Concrete slab cost is often underestimated because homeowners focus on square footage and miss the variables that make a small slab significantly more expensive than the raw material cost would suggest.
Thickness specification
A 4-inch slab uses roughly 25% more concrete than a 3.5-inch pour at the same area. Under-specifying slab thickness to save money is the source of many early slab failures.
Base preparation
The most variable cost item in slab work is what happens to the ground before the concrete is placed. A clean, compacted base requires minimal prep. A soft, contaminated, or poorly graded base requires excavation, import material, and compaction.
Access for equipment and material
For small slabs in tight locations, getting material to the pour area is the dominant cost variable. If a pump truck is required, that cost may exceed the cost of the concrete itself for a small slab.
Reinforcement
Wire mesh, rebar, or fiber is specified based on load and soil conditions. Reinforcement adds material cost that scales with slab area and specification.
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