How much does it cost to lay a 20×20 slab?

On average, a 20×20 slab will cost around $2,500. The cost per square foot is between $4 and $8 on average. However, most property owners spend on average between $5.35 to $6.17 per square foot for both materials and installation.
The final number depends on slabs size, thickness, and any special reinforcement, e.g., wire mesh or rebar.