A floating dock has to do two things at once: move freely up and down with the water, and stay exactly where it is against wind, current, waves and berthing boats. The anchoring system makes that possible. Marinas use four main methods: guide piles, telescoping piles, chain or elastic moorings, and stiff arms.
Floating dock anchoring methods compared
| Method | How it works | Best suited to |
|---|---|---|
| Guide piles | Piles are driven into the bed and the dock slides up and down on them | Most marinas where the bed suits pile driving |
| Telescoping piles | The pile extends and retracts with the water level | Marinas with visual obstruction requirements or large boat berths |
| Chain or Seaflex moorings | Chains or elastic lines hold the dock to anchors on the bed | Deep water, or remote sites where pile driving equipment is hard to bring in |
| Stiff arms | Rigid arms connect the dock to the shore or a fixed structure | Small projects where piles and moorings are not appropriate |
Guide piles
Piles are the most familiar way to anchor a floating dock in a marina. The dock is held by pile guides that let it travel up and down the pile as the water level changes. Piles are made of concrete or steel, with newer composite options, and the soil conditions and the materials available locally both affect the choice.
Steel piles can be left raw, painted with an epoxy coating or sleeved with HDPE. Our article on HDPE pile sleeves explains how sleeves protect a pile.
Telescoping piles
A telescoping pile extends and retracts as the water rises and falls. It suits marinas that have visual obstruction requirements, and berths for large boats.
Chain and Seaflex moorings
Where the water is too deep for piles, or the site is too remote to bring in pile driving equipment, a floating dock can be held by chains or by an elastic mooring system such as Seaflex, fixed to anchors on the bed.
Stiff arms
A stiff arm is a rigid arm that holds the dock off the shore or a fixed structure. It can suit small projects where neither piling nor a chain or elastic system is appropriate.
How engineers choose an anchoring system
- Water depth and how far the water level rises and falls.
- The bed: soil conditions decide whether piles can be driven and which type.
- Exposure: wind, waves and current set the loads the system must resist.
- Vessel size: larger boats put larger loads on the dock.
- Visual and permit requirements at the site.
- Access for pile driving equipment.
Anchoring is designed for each site. Bellingham Marine engineers the anchoring together with the floating dock system as part of its design-build service.
Frequently asked questions
What is the most common way to anchor a floating dock?
In marinas, guide piles are the most familiar method. Piles are driven into the bed and the dock slides up and down on them as the water level changes.
Can a floating dock be anchored in deep water?
Yes. In deep water a floating dock can be held by chains or an elastic mooring system such as Seaflex, fixed to anchors on the bed, instead of piles.
What is a Seaflex mooring?
Seaflex is an elastic mooring system. It holds a floating dock to anchors on the bed and is used in deep water or at remote sites where pile driving is difficult.
Have a site with deep water or a difficult bed? Ask Bellingham Marine which anchoring system fits.
