What are Screw Pile Caps?

In Calgary we can use screw pile foundations in many different applications.

All that is left above grade when a helical screw pile is installed into the soil is a small portion of the screw pile’s shaft. The screw pile shaft is a steel pipe and doesn’t offer much in the ability to connect to the structure of the pile that it’s meant to support. However the screw pile cap fits over this exposed portion of the screw pile shaft and serves as an adaptor or connector. This connection transfers the load of the supported structure to the helical pile. There are many different styles of screw piles caps and they allow screw piles to connect and support many different kinds of structures.

Standard Screw Pile Caps vs Custom Order and Fabrication

Four screw piles installed for concrete support

Generic Screw Pile Caps

There are some styles of screw pile caps that are so frequently used that they have been adopted by the construction industry as generic styles. These generic screw pile caps are often kept in stock and readily available from many different suppliers. This is because they are used to meet common applications like but not limited to lumber built structures, concrete grade beams, mobile homes and concrete slabs.

Custom pile cap for street light standard

Custom Fabricated Screw Pile Caps

Screw pile caps can be fabricated to meet the form and function of nearly any structural application. More specific applications require caps to be custom built to meet these unique design requirements. Mating a prefabricated object like a light standard or conforming to an engineer’s design are two situations where a custom fabrication would be needed.

What are the different types of generic screw piles caps?

8" Circular Flat Cap with slotted holes

Standard Flat Cap

The most common screw pile cap is the standard flat cap. These caps are included with most screw pile installations. Composed of a flat steel plate with slotted holes for fasteners, the flat cap can support many different types of structures. 

Flat caps are ideal for connecting to many different sizes of lumber beams and posts. Often used in backyard deck, shed and concrete slab applications. Also because these caps create a flat load bearing surface steel fabricated structures like mobile homes, sea cans and preformed stairs can also be connected to with standard flat caps.

It’s because of their very simple design and flat surface that the uses for these screw pile caps are endless.

Adjustable screw pile cap installed for a deck

Adjustable Flat Caps

In some cases the construction process can be made much easier if there is an allowance for vertical adjustment of a helical piling. Adjustable flat caps are the best option in this scenario. Composed of a flat plate similar to the standard flat cap but with a threaded portion that allows the cap’s height to be changed. ACME machine thread is used so the caps will not bind when being adjusted under load. A popular option for deck and garden shed construction as these caps can save time during the shimming and leveling process.

Screw Piles installed with offset flat caps in Calgary

Offset Flat Caps

The offset flat caps are nearly identical to that of the standard flat cap but with one important difference. Offset caps offer a small amount of horizontal adjustability for when certain situations arise. Just like the name indicates, the offset caps extend out from the centre line of the screw pile shaft. This off center sleeve allows the caps to be rotated on the screw pile shaft and change the horizontal position of the mounting surface in relation to the pile location. Sometimes a small amount of horizontal flexibility is needed. Proximity to utility lines or other structures can impede exactly where a helical screw pile can be installed and some lateral leeway is needed.

Screw Pile Cap with 15M rebar

Rebar Caps

Rebar caps are designed for use in concrete applications. More specifically rebar caps are used to transfer loads from concrete grade beams to screw piles. As the name implies, rebar caps have two pieces of 15M Rebar stock welded to the cap plate. Extending 6″ up these caps are then tied to the rest of the rebar reinforcement within the grade beam. With the screw piles installed under the grade beam and the rebar support tied together, concrete is then poured to tie the entire foundation system together. This makes for a very stable foundation that can be used to support garage walls and other roofed structures.

Connecting Structure To Deep Ground Foundations

The installation of one screw pile alone does not create a structural foundation system. It is the transfer of loads from the supported structure to each screw pile’s helix in the ground that provides the load bearing support system. Screw pile caps are the connection between the supported structure to the pile’s shaft which then transfers the load to the pile’s helix. All these screw pile components together provide a long lasting and stable deep ground foundation with endless structural applications.

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