Flagstone Prices. The national average cost of flagstone is $15 to $20 per square foot. This price includes the base material, mortar and labor. The average cost for the stone alone runs along $2 to $3 per square foot.What is Pennsylvania stone?
Pennsylvania Bluestone is a layered sandstone found only in the northeastern tier of Pennsylvania, parts of northern New Jersey and the southern tier of New York. The quarried product has many uses, from cut dimensional stone used in patios, walkways and stair treads to architectural stone used in buildings.