What Are Helical Piers?
Helical piers (also called helical piles or screw piles) are deep foundation elements made from steel shaft sections with one or more helical plates welded at intervals. Installation involves threading them into the ground with a hydraulic drive head - essentially a very powerful screwdriver.
As the pier is screwed deeper, resistance increases as it reaches more competent soil. Engineers calculate the minimum installation torque that confirms adequate bearing capacity. Additional shaft extensions are added as needed to reach the required depth.
How Helical Piers Are Installed
- Site layout - Pier locations are marked per the engineer’s or contractor’s plan. For perimeter work, access trenches are dug; for interior work, slab core holes are drilled.
- Lead section installation - The lead section (with helical plates) is connected to the drive head and advanced into the ground.
- Extension sections - Plain pipe extensions are added as the lead advances, extending the pier to required depth.
- Torque monitoring - Installation torque is monitored throughout and logged. Installation stops when minimum torque is achieved.
- Bracket installation - A foundation bracket is welded or bolted to the pier shaft and attached to the foundation footing.
- Lifting - Hydraulic jacks at each pier position simultaneously apply load to lift the structure toward target grade.
- Lock-off - Load is locked into the bracket. Slab patches and access pits are completed.
When Helical Piers Are the Right Choice
Helical piers are preferred over push piers in several specific situations:
Interior slab piers: Push piers require substantial dead load as reaction - interior slab areas carry less load than the perimeter footing. Helical piers can be installed from below through core holes without needing the structure’s weight as reaction.
Lighter structures: Detached garages, additions, sunrooms, and lighter residential structures don’t provide enough dead load for push pier installation. Helical piers screw in independently of the structure load.
Limited access: Helical pier drive heads are compact. They can work in tight crawlspace clearances, basements, and locations where larger equipment cannot access.
Tension applications: Helical piers resist both compression (pushing down) and tension (pulling up) loads due to the helical plate geometry. This makes them suitable for wall tiebacks and retaining wall stabilization, where push piers are not appropriate.
Sensitive structures: Helical installation produces less vibration than driven piers, making them preferable near historical structures, sensitive equipment, or existing utilities.
Helical Pier Specifications
A helical pier system includes:
- Material: High-strength steel (typically ASTM A36 or A513)
- Corrosion protection: Hot-dip galvanizing (recommended) or fusion-bonded epoxy coating
- Shaft diameter: 1.5” - 3” square bar or 2.875” - 4.5” round pipe, depending on design load
- Helix configuration: Single helix for most residential; multi-helix for higher loads
- Bracket: Load transfer bracket matched to the footing configuration
Ask the contractor for the pier manufacturer’s ICC-ESR evaluation report - this is the industry-standard third-party validation of load capacity for the specific pier system being used.
Helical Pier Cost
| Cost Item | Range |
|---|---|
| Per pier installed (materials + labor) | $1,200 - $3,500 |
| Typical residential project (6-10 piers) | $8,000 - $25,000 |
| Interior core drilling | $150 - $400 per hole |
| Crawlspace installation premium | +10-20% for low clearance |
Helical piers typically cost 10-20% more per pier than comparable push piers because of the more complex manufacturing (helical plate welding) and slower installation (screwing vs. driving). However, for projects where helical piers are the appropriate system, this premium is unavoidable.