Coastal Services Center

Dock Support Systems

What's a Pile?

Dock piles or pilings are heavy beams of timber, concrete, or steel driven into the earth to support the walkway of a dock. Dock piles vary in size from 4-by-4-inch posts to 10-to-12-inch diameter posts as thick as telephone poles. Pressure-treated wood that resists rotting is by far the most common material used for residential dock piles.

Piling Systems

Two piling systems are used to support fixed docks: double piles and monopiles.

Double piles are the most common. In double pile systems, smaller piles are located at both edges of a walkway to support its weight. Cross-bracing may or may not be required.

Monopiles are generally less noticeable in scenic vistas and may have less impact on underwater habitat. In a monopile system, a single, larger pile supports the center of the walkway. Cross-bracing from the single pile supports the edges of the walkway.

In the Scenarios

Monopiles are used only in Scenario B. The monopiles shown are 10 to 12 inches in diameter.