Building a deck... Pier Size / Loading Question
I'm not a expert but the answer likely depends on exactly where you live. When I built my deck in Maryland the footings needed to 30&quot; deep and 18&quot; in diameter (for the bottom 8&quot;).
See local ordinances for Howard County Maryland.
If you are lucky your jurisdiction may publish their requirements. If they don't publish them you could give your local permit office a call.
Jonathan