, and formed details. A flat waste percentage applied across every pour type either overprices your simplest jobs — costing you bids — or underprices your complex ones, where waste, over-pour, and rework add up fast. The fix is treating waste factor as a variable tied to pour complexity, not a fixed number you carry job to job.
Mistake 2: Reinforcement and accessories treated as an afterthought
Rebar, mesh, vapor barrier, control joint material — these get priced almost as a rounding error compared to the concrete itself, but they add up, especially on jobs with tighter reinforcement schedules or added accessories the plans call out. When these are estimated loosely instead of calculated against the actual reinforcement plan, the gap between "close enough" and "actually accurate" becomes real money by the time the job wraps.
The root cause
Both of these mistakes share a root cause: treating concrete as simple because it's familiar, rather than treating each pour as its own specific set of quantities. Familiarity is what makes estimators fast. It's not what makes them accurate — those are two different skills, and the second one requires actually re-measuring instead of remembering.
If concrete takeoffs are where your bids tend to run loose, it's worth revisiting whether your waste factor and reinforcement pricing are calculated per job or carried over from the last one.