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

Deciding between round shaft and square shaft helical piers depends on factors such as soil conditions, load requirements, and installation equipment.

### When to Use Round Shaft Helical Piers Round shaft piers are often preferred for challenging commercial and deep foundation projects due to their superior torsional strength and uniform geometry. You should choose round shafts when:

• High Torsional Strength is Required: The circular cross-section distributes shear stress evenly, making them ideal for high-torque advancement in dense till or weathered rock without premature yielding.
• Standard Soil Conditions are Granular: They displace less material in sandy or granular soils, preserving dense compaction for higher bearing capacity.
• Lateral and Uplift Loads are Present: Their uniform shape provides better resistance to lateral forces, which is beneficial for marine or slope-stabilization projects.
• Corrosion Resistance is a Priority: The smooth profile lacks exposed weld seams and crevices, allowing for a more uniform protective galvanization coating in aggressive or acidic soils.
• Small Equipment is Used: They can often be installed using lower-torque hydraulic drives mounted on skid-steers or mini-excavators.

### When to Use Square Shaft Helical Piers Square shafts are frequently used in residential and specific high-capacity industrial settings. You should choose square shafts when:

• Working in Cohesive Soils: In clay-heavy soils, the square profile provides greater surface area and superior torque transfer to develop capacity efficiently.
• Heavy Commercial Loads (Exceeding 100 Kips): Square shaft leads can offer higher torsional strength compared to round leads of equivalent steel weight, preventing shaft twist under extreme axial loads.
• Residential or Light-Commercial Use: They are common for standard residential applications like decks and home additions due to ease of handling.
• Field Modifications are Necessary: The geometry allows for easier on-site welding or rapid bolted/pinned connections in tight-access urban or interior retrofit projects.

Final selection should always be based on site-specific soil testing and geotechnical analysis performed by a structural engineer.