Flat Rack vs Open Top Container: Key Differences

Flat rack containers have no side walls or roof, making them ideal for oversized, over-width, or extremely heavy cargo. Open-top containers have enclosed side walls with a removable tarpaulin roof, making them the right choice for tall cargo that fits within standard width. The deciding factor is usually cargo width vs height.

If you have cargo that can’t be shipped inside a standard container, your best options are either a flat rack container or an open-top container.

Both are specialized shipping containers designed to ship cargo that doesn’t fit the standard box format. Among different container types, these two are commonly used for oversized cargo or irregular shipments. But shippers often get confused as to which of these two is the right option for them. Choosing the wrong type adds cost, complicates handling, and can create compliance issues in international shipping.

In this article, we’ll look at the difference between a flat rack vs open top container, including their steel structure, design, and the cargo they can handle. By the end, you’ll get a complete understanding of which one is right for you.

What Is an Open Top Container?

An open-top container is also a specialized shipping container that doesn’t have a solid steel roof. Instead, it offers a removable tarpaulin or hard-top lid, designed for loading over-height or bulky cargo from the top via crane. They are available in 20ft open top and 40ft open top sizes and are used for transporting oversized machinery, steel, and industrial materials. 

Key features of open-top containers:

• Fully enclosed side walls: The container has solid side walls, end walls, and a door set so your cargo is protected on all four sides.
• Removable tarpaulin roof: Instead of a solid steel roof, it comes with a removable tarpaulin roof that provides weather protection while allowing top loading.
• Consistent container width: The internal container dimensions of open top containers match those of standard containers, so you can estimate the loading capacity and storage space easily.
• Lashing rings: Features lashing rings on the floor and walls for securing cargo inside.
• Overhang allowance: It’s ideal for tall cargo that can’t fit inside a standard container. You can just remove the tarpaulin cover to accommodate it. 

Read more about open-top containers here. 

Flat Rack vs Open Top Container

What are the Key Differences Between Flat Rack and Open Top Containers?

Flat rack containers are open on the sides and top, making them ideal for oversized or heavy cargo that needs flexible loading from multiple directions. Open top containers, on the other hand, have solid side walls and use a removable tarpaulin roof, offering better protection while still allowing cargo to be loaded from above.

Structure & Design

In any standard container, the side walls, floor, and roof work together to create a rigid, solid box that protects your cargo and the container itself from elements. This is how most container types are structurally designed for durability and transport safety. 

In special containers like open-top or flat-rack, this is not available. So here’s how the two maintain their structural integrity: 

• Open top: As we mentioned, this is essentially a standard container with a missing roof. Because the roof (which usually provides a lot of stability) is gone, the side walls are reinforced to prevent them from bowing outward. For efficient loading, the rear header, which is the bar above the doors, is designed to swing out or be removed entirely. This allows a crane to drop cargo in without hitting the top of the door frame.
• Flat rack: Since there are no side walls or roof, the entire structural load is carried by the base. Because of this, the floor of a flat rack is significantly thicker and more heavily reinforced with steel beams than an open top. The end walls are incredibly strong and prevent the cargo from sliding forward or backward during transit.

In short, an open top relies on its reinforced side walls for strength, while a flat rack relies on the heavy-duty base frame.

Loading Methods

In a flat rack container, cargo can be loaded from anywhere (top, side, or end). While in an open-top, it has to be loaded from above. 

Open top loading methods: 

• Top-loading (crane): This is the most common method. Since there is no roof, a crane can lower heavy or awkward items (like large glass sheets or heavy scrap) directly into the container from above.
• End loading through doors: Just like standard containers, you can load the cargo through the container door if it fits, and this method doesn’t require crane equipment. 

Flat rack loading methods: 

• Top loading: The cargo is lifted by crane and set down onto the platform surface. This is common for loading large pipes or boilers.
  

• Side loading: The cargo is slid or rolled onto the flat rack from either long side using forklifts, heavy equipment, or specialized rollers.
  

• End loading: Cargo can also be loaded from either short end when the end walls are in the collapsible position. This option isn’t available for fixed-end flat-rack containers. 

Cargo Types

Here are some of the specific cargo types that are shipped in these containers.

For open-top containers:

• Any tall cargo that exceeds standard container height limits but fits within standard container width.
• Glass panels and similar fragile materials that need to be placed carefully in the container and need enclosed side protection.
• Heavy machinery like wind turbine blades and similar elongated components.
• Bulk minerals or scrap metal items like coal, ores, or heavy copper scrap can be loaded simply by dumping them in from an overhead hopper.
• Construction materials that need to be craned in from above.
• Irregular cargo like tree saplings, where top access is required, but side protection is equally important.

For the following cargo, flat rack containers make more sense: 

• Construction equipment such as bulldozers, excavators, and large tractors. These are often wider than a standard container and far too heavy for a regular wooden floor.
  

• Yachts and oversized boats, because a boat’s hull is usually much wider than a container. Or jet engines or fuselage sections, as they require specific lashing points.
  

• Project cargo, industrial turbines or transformers that can weigh 40+ tons. Such heavy materials require the reinforced ‘I-beams’ found in a flat rack’s floor to prevent the container from snapping in half.
• Over-width industrial boilers or massive concrete piping sections that must be loaded from the side because they are too long and wide to maneuver through rear doors.

