Building Boats, Vessels and Floating Structures: A Practical Guide

Types of Vessels: The Big Picture

Commercial and private vessels fall into a few broad families. Within each family, size, hull shape and equipment vary enormously, but the basic purpose defines most of the design decisions.

Main vessel families

Hull Materials: Aluminium, Steel, Composite or Plastic

The hull material decides weight, strength, maintenance, service life and a large share of the price. There is no universally best material, only the right one for a given size, workload and operating area.

Where Vessels Are Used

Almost every coastal industry depends on vessels. Below are the main areas and the vessel types that usually serve them.

• Aquaculture: service vessels, feed barges, landing craft, small PE boats for daily inspection rounds.
• Construction and civil works: barges, crane pontoons, landing craft, tugs for bridge, quay and pipeline projects.
• Offshore energy and wind: crew transfer vessels, supply boats, survey vessels.
• Transport to islands: landing craft, small ferries, water taxis, cargo workboats.
• Ports and harbours: tugs, pilot boats, pontoons, oil-spill response boats.
• Tourism and hospitality: passenger boats, floating saunas, cafés, event platforms and fjord sightseeing vessels.
• Housing and private use: houseboats, floating cabins, private jetties and boathouses on pontoons.
• Public services: rescue, police, customs and environmental monitoring vessels.

How to Choose a Workboat

A workboat is the most versatile vessel on the coast, and that is exactly why it is easy to order the wrong one. A boat that is perfect for carrying passengers can be useless for crane work, and a heavy crane boat can be slow and expensive on long transits. Start from the job, not from a catalogue.

What to look for

• Clear main task: define what the boat will do 80% of the time: cargo, crane lifts, towing, passengers or survey.
• Deck area and payload: measure the largest item you will carry and add margin. Deck space is almost impossible to add later.
• Crane capacity and reach: lifting capacity drops with reach. Size the crane for the heaviest lift at the distance you actually need.
• Seakeeping for your area: sheltered fjord work and exposed coast need very different hull forms and freeboard.
• Oversized engines "just in case": extra power raises purchase price, fuel consumption and emissions without helping a slow working boat.
• Copying a second-hand design blindly: an older design may not meet today's regulations or your operating profile.

Common workboat configurations

1. Open deck with deck crane

   The most flexible layout. Wheelhouse forward, large deck aft, knuckle-boom crane. Handles cargo, moorings and equipment. The default choice for coastal contractors.

2. Landing craft with bow ramp

   For moving vehicles and machines to places without a quay. Flat bottom, ramp forward, wheelhouse aft. Less comfortable in waves, unbeatable for beach access.

3. Catamaran workboat

   Two hulls give a wide, very stable deck and good speed. Popular for aquaculture and crew transfer. More expensive to build and needs wider berths.

4. Push and tow boat

   Compact hull, maximum thrust, strong towing point. Used together with barges and pontoons that have no propulsion of their own.

5. Survey and inspection boat

   Smaller, quieter and fuel-efficient, with space for sensors, a moon pool or ROV handling. For mapping, diving support and inspections.

Practical tips

• Write down your three most demanding jobs and let them set the minimum specification.
• Check berth length, draught limits and slipway size in the harbours you use before fixing the dimensions.
• Plan the working deck together with the people who will use it: tie-down points, rails, lighting and drainage matter every day.
• Ask early which rules apply to your vessel's length and use. The requirements affect layout, safety equipment and cost.
• Think about resale: a well-documented, standard-layout workboat keeps its value better than a highly specialised one.

How to Choose a Vessel for Aquaculture

Fish farming is one of the toughest operating environments for a small vessel: daily work in all seasons, heavy lifts over the side, constant contact with pens and moorings, and exposure to wind and waves at outer locations. Stability and deck equipment matter more than speed.

What to look for

• Stability during side lifts: the vessel must stay safe when the crane lifts nets or anchors far out over the side.
• Winches and cranes sized for the site: pen size, mooring dimensions and water depth define the required capacity.
• Robust fendering and hull: the boat will touch pens, feed barges and other vessels many times a day.
• Good working light and visibility: much of the year the work happens in darkness.
• Planing hulls for heavy work: fast hulls lose stability and efficiency when loaded and working at low speed.
• Underestimating crew facilities: heating, mess and toilet on board keep crews productive through long winter days.

Typical aquaculture vessels

1. Service catamaran

   Wide, stable deck with cranes and winches for net changes, mooring work and heavy equipment. The workhorse of larger farms.

2. Feed barge

   Moored at the site, stores feed and runs the feeding system. Steel or concrete hull, with generators, control room and crew areas.

3. Landing craft

   Carries machines, containers and materials between shore base and site. Useful for farms far from a proper quay.

4. Small PE or aluminium boat

   For daily inspections, small repairs and staff transport between pens. Cheap to run and nearly indestructible.

Practical tips

• Map the exposure of your locations: a vessel for sheltered sites can be lighter and cheaper than one for open-sea farms.
• Standardise equipment across the fleet so crews and spare parts can move between vessels.
• Consider hybrid or electric drive: short trips and long idle periods near the pens suit batteries well.
• Leave space and power for future equipment such as cleaning systems or sensors.

How to Choose a Barge or Pontoon

Barges and pontoons look simple, but they carry some of the heaviest and most valuable loads on the water: cranes, machines, construction materials, sometimes entire buildings. Getting the dimensions, buoyancy and deck strength right is essential.

What to look for

• Deck load per square metre: not only total payload counts, but also point loads from crane outriggers and tracked machines.
• Freeboard when loaded: enough height above water to stay safe in waves and wake from passing ships.
• Transport and assembly: modular pontoons that fit on a truck can be moved between sites; large hulls may need towing.
• Mooring and anchoring: spud legs, anchors or fixed moorings depend on depth, seabed and how long the barge stays.
• Using a transport barge as a crane platform without calculation: crane work creates heeling moments that need specific stability checks.
• Ignoring corrosion and ice: steel pontoons need protection, and ice can damage light floats.

