OOG Cargo Shipping Guide: Open Top, Flat Rack, and Platform Containers

Not all cargo fits neatly inside a standard shipping container. Out of Gauge (OOG) cargo—shipments that exceed the dimensions of a standard 20-foot or 40-foot container—requires specialized equipment, expert planning, and careful execution. From wind turbine blades and construction machinery to industrial tanks and oversized steel structures, OOG shipping is a critical capability for project logistics and heavy industry exports from Global.

This guide explains the fundamentals of OOG cargo shipping, the specialized container types used (open top, flat rack, and platform), dimensional limits, lashing and securing techniques, permit requirements, and how OOG shipping costs are calculated.

What Is OOG Cargo?

OOG (Out of Gauge) cargo refers to any shipment whose dimensions exceed the internal dimensions of a standard general purpose (GP) container. A standard 40-foot container has internal dimensions of approximately 12.03m x 2.35m x 2.39m (L x W x H). If your cargo is taller than 2.39m, wider than 2.35m, or longer than 12.03m, it cannot fit inside a standard container and must be shipped using specialized equipment.

OOG cargo is further categorized based on how it overflows the container dimensions:

• OOG Height: Cargo exceeds the container's internal height (over-height)
• OOG Width: Cargo exceeds the container's internal width (over-width)
• OOG Length: Cargo exceeds the container's internal length (over-length)
• OOG Multiple: Cargo exceeds dimensions in two or more directions

Additionally, some cargo fits within container dimensions but is too heavy to load through the container doors. This is sometimes called "door-loading cargo" and may also require open top or flat rack equipment for top-loading or side-loading.

Open Top Containers

Open top containers are designed for cargo that is too tall to fit through standard container doors or that requires top-loading via crane. They have a removable tarpaulin roof instead of a solid steel top, allowing cargo to be loaded from above.

Specifications

Specification	20'OT	40'OT
Internal Length	5.898m	12.032m
Internal Width	2.346m	2.345m
Internal Height (under tarp)	2.346m	2.346m
Door Opening Width	2.330m	2.330m
Door Opening Height	2.262m	2.262m
Max Payload	~28 tons	~30 tons

Typical Open Top Cargo

• Tall machinery and equipment that exceeds 2.3m height
• Pre-fabricated building materials and structural steel
• Large pipes, tubes, and cylindrical tanks
• Heavy machinery parts (turbines, generators, transformers)
• Cargo that must be loaded by crane from above

Open top containers are sealed with a weather-resistant PVC tarpaulin that is secured with ropes or tensioning devices. The tarp protects cargo from rain and sea spray but does not provide the same level of weather protection as a solid steel roof. For cargo sensitive to moisture, additional internal wrapping or desiccant protection is recommended.

Flat Rack Containers

Flat rack containers consist of a steel floor with foldable or fixed end walls and no side walls or roof. They are the most versatile OOG equipment type, capable of handling cargo that is over-width, over-height, over-length, or any combination. Flat racks are available in 20-foot and 40-foot sizes, with collapsible end walls that allow multiple empty flat racks to be stacked for efficient repositioning.

Specifications

Specification	20'FR	40'FR / 40'HC FR
Floor Length	5.946m	12.080m
Floor Width	2.318m	2.318m
End Wall Height	2.233m	2.233m / 2.540m (HC)
Max Payload	~31 tons	~40-55 tons
Lashing Points	Multiple along floor and end walls	Multiple along floor and end walls

Typical Flat Rack Cargo

• Over-width cargo: construction vehicles, agricultural equipment, industrial machinery
• Over-height cargo: tall tanks, reactors, boilers, silos
• Over-length cargo: pipes, beams, wind turbine components (up to 12m+ on 40' flat rack)
• Heavy machinery: excavators, cranes, bulldozers, drilling equipment
• Project cargo that requires side-loading or crane loading

For extremely heavy or oversized cargo, 40-foot flat racks with 40+ ton payload capacity are available. Some specialized flat racks are rated for up to 55 tons, accommodating heavy industrial equipment such as large transformers and pressure vessels.

