Load measures the weight placed on a given surface in pounds. To know if too much load is resting on a surface, calculate the load per unit area. This tells you how many pounds per square inch (psi) is being applied to the surface, or the stress. If the stress exceeds the yield strength of the material, the material will break or deform.
Use a scale to determine the total weight, in pounds, of all objects on the surface. As an example, you might have five cement blocks resting on a hardwood floor in a stack. Assume each cement block weighs 9.07 Kilogram, so the total load is 20 times 5, or 45.4kg.
Measure the length and width, in inches, of the bottom of any object touching the loaded area. For example, the length and width of the bottom of the cement block might be 12 inches and 6 inches, respectively.
Multiply the length times the width to obtain the area of the object's bottom in square inches: 12 x 6 = 72. The area of the block touching the floor is 72 square inches.
Divide the load by the area to obtain the stress on the surface in psi: 100/72 = 1.4. The stress on the floor is 1.4 psi. The hardwood floor will not be damaged since the yield strength of wood is about 7,250 psi.