Are Shipping Containers Fireproof? How to Build a Fire-Resistant Container
Shipping containers may look fireproof because of their steel construction, but the reality is more complicated.
In this build, Channing explains why an unmodified shipping container can fail during a fire and walks through a fire-resistant wall and floor system designed for a 20-foot shipping container being converted into a fire pump house.
The goal is to create a container modification that can better satisfy National Building Code requirements while improving fire resistance throughout the structure.
Why Shipping Containers Are Not Fireproof
One of the biggest misconceptions is that a steel shipping container cannot burn.
While the steel shell itself is extremely durable, other components can become a problem during a fire. The underside of many shipping container floors has a bitumen-based coating that can ignite under extreme heat.
Once that coating catches fire, the plywood floor can also burn and create significant smoke inside the container.
That means the floor is one of the first areas that needs to be addressed when designing a fire-resistant shipping container.
Building a Fire-Resistant Container Floor
For this project, two inches of spray foam insulation were installed underneath the shipping container.
An intumescent coating can then be applied over the spray foam to create an additional fire barrier.
Inside the container, the original plywood floor was retained and covered with a cementitious layer. A 3/16-inch steel checker plate floor was then installed over top and seam-welded to create a sealed steel surface.
Using a moisture-resistant cement board instead of drywall at the floor also helps reduce the risk of moisture damage.
Steel Stud Framing and Composite Steel Stud Brackets
The walls are framed with steel studs rather than wood.
Container Modification World Steel Stud Brackets are used to establish the wall and ceiling planes and provide mounting points for the steel stud tracks.
For this fire-resistant build, Composite Steel Stud Brackets are especially important. Unlike aluminum brackets, the composite version does not create the same direct thermal bridge through the wall assembly.
The composite brackets are made from glass-filled nylon resin and are designed to provide a strong connection while reducing heat transfer.
Across the ceiling, 2 1/2-inch steel studs are installed and later locked into the spray foam insulation.
Installing a Fire-Rated Man Door
A fire-rated wall system also requires the correct door.
This project uses a 90-minute fire-rated door with panic hardware and a self-closing device.
The door is installed before the container is spray-foamed so the insulation and wall assembly can be completed cleanly around the frame.
Creating the Interior Wall Assembly
The interior uses three separate layers to improve fire resistance.
The first layer is 5/8-inch Type X drywall, with the seams sealed using fire-rated caulking.
A layer of fire-rated plywood is then installed over the drywall.
The final finish is Class A flame-spread PVC wall paneling. This provides a clean, moisture-resistant interior that is especially useful because the finished container will house large water tanks and a fire pump.
Building a Safer Shipping Container
This project demonstrates that shipping containers are not automatically fireproof simply because they are made from steel.
However, with the right combination of steel stud framing, Composite Steel Stud Brackets, spray foam insulation, intumescent coatings, fire-rated drywall, fire-rated plywood, PVC wall panels, and a properly rated door, a shipping container can be built into a much more fire-resistant structure.
The next step for the container modification industry is full-system fire testing. Individual materials may already have established ratings, but testing complete shipping container wall assemblies would provide clearer data for engineers, architects, and builders designing code-compliant container buildings.
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