Shipping container floors are typically constructed using marine-grade plywood — a hardwood panel product known for its durability and resistance to moisture. This plywood is specifically selected to protect cargo from water damage during transportation.
The specific materials used for the floor may vary depending on the manufacturer and intended use of the container. However, a common configuration consists of multiple layers:
- Bottom Cross Members: The floor structure begins with steel cross members that run perpendicular to the container's length. These cross members, spaced approximately 12 inches apart, provide the primary structural support for the floor.
- Floor Joists: Wooden floor joists are then attached to the bottom cross members. These joists run parallel to the container's length and offer additional support.
- Marine-grade plywood: Plywood sheets — typically 1⅛ inches (28 mm) thick — are laid over the floor joists with their grain direction running perpendicular to the container's long sides. The sheets are pre-treated to resist moisture, rot, and insect infestation, extending the floor's service life.
- Fasteners: The plywood sheets are secured to the floor structure using nails or screws, often coated or galvanized to prevent rust.
- Treatments and coatings: Many containers receive additional chemical treatments or sealant coatings on the plywood to further guard against moisture ingress, mold, and pest activity. Common treatments include boron-based preservatives and epoxy sealants.
Together, the steel cross members and marine-grade plywood create a strong, durable floor that withstands the rigors of international shipping while keeping cargo stable. Note that marine-grade plywood is moisture-resistant but not fully waterproof, so additional sealing is recommended for wet or humid environments. Some containers also use alternative flooring materials such as bamboo or solid steel plate, which offer different trade-offs in weight, cost, and durability.
