The original helical pier was designed as a wooden shaft with an iron helix for use in lighthouse foundations. Nowadays,helical piers are one of the two most common types of structural piering devices for residential foundation applications in use today. Helical piers are an excellent choice for foundation repair and stabilization when light structural loads, unstable rock foundations or very deep load bearing stratums are present. Specification of hot dipped galvanized ground screw pile for greenhouse and fences  Shaft size 2 7/8″ Tubular-0.203″wall 2 7/8″ Tubular-0.262″wall 3 1/2″ Tubular-0.300″wall 4 1/2″ Tubular-0.337″wall 1 1/2″ Square Bar 1 3/4″ Square