Pier, Caisson & Sonotube Concrete: Volume Formulas, Bell Footings, and Bag Counts
A drilled pier, caisson, or sonotube is a cylindrical concrete column installed below grade. This guide covers the volume formula for straight shafts, bell-bottom footings, and stepped piers — with worked examples for residential deck piers, sonotubes, and deep caissons — plus bag counts for common sizes.