The Helical Pier System consists of a 3″ diameter pipe helical pier and a steel strong back and is installed in sections from 3 to 10 feet in length. The strong back is normally a 6 or 8 inch steel channel that is bolted to the foundation wall. Installation normally occurs from the basement, where a 12″ hole must be cut into the concrete and the pier is installed by a hydraulically driven torque head. The torque head spins and screws the pier deep into the undisturbed soil and bedrock. The pier is installed at a angle normally around 10 to 20 degrees to insure the it is installed out of the Active Zone of Soil. The torque or force is measured during installation so that holding or tension forces can be determined. The steel strong back runs the height of the entire wall so that the holding force is spread equally into the foundation wall. The average length of installation 14 – 20 feet. Spacing of the strong backs depends upon the height of the foundation wall. Average spacing is 7 to 8 feet apart. Failures are extremely rare since the helical is anchored into undisturbed soils and the amount of force is measured and is calculated to meet the structural needs of the foundation wall.