Common types

1. Flat-deck cargo barge

   Steel hull with a strong open deck. Carries materials, containers and machines, pushed or towed by a workboat.

2. Crane pontoon

   Barge designed as a stable base for a crane or excavator, often with spud legs to hold position during work.

3. Modular pontoon system

   Bolt-together sections in steel, aluminium or plastic. Flexible size, easy to transport, reusable on new projects.

4. Marina and jetty pontoons

   Concrete or aluminium floats with decking for boat berths, walkways and private jetties. Designed for comfort and long life.

5. Floating dock

   Can be partly submerged to lift boats out of the water for maintenance. A specialised solution for yards and larger marinas.

Practical tips

• List every load the barge will carry, including the heaviest machine and the worst combination, before choosing size.
• Check how the barge will reach the site: road transport limits, towing distance and weather windows.
• For long-term installations, plan inspection and maintenance access from the start.
• If the pontoon will be used by the public, expect stricter requirements for railings, lighting and rescue equipment.

How to Plan a Floating Building

Floating homes, cabins, offices and saunas are growing in popularity along coasts, lakes and city waterfronts. They combine two disciplines: building design and floating structure engineering. The building must be pleasant to use, and the hull must keep it level, dry and safe for decades.

What to look for

• Weight and balance: every wall, bathroom and stove affects trim. The building layout and hull must be designed together.
• Permits and location: mooring a building on the water usually needs approval from the municipality and the harbour authority. Check this before designing.
• Utilities: electricity, fresh water, wastewater and heating must be solved safely for a floating installation.
• Durable hull: concrete and steel hulls give stability and long life; lighter floats suit small saunas and cabins.
• A standard house on floats: ordinary building methods ignore movement, moisture and weight limits on the water.
• Forgetting winter: ice, snow load and storms must be part of the design in northern waters.

Popular floating projects

1. Floating sauna

   Compact, relatively affordable and very popular. Wood-fired or electric heater, terrace and ladder for a swim. Can be stationary or towable.

2. Floating cabin or holiday home

   A small living unit with kitchen and bathroom, moored in a sheltered spot. Needs a solution for water and waste.

3. Houseboat

   A permanent home on the water, often on a concrete hull in a city harbour. Comfort and insulation comparable to a house on land.

4. Floating café, office or event space

   Commercial buildings for waterfronts. Higher requirements for fire safety, escape routes and accessibility.

Practical tips

• Secure the mooring site and permit first. A beautiful design without a legal place to lie is a costly mistake.
• Choose light but durable interior materials to save weight and keep the building level.
• Plan ventilation well: moisture from the water and from use is the main enemy of floating buildings.
• If the unit must be moved later, design it to fit transport and towing limits.

Diesel, Hybrid or Electric Propulsion

Propulsion is one of the biggest decisions in a new build. It affects purchase price, running cost, noise, emissions and which ports and fjords the vessel can operate in over its lifetime. Electrification is advancing quickly, especially for vessels with short, predictable routes.

A good rule of thumb: the more time a vessel spends idling, manoeuvring or on short fixed routes, the stronger the case for batteries. The more time it spends on long, unpredictable transits, the stronger the case for diesel or hybrid. Public support schemes for low-emission vessels can change the calculation significantly, so they are worth checking before deciding.

What Drives the Cost of a New Build

The most common question we hear is "how much does a boat like this cost?" The honest answer is that two vessels of the same length can differ in price several times over. These are the factors that make the difference.

• Size and weight: length is a rough guide, but steel or aluminium weight and deck area drive material and labour.
• Hull material: aluminium costs more per kilo than steel, but saves on weight, fuel and maintenance.
• Propulsion: electric and hybrid systems add significantly to the price, while lowering running costs.
• Deck equipment: cranes, winches, A-frames and hydraulics can be a large share of the total budget.
• Rules and certification: the vessel's length, use and operating area decide which requirements, approvals and inspections apply.
• Interior and comfort: wheelhouse electronics, cabins, heating and insulation vary from basic to high-end.
• Design work: a proven design adapted to your needs is cheaper than a fully custom one.
• Yard, timing and location: yard capacity, delivery time and transport to your site all affect the final price.

This is why a serious estimate starts with the operating profile, not a price list. Once the main task, operating area, payload and propulsion are clear, the budget can be calculated with far more precision, and you avoid paying for things you do not need.

How a Vessel Project Runs

Most new builds follow the same sequence. Knowing it helps you plan time, money and decisions in the right order.

1. Needs and operating profile

   What the vessel will do, where, how often, with how many people and which loads. This is the foundation for everything else.

2. Concept and budget estimate

   Main dimensions, hull material, propulsion and key equipment are chosen, and a first cost range is calculated.

3. Design and documentation

   Drawings, stability and strength calculations, equipment lists and specifications for the yard.

4. Approvals

   Depending on the vessel, drawings and documentation are reviewed by the maritime authority or a classification society, and floating buildings may need local permits.

5. Yard selection and contract

   Offers from yards are compared on price, delivery time, quality and references, and the build contract is agreed.

6. Construction and follow-up

   The build is monitored against the specification, with inspections at key stages.

7. Sea trials and delivery

   Tests, final inspection, documentation handover and training of the crew.

Questions and Answers

Get a Consultation and a Cost Estimate

If you are planning a boat, vessel or floating structure and are not sure which type, material or propulsion is right, write to us. We will help you define the project, choose a sensible solution and calculate what it will cost.