In Plain English
Quick Answer
A concrete floor poured directly on the ground, used in warehouses, garages, and homes.
Definition
Definition
A concrete floor slab that is cast directly on prepared, compacted subgrade or base material at or near ground level. Slab-on-grade construction is common for warehouses, retail buildings, and residential construction where frost depth, soil conditions, and loads permit. The slab is typically reinforced with welded wire fabric or rebar and may include control joints to manage cracking.
Context
Why It Matters in Bidding
Slab-on-grade scope ties together earthwork, vapor barrier, reinforcement, and concrete line items, so an estimator must coordinate several trades to price it accurately and avoid double-counting or gaps. The thickness, reinforcement, and base preparation called out in the structural drawings drive cost significantly, and assumptions about soil conditions or required compaction can expose the bid to risk if geotechnical requirements are missed.
Example
Example
Taking off a 40,000-square-foot warehouse floor, the estimator prices the slab by cubic yards of concrete plus square footage of welded wire reinforcement, vapor barrier, and fine grading, then flags a thickened edge detail at the dock walls as a separate quantity.
See Also
Related Terms
FAQ
Questions Contractors Ask
How do you estimate a slab-on-grade in a takeoff?
Concrete is quantified by cubic yard from area times thickness, with thickened edges and integral footings counted separately. Reinforcement, vapor barrier, base stone, fine grading, control-joint sawing, and finishing each carry their own units. Coordinating these trades prevents overlap with the earthwork scope and avoids missed components.
What slab details add cost beyond the basic flatwork?
Thickened edges, integral footings, embeds, dowels at joints, special finishes like power-troweling or sealer-hardener, and increased thickness for heavy loads all add cost. Subgrade improvement for poor soils can be substantial. Reading the structural notes and geotechnical report keeps these extras from becoming unbid surprises during construction.
Why do control joints matter when pricing a slab-on-grade?
Control joints manage shrinkage cracking and are usually saw-cut or tooled on a grid specified by the engineer. They add labor and equipment time proportional to linear footage. Tighter joint spacing or specialty joint fillers increase cost, so the estimator should price joints separately rather than assuming they are included in finishing.
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