Concrete waste factors that actually match the field

Most estimators use the same 5% waste factor on every pour. The field tells a different story. Here are the numbers we see across slab, wall, footing, and pier work.

Open any estimating template and you'll see the same number in the waste column: 5%. It's the default in most software, the default in most spreadsheets, and the default in most heads. It's also wrong on more pours than it's right.

Waste isn't a single number. It's a function of geometry, pump type, weather, crew, and how clean the subgrade is the morning of the pour. Treating it as a constant is how you end up short a truck on Friday at 2pm.

These ranges come from field-verified delivery tickets against takeoff CY on 60+ commercial pours we've helped reconcile in the last 18 months.

Large open slabs (warehouse, distribution): 2–4%. Geometry is forgiving, the screed line is straight, and most of the waste is at the edge form and the pump cleanout. Slabs with depressions, thickened edges, and equipment pads: 5–8%. Every transition in thickness adds a place for over-pour. Slabs poured against existing: 7–10%. Match lines are never as clean as the plan shows.

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