Platform Containers (40'PL)

Platform containers (also called bolster containers or flatbeds) are flat steel decks with no end walls, side walls, or roof. They are used for extremely large or heavy cargo that exceeds even flat rack capabilities. Platform containers are primarily available in 40-foot length and can handle payloads up to 40-50 tons.

Platform containers are less common and more expensive than flat racks, but they offer maximum flexibility for:

• Cargo exceeding 12m in length
• Cargo requiring the full width without end wall interference
• Exceptionally heavy items that need a flat, unobstructed deck
• Multiple items that need to be arranged in a non-standard configuration

Size and Weight Limits for OOG Cargo

While OOG containers can accommodate cargo exceeding standard dimensions, there are practical and regulatory limits. Each carrier publishes its own OOG acceptance guidelines, which are generally based on the following framework:

Height Limits

• Open Top: Over-height up to approximately 4.0m total (cargo height above the container floor). Beyond this, special stowage and lashing engineering is required.
• Flat Rack: Over-height cargo can extend several meters above the deck, but total height (including the flat rack) must allow for vessel cell guides and bridge clearance. Maximum practical height is typically 4.5m above the deck.

Width Limits

• Cargo wider than 4.0m on a flat rack may require special arrangements and is subject to carrier approval.
• Width exceeding 5.0m is extremely difficult to containerize and may require RoRo shipping or break-bulk shipping instead.

Length Limits

• Cargo can overhang a 40-foot flat rack by approximately 1-2 meters at each end, depending on carrier policy.
• For cargo exceeding 15 meters, consider break-bulk shipping or specialized project cargo solutions.

Weight Limits

• 20' flat rack: up to ~31 tons
• 40' flat rack: up to ~40 tons (standard) or ~55 tons (heavy-duty)
• 40' platform: up to ~50 tons
• Weight limits are also constrained by origin and destination port lifting capacity, road weight restrictions, and vessel structural limits.

Lashing and Securing OOG Cargo

Proper lashing and securing of OOG cargo is arguably the most critical aspect of OOG shipping. Ocean vessels experience significant motion—rolling (side-to-side), pitching (front-to-back), and heaving (vertical)—that exerts tremendous forces on cargo. Inadequate securing can lead to cargo shifting, equipment damage, vessel instability, and even loss of containers overboard.

Lashing Principles

OOG cargo securing follows the IMO Code of Safe Practice for Cargo Stowage and Securing (CSS Code). Key principles include:

• Direct lashing: Chains, wire ropes, or synthetic webbing attached directly from the cargo to lashing points on the flat rack or platform.
• Friction lashing: Synthetic belts tightened over the cargo to increase friction between the cargo and the container floor, preventing sliding.
• Blocking and bracing: Timber blocks, steel chocks, or custom-fabricated cradles that prevent cargo movement in any direction.
• Combination approach: Most OOG shipments use a combination of direct lashing, friction lashing, and blocking for maximum security.

Lashing Materials

• Steel chains and turnbuckles: High-strength, reusable, suitable for very heavy cargo
• Wire rope clips and grips: Flexible and strong, commonly used for industrial equipment
• Synthetic webbing (ratchet straps): Lightweight, easy to handle, suitable for medium-weight cargo
• Timber dunnage and chocks: For blocking, bracing, and distributing weight
• Custom steel cradles: Welded or bolted frames designed for specific cargo shapes

Professional Lashing Services

OOG lashing should always be performed by certified professionals. In China, major ports have designated lashing companies that are approved by carriers and classification societies. These companies provide:

• Cargo securing plans engineered to CSS Code standards
• Certified lashing materials with test certificates
• Photographic documentation of the lashing arrangement
• A lashing certificate that carriers require before accepting the booking

SHAQ Logistics works with certified lashing teams at all major Chinese ports and supervises the entire securing process to ensure compliance and safety. Learn more about our special container shipping services.

Permit Applications and Route Surveys

OOG cargo often requires special permits for inland transportation, port handling, and in some cases, ocean routing. The permit process varies by country and cargo dimensions.

