Flat rack vs. open top: which container for OOG cargo?
Out-of-gauge (OOG) cargo does not fit through the door or exceeds the size of a standard container. Open tops and flat racks are the two main solutions – each for a different problem.
Key facts
- Open top: removable roof – for tall cargo and loading by crane from above
- Flat rack: no side walls or roof – for wide, tall and heavy cargo
- 40' flat rack: up to about 40 t payload
- Overheight / overwidth costs extra because neighbouring slots on the vessel are lost
Dimensions and payload
| Equipment | Floor L × W (cm) | Height (cm) | Max. payload (kg) |
|---|---|---|---|
| 20' OT | 589 × 235 | 234 | 28,000 |
| 40' OT | 1,203 × 235 | 234 | 26,500 |
| 40' HC OT | 1,203 × 235 | 265 | 28,000 |
| 20' FR | 562 × 220 | 223 | 31,000 |
| 40' FR | 1,165 × 222 | 196 | 40,000 |
When to use an open top
- Cargo is taller than the door (2.28 m) or must be lifted in by crane.
- Cargo fits within the width of the container (2.35 m inside).
- Slight overheight is possible – the tarpaulin is then fitted around the cargo.
- Cheaper and more protected than a flat rack.
When to use a flat rack
- Cargo is wider than the container (overwidth) – e.g. machinery, vehicles, steel structures.
- Cargo is very heavy – a 40' flat rack carries up to about 40 t.
- Very long cargo: a platform (flat rack without end walls) can be used.
- Lashing with chains or belts to the D-rings is essential – plan the lashing points early.
Overheight and overwidth
Overheight is measured above the normal container height, overwidth per side beyond the container width. The more OOG, the more slots the carrier loses on deck – which drives the freight rate. Carriers need drawings, weight and centre of gravity for approval.
Several OOG pieces on one flat rack
Smaller OOG pieces can share one flat rack if the floor length, the total weight and the concentrated load allow it. plan4cargo checks this automatically in the OOG tab and places the heaviest piece in the middle to keep the centre of gravity centred.
Values are typical figures for standard equipment. Actual dimensions and limits vary by carrier, container and country – always check with your carrier.
Frequently asked questions
What is the difference between open top and flat rack?
An open top is a normal container with a removable roof (side walls stay). A flat rack has only a floor and end walls – no side walls and no roof – so it can carry wider cargo.
How heavy can cargo on a 40ft flat rack be?
Typically up to about 40 t, but the load must be spread – concentrated loads on a short length are limited much more.
Can I load cargo that is too tall for a 40ft High Cube?
Yes, with an open top or flat rack as overheight cargo. The carrier must approve it in advance.