What are Screw Pile Caps
Screw pile caps are attachments placed on top of screw piles, which are a type of deep foundation ground screw used to support structures such as buildings, bridges, and piers. These caps are crucial for distributing the load from the structure into the screw piles, thereby enhancing stability and strength.
Screw piles are long steel shafts with helical flanges or blades that are screwed into the ground, designed for quick installation and immediate load-bearing capacity. The caps, typically made of steel or are attached to the upper end of these piles and much like an adaptor provide a secure connection point for the structure above.
The design and material of a screw pile cap can vary depending on the application and load requirements. Some caps are adjustable to ensure proper alignment with the structural components they support. These caps are essential for ensuring the foundation system’s long-term performance and safety.
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How Do Screw Pile Caps Attach?
Screw pile caps are manufactured in various shapes and designs to align with the load of the primary structure they support. Acting like a structural adaptor, screw pile caps connect the supported structure to the helical pile’s shaft. This setup transfers the load from the structure to the screw pile cap, then to the pile shaft, and finally into the ground through the screw pile’s helix.
In some cases, pile caps can rest on the pile shaft under gravity alone. However, in scenarios where uplift loads are a concern, caps may be bolted or even welded for added stability in high-stress applications.
Types of Pile Caps & Their Applications
Standard Flat Cap
The standard flat cap is the most frequently used pile cap due to its straightforward design. As the name suggests, a flat cap is a flat plate with pre-drilled bolt holes that sits on top of a screw pile’s shaft. Its simplicity allows it to be bolted or welded to any primary structure the screw pile is intended to support.
Moreover, flat caps are ideal for supporting sidewalks, driveways, and concrete slabs because of their low profile.
Adjustable Pile Caps
Adjustable Screw Pile Caps feature a threaded shaft, allowing for height adjustments by extending the threaded portion of the cap. Although various designs exist, most adjustable caps require unloading the structure and rotating a non-fixed base plate up or down along the threaded section. The main drawback of these caps is their limited use in light-duty applications due to the reduced structural strength of the threaded area.
Adjustable caps are commonly used for uncovered decks. They simplify deck construction by supporting laminated deck beams without the need to cut vertical posts to size. Additionally, the deck’s height can be adjusted after construction to fine-tune the drainage angle or correct the deck’s height if the attached home settles over time.
Post Support Saddle Bracket Cap
The saddle bracket cap features a “U” shaped bracket designed to hold up to a 6-inch wooden post. These caps are particularly useful for connecting wooden structures supported by posts or beams, such as decks, pergolas or three-season rooms. The upright sections of the bracket are pre-drilled, allowing lag bolts to securely fasten the wooden post to the pile cap.
Rebar Pile Caps
Designed specifically for concrete-grade beams, the rebar pile cap features angled rebar extending from the top of the cap plate. Rebar tie wire can be used to connect the reinforcing bars that are poured within the grade beam. Concrete-grade beams are nothing new in construction, but using helical piles with them is a positive construction trend that is growing. The rebar pile cap encased within the concrete of the grade beam creates a solid connection with the grade beam that not only holds the grade beam but also allows for the perfect transfer of a building load down into the supporting soil deep in the ground.
Custom Fabrication
Generic screw pile caps can support most structural applications, but in some cases, unique requirements necessitate a custom-fabricated cap. Fortunately, our manufacturers can create custom pile caps to match almost any specified shape and load capacity. The downside to custom caps is the potential for higher costs and longer lead times. However, in certain situations, having the correct custom-made pile cap is well worth the investment.
Have Questions?
If you are unsure about which generic screw pile cap is best for your construction project or if you think you may require custom-fabricated pile caps, contact the Edmonton Screw Pile Pros and feel free to ask. Our team has seen it all and can happily answer any questions you may have.