When should You Use Round Shaft Versus Square Shaft Helical Piers?

The choice between round shaft and square shaft helical piers depends on your project’s soil conditions, load requirements, and structural goals. Both designs serve as advanced earth anchoring systems, but they excel in different environments:

When to use Round Shaft Helical Piers:

• High-Load Commercial Projects: Round shafts offer superior torsional strength and uniform stress distribution, making them ideal for high-capacity foundations reaching axial loads exceeding 100 kips.
• Dense or Granular Soils: Their slender profile displaces less material, preserving dense compaction in sandy or granular soils. They also resist twisting better in dense till or weathered rock.
• Corrosion Concerns: Round shafts are often preferred for permanent foundations in aggressive soils or coastal zones because the continuous profile eliminates exposed weld seams where moisture can collect.
• Lateral and Uplift Loads: The uniform cross-section provides greater resistance to lateral forces, making them suitable for marine or slope-stabilization projects.

When to use Square Shaft Helical Piers:

• Residential or Light-Commercial Use: Square shafts are common for lighter structural loads, such as decks, home additions, and standard foundation repairs.
• Cohesive Soils (Clay): Square shafts provide greater surface area and superior torque transfer in clay, allowing them to develop capacity more efficiently through enhanced skin friction.
• Ease of Field Modification: Their geometry allows for easier on-site welding or pinning of extensions, which is beneficial for tight-access urban projects or interior retrofits.

Ultimately, the selection should be based on a site-specific geotechnical analysis and building code compliance using ICC-ES acceptance criteria AC358.