This process is intended for small non-structural repair or replacement of equipment with commercial projects where the building owner can obtain a permit to repair or replace the same or existing features of a building without architectural plans.
1 Mark the area that will need concrete and divide it into smaller areas. 2  Calculate its volume of the area after determining the shape of the area (see chart below) by multiplying in the height.  Convert the volume from feet to cubic yards to get the number of cubic yards of concrete youâll need.
Include the cost of gravel. For a 4-inch slab, you'll need the same amount of gravel you calculated for concrete, as the gravel bed will also be 4 inches deep. Use the same calculation to arrive at cubic yards of gravel, then multiply by 1.5 tons per cubic yard to get the number of tons you will need.oncrete is sold in cubic yards (27 square feet), so you will need to multiply your square footage from Step 1 by the depth of slab, then divide by 27. For example, a 10-foot-by-10-foot slab would require 1.3 yards of concrete. This is equal to [(10x10x.33 feet)/27].