Inland Transportation Permits (China)

Transporting OOG cargo by road in China requires permits from local transportation authorities. Requirements vary by province but typically include:

• Oversized load permit application with cargo dimensions and weight
• Route survey to verify bridge clearances, road width, and weight restrictions
• Escort vehicle requirements for cargo exceeding certain dimensions
• Night-time or off-peak transport restrictions in urban areas
• Special permits for cargo exceeding 4.3m height (standard bridge clearance in many areas)

Port Handling Approvals

OOG cargo requires special handling arrangements at both origin and destination ports:

• Advance notification to port operations with cargo dimensions and stowage plan
• Special equipment allocation (reach stackers, mobile cranes, multi-lift spreaders)
• Designated stowage position on the vessel (often on deck or in specific cell guides)
• Reefer or DG stowage compatibility checks if cargo has special requirements

How OOG Shipping Costs Are Calculated

OOG shipping is significantly more expensive than standard container shipping due to specialized equipment, handling complexity, and space utilization inefficiency. Understanding the cost structure helps you budget accurately.

Base Ocean Freight

OOG ocean freight is quoted as a premium over the standard container rate. The premium depends on the degree of over-gauge:

• Open Top (within gauge height): +20% to +40% over standard 40'GP rate
• Flat Rack (over-height only): +30% to +50% over standard rate
• Flat Rack (over-height and over-width): +50% to +100% over standard rate
• Platform (extreme OOG): Quoted on a case-by-case basis, often 2-3x standard rate

Additional Surcharges

• OOG Surcharge: Charged by the carrier based on the cargo's over-gauge dimensions and stowage complexity
• Lost Slot Charge: Compensation for adjacent container slots that cannot be used due to OOG cargo overhang
• Special Equipment Fee: For flat rack or platform rental if not included in the base rate
• Lashing and Securing Fee: Professional lashing service cost
• Cargo Securing Material Cost: Chains, wire rope, timber, and custom cradles
• Port Handling Surcharge: Additional crane and labor costs for OOG handling
• Survey and Permit Fees: Route surveys, engineering plans, and government permits

Cost Estimation Example

For a 40-foot flat rack shipment of over-height machinery from Shenzhen to Rotterdam, a typical cost breakdown might include:

• Base ocean freight (40'FR rate): $3,500
• OOG surcharge (over-height): $1,200
• Lost slot charge (2 slots): $1,000
• Flat rack rental: $300
• Professional lashing service: $500
• Lashing materials: $400
• Port handling surcharge: $400
• Total estimated ocean-side cost: ~$7,300

This is in addition to origin trucking, customs clearance, documentation, destination port charges, and destination delivery—all of which also carry OOG premiums.

Choosing Between OOG, RoRo, and Break-Bulk

For oversized or heavy cargo, OOG container shipping is one of several options. Depending on your cargo characteristics, RoRo shipping or break-bulk shipping may be more suitable:

• OOG Containers: Best for cargo that fits on a flat rack or open top (up to ~12m length, ~40 tons) and benefits from container handling efficiency
• RoRo: Best for self-propelled or towable vehicles and machinery (cars, trucks, construction equipment)
• Break-Bulk: Best for extremely large or heavy items that cannot be containerized (vessel components, industrial modules over 50 tons or 15m)

Conclusion

OOG cargo shipping requires specialized equipment, engineering expertise, and meticulous planning. Whether you need an open top container for over-height machinery, a flat rack for over-width equipment, or a platform for extreme project cargo, understanding the capabilities and limitations of each option is essential for successful shipping.

By following proper lashing and securing standards, obtaining necessary permits, and working with an experienced OOG logistics provider, you can ship oversized cargo from Global with confidence. SHAQ Logistics has extensive experience handling OOG shipments of all sizes from Chinese ports, with certified lashing teams, carrier relationships, and project logistics expertise. Learn more about our special container services and project logistics capabilities.

Have OOG cargo to ship from Global? Contact SHAQ Logistics for a free consultation and detailed OOG freight quote.