Not every shipment fits neatly inside a standard container. Wind-turbine blades, transformers, cranes, pressure vessels, yachts and industrial plant routinely exceed the dimensions or weight limits of a 20ft or 40ft box. Moving this kind of freight is a specialised discipline known as project cargo, out-of-gauge (OOG) and breakbulk shipping. This guide explains the equipment, the engineering and the paperwork involved, and when each method makes sense.
What counts as OOG, breakbulk and project cargo?
The terms overlap, but they describe different things:
- Out-of-gauge (OOG) cargo still travels on a container vessel, but it is too tall, wide or long to fit inside a closed box. It rides on a flat-rack or open-top and protrudes beyond the container's profile.
- Breakbulk is cargo loaded directly into a vessel's hold as individual pieces or bundles, not containerised at all — steel coils, machinery, pipes, project modules.
- Project cargo is the umbrella term for large, complex, high-value moves — often a mix of OOG, breakbulk and heavy-lift pieces shipped together as one engineered campaign.
Special equipment: flat-racks and open-tops
For cargo that exceeds standard container dimensions but is still manageable, two units handle most jobs:
- Flat-rack containers have a base and two collapsible end-walls but no sides or roof. They suit heavy, wide or oddly shaped loads — transformers, boats, vehicles, machinery — that can be lashed down from the sides. Loads can overhang the ends and sides (OOG).
- Open-top containers have solid walls but a removable tarpaulin roof, so tall cargo can be craned in from above. Ideal for items that exceed the 2.39m internal height of a standard box.
When cargo genuinely fits a closed box, it is cheaper and simpler to ship as ocean freight in standard equipment — so always confirm true dimensions before defaulting to special gear. If your consignment is borderline, compare the trade-offs in our FCL vs LCL guide before booking flat-racks.
Breakbulk and heavy-lift vessels
When a piece is too big or too heavy even for a flat-rack — say a 200-tonne generator or a 40-metre tower section — it moves as breakbulk on a multi-purpose or heavy-lift vessel. These ships carry their own cranes, often rated from 100 up to several hundred tonnes, and have wide, unobstructed holds and strengthened tween decks. Heavy-lift specialists may also use tandem lifts (two cranes working together) or roll the cargo aboard. For wheeled or tracked units, roll-on/roll-off can be more efficient — see our RoRo vehicle shipping guide.
Lifting, lashing and securing
Securing heavy and oversized cargo is an engineering exercise, not guesswork:
- Lifting plans specify rigging, spreader bars, sling angles and lift points so the load is never overstressed.
- Lashing and stowage follow the vessel's Cargo Securing Manual and IMO rules, using chains, turnbuckles, welded stoppers and timber dunnage to resist roll, pitch and heave at sea.
- Centre of gravity and weight distribution must be calculated and marked, because an incorrectly slung load can shift in transit.
Surveys and route surveys
Two kinds of survey protect a project shipment. A cargo survey records the condition and dimensions of the piece before loading and on arrival, which is vital for any insurance claim. A route survey (or transport-engineering study) checks the inland legs: road widths, bridge clearances, axle-load limits, roundabouts, overhead cables and port crane capacity. For a heavy module, the route survey often dictates the whole plan — there is no point booking a vessel if the cargo cannot reach the quay.
Because the stakes are high, marine cargo insurance is not optional on project moves. Read our cargo insurance basics guide to understand all-risks cover, general average and how to value a one-off piece.
Costs, surcharges and Incoterms
OOG and breakbulk pricing is quoted per shipment, not from a tariff, because every move is engineered. Expect charges for crane hire, extra lashing, OOG slot premiums on container vessels, and port handling for non-standard pieces. Fuel and currency surcharges still apply — our guide to BAF, CAF and THC explains the recurring add-ons. Because responsibility for lifting and securing can shift between buyer and seller, agree your Incoterms 2020 carefully; FCA or DAP often suit project moves better than EXW or DDP.
When to use each method
- Flat-rack / open-top: cargo slightly over container size, on regular liner schedules, where speed and frequency matter.
- Breakbulk on MPP vessels: pieces beyond flat-rack capacity, or full project consignments shipped together.
- Heavy-lift charter: single very heavy units, or whole industrial plants, where dedicated cranes and stowage are essential.
Plan early, ship with confidence
Project cargo rewards early planning: get dimensions, weights and lift points confirmed, commission surveys, and brief your forwarder before you commit to a delivery date. When you are ready, post your project-cargo shipment on GDS and receive competitive quotes from forwarders who specialise in OOG, breakbulk and heavy-lift moves.
