Decision guide · 6 min
Fixed pier or floating concrete pontoon?
Published:
Short answer: A floating reinforced concrete pontoon is usually the better fit on reservoirs and lakes with a large seasonal water level range, in deep water and where the bed does not suit piling. A fixed pier on piles is the stronger choice for heavy deck loads such as trucks and cranes, in shallow water with pileable ground and where the level barely changes. Decide with measured water levels, bathymetry, soil, wave and load data.
What is the fundamental difference?
On a fixed pier the deck sits on piles that are driven or bored into the bed, so its level never changes. Loads travel through the piles straight into the ground; when the water rises or falls, the pier stays put and only the gap between deck and water surface changes.
A floating pier is carried by the buoyancy of reinforced concrete pontoons. The pontoon rises and falls with the water, and the height of the deck above the waterline, the freeboard, depends on the load it carries. Its position is held by chain and concrete block moorings or by pile guides, and a gangway that absorbs the level difference links it to the shore. At heart, the choice is whether the load goes into the ground or into the water.
Water level range: the reservoir and lake case
The most influential input is the difference between the lowest and highest water level expected during operation. On dam reservoirs the level can change markedly with season, rainfall and water use, and some natural lakes show a similar seasonal swing. If a fixed deck is set for high water, a step that is hard to bridge opens up between deck and boat as the water drops, and intermediate landings, stairs or ramps become necessary.
A floating pontoon absorbs the range by moving with it, so boarding height stays the same at every level. The design focus shifts to the gangway: the larger the range, the steeper the gangway becomes, and the longer it must be to keep an acceptable slope. On sheltered water with little level change, this drawback of a fixed pier largely disappears.
Do depth and bed conditions allow piling?
The feasibility of a fixed pier starts with its piles. As the water deepens, the free length of each pile and its buckling risk grow, and so does the marine plant needed to install it. In soft, muddy beds lateral pile capacity drops and piles must be longer to reach a bearing layer; on rock, drilling may be needed instead of driving. Each of these conditions feeds straight into cost and programme.
For a floating pier the bed carries no structural load, and on deep sites with soft ground chain and concrete block moorings are often the more practical route. The trade-off is that enough depth must remain under the pontoon at the lowest water level, or it will ground. Both options need a bathymetric survey and a bed investigation before the decision; without them, any choice rests on assumptions.
Wave exposure and deck loads
The two systems respond to waves differently. A fixed pier does not move; wave forces act on the piles, and the deck is kept high enough that waves do not strike its underside. A floating pontoon moves with the water; the mass of a concrete hull limits motion, but in high or long-period waves comfort drops and connection and mooring forces rise. On exposed sites a floating layout is assessed together with a breakwater that shelters the basin. Wind actions on both are taken from TS EN 1991-1-4, the Eurocode part on wind.
Deck load also weighs heavily in the choice. Trucks, mobile cranes and forklifts put wheel and point loads directly into the piles of a fixed deck. On a floating deck every added load increases draft, and loads near an edge cause heel, so regular vehicle access and crane work favour a fixed structure.
Construction method, programme and maintenance
Most of the work on a fixed pier happens over water: barge-mounted cranes and piling rigs, pile installation, pile caps and deck. All of it depends on weather and sea state, and lost days stretch the programme. For a floating pier the modules are cast under factory conditions while the moorings and shore connection are prepared on site; over-water work is limited to launching, joining and mooring. Road transport of heavy modules, crane capacity and a launching point must be planned early.
In service, the most severe exposure on a fixed pier is on the part of each pile that is repeatedly wetted and dried. A concrete pontoon hull in seawater is designed to exposure classes XS1–XS3 of TS EN 206, the European concrete standard; maintenance concentrates on connectors, fenders, chains and guide hardware. Floating modules can also be rearranged, and the pier extended in stages.
Permits, supply and a decision checklist
In Turkey, permitting for both fixed and floating piers is subject to Law No. 3621, the Turkish Coastal Law, and its secondary legislation; the approvals needed depend on location and use. The permit file should be opened at the start, whichever system is chosen.
Onshore infrastructure elements such as retaining walls, U-channels, culverts and kerbs, and land buildings framed with precast columns, roof beams and façade panels, are part of the BETTON PREFABRİK range. Bring these inputs to the decision meeting: lowest and highest water level, bathymetry, bed investigation, wave and wind data, deck loads and vehicle access needs.
Frequently asked questions
- Fixed or floating pier on a dam reservoir?
- On reservoirs where the water level changes markedly with the seasons, a floating reinforced concrete pier is usually the better fit because boarding height stays constant. A fixed deck is left standing high as the water drops. The final choice weighs the lowest and highest levels, depth at low water and gangway geometry together.
- Can vehicles drive onto a floating pier?
- Only if the pier is designed for it. Vehicle weight increases the pontoon's draft and causes heel as it nears an edge, so pontoon size, freeboard and gangway are all sized for that load. With frequent truck traffic, mobile cranes or heavy point loads, a fixed pier on piles is generally the more practical option.
- Can piles be driven into any seabed?
- No. Soft, muddy beds reduce lateral pile capacity, rock may call for drilling instead of driving, and deep water increases pile length and plant requirements. Feasibility is confirmed with a bathymetric survey and a bed investigation; where conditions are unfavourable, a floating system with chain and concrete block moorings is assessed instead.
- What permits does a pier need in Turkey?
- Fixed and floating piers on sea and lake shores in Turkey are subject to Law No. 3621, the Coastal Law, and its secondary legislation. The approvals required vary with location and intended use, so the permit application should run in parallel with choosing the system and fixing the layout.
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