A Complete Guide to Helical Piers

What Are Helical Piers?

Helical piers – also referred to as helical piles, screw piles, screw piers, screw anchors, helical anchors, and helical screw piles – are foundation piers that look something like giant corkscrews. They’re used to strengthen and stabilize residential and commercial structures with problems due to differential settlement. The piers transfer the structure’s load to soil that can support it.

Helical piers are mainly used for new construction projects requiring a deep foundation system because the soil is less than ideal. However, helical piers are also used to stabilize existing foundations.

There are two types of helical piers: round shaft, and square shaft. The one used depends on the situation.

How Do Helical Piers Work?

Helical piers are turned into the soil until they reach the necessary depth or torque requirement. (A geotechnical engineer determines this.) The depth is usually somewhere between 10 and 30 feet. However, they can be installed up to 150 feet deep if required.

Helical piers come in various configurations and sizes. Geotechnical engineers determine which type to use based on a soil report. This is because the diameter of the helix depends on the type of soil. For example, larger helices will be necessary if the soil is rich in clay. Also, a helical pier might need more than one helix in certain situations.

When Are Helical Piers Used?

Helical piers are used when a new construction project requires a deep foundation system because of problematic soils and when an existing structure needs stabilization because of differential settlement. We’ll talk more about differential settlement in just a bit.

Helical piers are suitable for use in either seismically active, environmentally sensitive areas, or with a high groundwater level. The stability of helical piers can be increased by using multiple bearing plates.

Differential settlement is caused by various things, including:

• Poor compaction – Soil needs to be correctly tamped down before anything gets built on top of it. If this isn’t done during construction prep, the structure could settle unevenly into the soil after it’s built.
• Expansive soil – This is clay-rich soil that expands when it absorbs moisture and then shrinks when it dries out. This back-and-forth swelling and shrinking creates movement in the ground under the foundation and can lead to differential settlement.
• Soil erosion – Erosion-prone soil could lead to the formation of voids under the foundation. When the structure settles into the voids, you have differential settlement.
• Excavation next door – Heavy excavation can destabilize the soil under nearby structures leading to differential settlement.
• Earthquakes – We probably don’t need to explain how seismic activity can lead to structural problems.

• Uneven floors – The unevenness might be so slight you don’t even notice it at first.
• Stair step cracks in brick or masonry – This is a sure sign of differential settlement and foundation damage
• Windows and doors that no longer open and close properly – If the problem is limited to one window or door, it might not be a foundation problem. However, problems with multiple windows and doors indicate a foundation issue.
• Cracks in walls, ceilings, and floors
• Bowed walls, with or without cracking
• Ceilings and floors that have separated from the wall – Even slight separations can indicate a problem.
• Drywall cracks or nail pops
• Torn wallpaper – This might indicate the wall behind the wallpaper is cracked.
• Moldings that are separating from the wall or ceiling
• Chimneys and porches that lean away from the house