Footing Clarification Question

[Ross R]

John,
Quick question - when digging holes for a post / pier foundation. 

Do you dig 8 inch holes with at least a 16 inch high footing of cement or crushed rock?

Or is it a 16 inch hole with a 8 inch high footing of crushed rock / cement at the bottom.

Thanks
Ross

[MountainDon]

The norm is to have a hole that provides the larger footprint to spread weight out more and to make a concrete pad thickness about half of that. The size is determined by the soil's ability to support a load with no movement.

If you are in an area with building codes and inspections your local governing agency will have recommendations suitable to your climate and soil type.

Keep in mind that a circular concrete footing of 16 inch diameter has about 78% (3/4 for rough figuring)  of the surface area of a 16 inch square concrete pad.