Helical Piers

  • Helical Piers are galvanized steel shafts with several high-strength helices welded on; securely coupled sectional segments are rotated into the ground at a desired angle providing end-bearing vertical or lateral foundation support reaching competent soil or bedrock
  • Helical foundation systems are ideal foundation alternative for weak soils, expansive soils, high ground-water projects, hillsides, creeksides, bay mud
  • Helical Piers are also ideal for sites with sensitive environmental and logistical concerns, including projects requiring minimal site disturbance, removable structures, contaminated soils conditions
  • Drill cuttings, needs for soils stockpiling, moving, disposal and casing are eliminated; traffic, noise & vibration reduced significantly; installation can be with potable equipment in basements & landlocked yards
  • In weathered rock (such as Franciscan formation), use of helical piers and tie-backs allow significant reduction in traditional embedment into the rock saving time & cost for foundation work
  • An innovative solution to retaining wall design in a sensitive environment, such as creek banks - see www.GreenRetainingWall.com

Selected Projects

  • Mill Valley,
    New House

  • Golden Gate Heights,
    House Addition

  • Lower Pacific Heights,
    House Addition

  • Mill Valley,
    Hillside Retaining Walls

  • Berkeley Hills,
    House Renovations & Foundations Retrofit

  • Mill Valley,
    Selective Foundation Retrofit

  • San Rafael,
    Selective Foundation Retrofit

All projects accomplished in close cooperation with Chris Baumsteiger of C.R. Baumsteiger Construction Inc., an authorized AB Chance installer for 18 years, who speciales in helical foundation systems.

Product Manufacturer, History, Approvals

Helical piers & accessories are manufactured by A.B. Chance Company, www.abchance.com, a division of Hubbell Power Systems. Helical systems were first introduced nearly a century ago as an ingenious element of power line support in poor soils and rough terrain. In the last few decades, helical foundation systems have found an increasingly wide use in foundation construction/retrofit in residential, commercial and infrastructure projects. Helical piers are ICBO-approved and have now been used in thousands of projects throughout California. Helical foundations are familiar to most building officials in the Bay Area as they brought new levels of efficiency of foundation construction, especially for retrofit work and in emergency situations such as landslides.

Engineering, Quality Control & Testing

In accordance with shear strength theory of Soils Mechanics, soils bearing strength is proportionate to soils shear strength, which in turn is proportionate to the torque needed to advance a helical screw anchor. Installation torque is monitored by measuring the pressure in the oil hose that powers the torque motor. An empirical coefficient between the torque and the bearing capacity has been developed for most soils, which is now part of accepted civil engineering science. Factor Of Safety appropriate to the project conditions is used to ensure that the installed pier capacity is FOS times higher than the calculated-load capacity.

For further quality control, we specify selective testing in projects that are designed for new loads, i.e. new construction and additions. As testing is fairly expensive, we generally do not require testing for volunteer retrofits. For projects that do require testing, we have developed a simplified pull test procedure. As pier withdrawal capacity is presumed to be less than the pier vertical load capacity, the passing of a pull test ensures adequate pier load bearing. (Footnote: empirical and theoretical research prove that pier shaft buckling does not occur even in weak soils due to lateral restraint of soil mass surrounding the pier). A.B. Chance web site and product catalog provide more technical details, specifications, and engineering support.

Not all projects, however, are best suited for helical piers. For example, in bedrock, augering or rock anchors may be preferable as helical penetration may not be practical. For conventional footings, helical piers may not be competitive. At Optimal, we carefully evaluate foundation alternatives from the cost and procedure standpoint.