Here’s a golden rule we advise container buyers when they’re selecting between the two. 

If you can’t fit it through the “front door” because of height, go open top.

If you can’t fit it because of width or extreme weight, go flat rack.

But let’s understand where it makes sense to use a flat rack vs. an open-top container in more detail. 

When to Use a Flat Rack Container

Use flat-rack containers when your cargo is too wide, too heavy, or too structurally irregular to fit in any container with walls. 

It’s also useful if you’re shipping extremely heavy industrial machinery, as the platform is built specifically for heavy loads.

Specific scenarios where flat rack containers are the correct container type:

• Oversized cargo: If your cargo is wider than 2.35 meters (approx. 7 ft 8 in), it physically can’t fit inside an open top or a standard container.
• Extremely heavy machinery: If the cargo weighs more than 30,000kg (for a 40ft unit), opt for a flat rack unit as its reinforced platform can easily handle the load.
• Complex cargo loading requirements: Cargo that needs to be rigged, crane-lifted, and set down with precise positioning requires unrestricted side access that a flat rack provides.
• Large vehicles and rolling stock: To transport cargo that is too large or heavy for roll-on/roll-off loading and too wide for enclosed containers, flat rack containers are a natural fit.
  

It also makes economic sense to use a flat rack container if you’re only using it for one-way transport. The collapsible ends mean you can easily stack 4-5 units of flat racks, which is about the same space as a standard container on a vessel. So you save a significant amount on your return shipping costs.

When to Use an Open-Top Container?

Open top containers are the right choice when cargo is too tall for a standard container but still fits within the standard container width.

Here are some specific use cases where it’s the right choice:

• Tall cargo within standard width: Any machinery, equipment, or materials taller than 2.38m (standard container interior height) but no wider than standard container dimensions are ideal open top candidates.
• For fragile materials: Open tops are the right choice for materials like glass panels that need top loading but also need enclosed walls for protection.
• For difficult rear loading: Sometimes cargo isn’t over-height, but it’s so heavy that a forklift can’t lift it high enough to clear the top bar of a standard container door. As we mentioned, most open tops have a removable rear header so you can swing it out of the way, slide your cargo in, and then lock the header back into place.
• Bulk materials loaded from above: Materials like scrap metal, glass sheets, or large bags of minerals that need to be loaded by conveyor or crane bucket into the container. 

To help you better understand which is the right choice for you, let’s take a look at the container dimensions and capacity that each of these containers can hold. 

Container Dimensions & Capacity Comparison Between Open Top and Flat Rack Containers

For both flat racks and open tops, the most common sizes are the 20ft and 40ft versions. Here’s a comparison between the two to help you make the right choice. 

Pros and Cons of Open Top and Flat Rack Containers 

When choosing between these two, it usually comes down to a trade-off between protection (open top) and flexibility (flat rack).

Here is the breakdown of the advantages and drawbacks for each:

Now let’s take a look at the pros and cons of flat racks. 

Pricing Differences Between Flat Racks and Open Top Containers 

Both flat racks and open top containers have a higher purchase price and freight rates than standard containers. This is due to their limited supply in the container market, the fact that they require special slots on a vessel, and require special handling equipment. 

Here’s a realistic estimate of the costs. 

Here’s a detailed explanation of why the prices of these special containers are higher than standard ones. 

• The “lost slot” premium: If your cargo sticks out of an open top, the vessel loses one slot above it, so you have to pay for that. Similarly, on a flat rack, if your cargo occupies space above, to the left, and to the right, you have to pay for that space too.
• Specialized handling & equipment: Most ports and depots have automated cranes that can lift standard containers. But handling specialized cargo requires manual crane operations, specialized spreaders, or heavy-lift gear at the port, all of which trigger significantly higher terminal handling charges (THC).
• Lashing and Labor: Open tops use the side walls for stability, keeping lashing costs lower. Flat racks require professional-grade securing, like heavy-duty chains, timber bracing, and even welding steel stoppers to the base, which adds a hefty bill for specialized labor and materials. 

These are just a few of the factors that affect the pricing. Always get in touch with your logistics partner to get a detailed overview of what it would cost to ship materials in these special shipping containers. 

How to Choose the Right Shipping Container? 

Here’s a list of practical questions that will help you choose the right container. 

1. Does cargo exceed standard container width (2.35m)?
   Flat rack is the only viable container option.
2. Does cargo exceed standard container height (2.38m) but fit within standard width?
   An open-top container is likely the right choice.
3. Does the cargo require side protection during transit?
   The open top provides enclosed walls, while the flat rack does not.
4. Is the cargo extremely heavy (above 28 tonnes)?
   Flat rack handles higher weight limits.
5. Does the cargo need to be loaded from the side?
   Only flat rack containers allow side loading.
6. Is the cargo fragile or sensitive to weather exposure?
   Open top’s enclosed walls and tarpaulin provide better protection than a flat rack tarpaulin.
7. Will empty shipping containers need to be returned cost-effectively?
   Flat rack with collapsible end walls reduces return freight cost.
8. Is the cargo irregular in shape?
   Flat rack provides better access for complex handling.

If you need more guidance, get in touch with our team. Our experts will guide you towards the right choice based on your specific requirements and will also provide you with the best buying or renting options. 

Request your custom quote today.