Open top and flat rack containers are the most practical sea freight answer for cargo that will not pass through the doors or under the roof of a standard box. Machinery, generators, transformers, steel structures, boats and large production-line modules are too tall or too wide for closed containers. That is where open top and flat rack containers come in: an open top allows crane loading from above, while a flat rack has no side walls and gives over-width cargo the space it needs. Özd Global uses both types regularly for oversized shipments leaving the Gebze and Kocaeli industrial zone. This article explains how each is built, which cargo suits which type, the limits involved and what to watch for when booking.
What Is an Open Top Container?
An open top container is a standard dry box with the steel roof removed and replaced by removable roof bows and a tarpaulin. The side walls, floor and doors remain in place. Its main advantage is crane loading from above, so pieces too tall or heavy to enter through the doors by forklift are placed with ease.
Typical Uses for Open Top Containers
- Machinery and tanks slightly taller than a standard container
- Glass, marble and granite blocks that require top loading
- Long pipes and profiles loaded through the roof rather than the doors
- Scrap, billets and industrial raw materials
If the cargo rises above the container height, the tarpaulin cannot close and the shipment is classified as out-of-gauge (OOG); the carrier then charges for the slot above as well.
What Is a Flat Rack Container?
A flat rack container consists only of a reinforced floor and two end walls; on some models the end walls fold down. The floor carries far higher point loads than a standard container and is fitted with lashing rings.
Typical Uses for Flat Rack Containers
- Construction equipment, excavators and crane components
- Transformers, boilers and pressure vessels
- Boats, yachts and caravans
- Steel structures, prefabricated modules and moulds
Cargo on a flat rack must be protected with tarpaulin or dedicated packaging; otherwise it is exposed to salt spray and rain for the whole voyage.
Dimensions and Weight Compared
The table below gives approximate figures; expect small variations between manufacturers and carriers.
| Container type | Approx. internal length | Approx. internal width | Approx. internal height | Typical max payload |
|---|---|---|---|---|
| 20' open top | 5.9 m | 2.35 m | 2.35 m | around 28 t |
| 40' open top | 12.0 m | 2.35 m | 2.35 m | 26–28 t |
| 20' flat rack | 5.9 m | 2.40 m | 2.20 m (end wall) | 30–45 t |
| 40' flat rack | 12.0 m | 2.40 m | 2.00 m (end wall) | 40–45 t |
The higher payload of flat rack containers makes them the clear choice for heavy, compact pieces. Open tops are the economical alternative when cargo does not overhang sideways but must be loaded from above.
Which Container for Which Cargo?
Choosing between open top and flat rack containers comes down to a few simple rules:
- Cargo exceeds height only, width is standard: Choose an open top; even if the tarpaulin cannot close, the side walls still offer protection.
- Cargo is both wide and tall: A flat rack is essential.
- Cargo is very heavy but in-gauge: The flat rack floor is safer; timber beams spread the point load.
- Cargo is very long (over 12 metres): Several flat racks can be joined side by side as a platform. This solution falls under project logistics and needs dedicated engineering.
Tip: For out-of-gauge cargo, the dimensions declared to the carrier should include packaging but exclude lashing gear and timber skids. Under-declaring by a few centimetres can result in the container being refused at the terminal.
Booking and Operational Considerations
Equipment Availability
Open top and flat rack containers are far scarcer than standard boxes. In peak periods sourcing can take weeks, so book early. Özd Global works with several carriers across its sea freight operations to reduce equipment risk.
Lashing and Survey
For out-of-gauge cargo, carriers usually require a lashing report from an independent surveyor. Securing with chains, tensioners and timber chocks is calculated against the vessel's roll and acceleration values. No report, no loading.
The Inland Leg
Before the container reaches the vessel, it must travel from factory to port. Overhanging cargo may need special road permits, escort vehicles and time-window restrictions, so the road freight plan should be arranged alongside the ocean booking.
How Freight Is Calculated
For out-of-gauge cargo, freight is based not on the container but on the number of lost slots. Over-height cargo blocks the slot above; over-width cargo blocks the slots beside it. Rates therefore vary widely, and a firm quote needs full dimension, weight and packaging details.
Heavy and Oversized Cargo with Özd Global
From its warehouse and field team in Gebze, Özd Global manages loadings of open top and flat rack containers from factory gate to port terminal under one roof. Dimension checks, lashing plans, survey coordination, road permits and customs declarations sit with the same team, so there are no gaps in responsibility.
Frequently Asked Questions
What is the key difference between open top and flat rack containers?
An open top keeps its side walls and doors with only the roof open; a flat rack has just a floor and end walls. Side-overhanging cargo needs a flat rack; cargo that only needs top loading suits an open top.
How much more does freight cost for out-of-gauge cargo?
The increase depends on how many slots are blocked. Over-height-only cargo sees a limited uplift, whereas cargo exceeding both width and height can cost several times a standard container, depending on carrier and route.
Can cargo on a flat rack be insured?
Yes, although insurers typically require a professional lashing report and adequate packaging. Because the cargo is exposed, premiums may be somewhat higher than for a standard container.
Open top and flat rack containers, when planned properly, allow oversized and heavy cargo to travel safely by sea. Share your cargo's dimensions and weight with Özd Global for a firm quote through our contact page or by calling +90 551 462 41 34.
