What Is an Open Top Container?

Q: What is the maximum cargo height for an open top container?

Cargo loaded in an open top container can protrude above the side rails, subject to carrier approval. Typical above-rail clearance permits 30-50 cm of protrusion. The absolute limit is set by the transport route: road bridges, rail tunnels, and vessel stowage positions all impose practical caps. You must confirm maximum cargo height with the carrier before booking.

Q: How is an open top container different from a flat rack?

An open top has rigid side walls like a standard container but a removable tarpaulin roof, making it suitable for tall cargo that fits within standard width and needs side-wall protection. A flat rack has only a floor and end walls (fixed or collapsible) with no sides. Open tops provide lateral containment and basic weather cover; flat racks handle cargo that is over-width.

An open top container is a standard ISO container with one modification: the rigid roof is replaced by a removable tarpaulin cover and the door-end top rail can swing away. This lets a crane lower cargo in from above. The walls and floor are the same Corten steel as a dry container. The roof is a reinforced PVC tarpaulin secured by ropes through eyelets along the top rails, with a bow-shaped arch to shed water. The roof opening is narrower than the internal width, typically 2.22 to 2.23 m for a 20-foot unit, because the structural top rails eat into the opening.

When Do You Use an Open Top?

The basic problem it solves: the door opening on a standard 20-foot container is about 2.34 m wide by 2.28 m high. A 40-foot high-cube door is about 2.59 m high at best. If your cargo is taller than that, a generator, a reactor column, a large fabricated steel section, you cannot fork it through the back doors. You lower it in from above with a crane, a mobile harbour crane, or a gantry.

That is the open top's job. It gives you top access while keeping side walls for cargo restraint and some weather protection from the tarpaulin. The side walls also give you lashing points that a flat rack does not offer in the same way.

Open Top vs. Flat Rack: The Practical Decision

Ask three questions about the cargo:

Is it wider than 2.35 m (internal) / 2.44 m (external)? If yes, you need a flat rack, an open top cannot take it.
Is it taller than about 2.28 m (door height) but within standard width? This is open top territory. The cargo can protrude above the top rails, usually 30 to 50 cm is acceptable with carrier approval.
Does it need side-wall weather protection? Open top wins. The tarpaulin keeps rain off. A flat rack gives no overhead cover at all.

The gotcha: many shippers book an open top expecting the tarpaulin to keep cargo dry. It will not. The cover keeps rain out, but condensation forms inside during temperature swings. Cargo can arrive wet despite the cover. Pack accordingly.

Specifications

Open tops come in 20-foot and 40-foot sizes. The actual dimensions vary slightly by manufacturer and shipping line. Based on published carrier and manufacturer specifications:

20-foot open top: Internal length ~5.90 m, width ~2.35 m, floor-to-top-rail height ~2.35 m. Door opening ~2.34 m wide x ~2.28 m high. Roof aperture ~5.67 m x ~2.23 m. Max gross weight 30,480 kg (standard), tare ~2,260-2,740 kg, max payload ~27,740-28,220 kg. CIMC offers a heavy-duty 35,000 kg MGW variant.
40-foot open top: Internal length ~12.03 m, width ~2.35 m, floor-to-top-rail height ~2.35 m. Door opening ~2.34 m x ~2.28 m. Roof aperture ~11.80 m x ~2.23 m. Max gross weight 30,480 kg, tare ~3,700-4,400 kg, max payload ~26,080-26,780 kg.
40-foot open top high cube: Floor-to-top-rail height ~2.65 m. Roof aperture narrower at ~2.19 m. Max payload ~26,570 kg.

The tare weight is slightly heavier than a same-size dry container because of the reinforced top rails and the tarpaulin assembly.

Common Cargo Types

Scrap metal is the single largest commodity moved in open tops, it is loaded by crane or grab from above. Generators, compactors, large industrial valves, prefabricated steel sections, logs and timber, and oversized construction materials are all typical. Anything tall, heavy, and awkward to get through rear doors.

Operational Constraint

The tarpaulin cannot support weight. Nothing can stack on top of an open top. On a container vessel, open tops go in the uppermost tier on deck or the top cell of a hold stack. This limits where they can be stowed and sometimes means an open top booking costs more than a flat rack, not because of the equipment cost, but because it consumes a premium stack position.

Frequently Asked Questions

What is the maximum cargo height for an open top container?

Cargo can protrude above the side rails, subject to carrier approval. Typical above-rail clearance allows 30-50 cm of protrusion. The absolute cap depends on the route, road bridges, rail tunnels, and vessel stowage positions all limit total height. Confirm maximum height with the carrier before booking.

How is an open top container different from a flat rack?

An open top has rigid side walls and a removable tarpaulin roof. A flat rack has only a floor and end walls (fixed or collapsible) with no sides and no roof. Open tops suit tall cargo that stays within standard width and benefits from side-wall protection and some weather cover. Flat racks suit cargo that is over-width, or needs side access for loading. The open top tarpaulin provides basic overhead weather protection but is not watertight.

Related Terms

Flat Rack, A container with only a floor and end walls, no sides or roof. Used for cargo that is oversize in width and height.
OOG, Out of Gauge; cargo exceeding standard container dimensions, requiring open tops, flat racks, or platforms.
Breakbulk, Non-containerized cargo shipped as individual pieces.