The average cost of a 20×20 concrete slab is based on the average price of a six-inch slab. If you choose a four-inch slab, you may save up to $0.74 per square foot. The edges of the concrete slab can also be thickened to increase the strength of the foundation. With 12-inch-thick edges, you pay another $1 per square foot.

The short answer to the question “How much does a 20×20 concrete slab cost?” is somewhere between $1,600 and $3,200, based on estimates which show the cost of barndo foundations ranging from $4 to $8 per square foot. However, there are a number of different factors which can affect the overall cost.

While it’s going to cost between $4 to $8 per square foot to have new concrete installed. If you already have an existing pad, sidewalk or patio in place that needs replacement, expect to pay an extra $2.50 – $5.00 per square foot for demolition and disposal.