How to Choose the Right Ground Screw: Soil Conditions, Frost Depth, and Load Capacity
Ground screws are quickly becoming a popular alternative to traditional concrete foundations for decks, solar installations, fencing, pergolas, and small buildings. They install quickly, require minimal excavation, and allow construction to begin immediately after installation.
However, selecting the correct ground screw foundation is essential to ensure structural stability and long-term performance.
A ground screw is a fixed-length product, which means you select the size and length of ground screw you need based on: soil conditions, frost depth, and load capacity.
Soil Conditions and Ground Screw Performance
Soil type has a major impact on the load-bearing capacity of a ground screw foundation.
Common soil types include:
Dense clay
Compact gravel
Mixed soils
Sandy or loose soils
Dense soils typically provide higher resistance, allowing ground screws to support greater loads. Softer soils may require longer screws, a larger outside diameter ground screw, or additional screws to properly distribute the load.
Frost Depth and Why It Matters for Ground Screws
In colder regions, foundations must be installed below the local frost line to prevent frost heave.
Frost heave occurs when moisture in the soil freezes and expands, which can lift or shift foundations that are too shallow. When you install a ground screw, you always ensure that 2/3 of the threads are buried below the frostline to prevent heaving.
Load Capacity: Determining the Right Ground Screw Size
Every structure places a different load on its foundation system. Ground screws must be selected to safely support both vertical loads and uplift forces.
Key load considerations include:
Total weight of the structure
Snow loads
Wind uplift
Beam spacing and framing layout
Spacing between ground screws
Our foundation system from American Ground Screw is ICC Certified. The chart above is taken from page 13 of the ICC report and provides a reference for determining allowable loads for different ground screw installations.
Why Ground Screw Load Charts Matter
Using a verified load chart helps builders, engineers, and installers:
Select the correct ground screw length
Determine the number of screws required
Meet building code requirements
Ensure long-term structural stability
By evaluating soil conditions, frost depth, and load capacity, you can confidently choose the right ground screw system for your project.
Ground screw foundations offer a fast, durable, and environmentally friendly alternative to concrete. With proper planning and the help of engineered load charts, they can provide a reliable foundation solution for a wide range of projects.
*Montana Ground Screw is not a licensed engineering firm and does not provide structural or geotechnical engineering services.
