What Is Dunnage Lumber and How Is It Used in Ocean Freight?

If you work in logistics, freight, or manufacturing, you've probably heard the term dunnage — but what exactly is it, and why is it so critical in ocean freight?

What Is Dunnage Lumber?

Dunnage lumber refers to low-grade wood boards and timbers used to protect, brace, block, and separate cargo during transport. It's not a finished product — it's a functional material designed to keep your freight safe and stable from origin to destination.

Common dunnage sizes include 2x4, 4x4, and custom dimensions depending on the load requirements.

How Is Dunnage Used in Ocean Freight?

In ocean freight and container shipping, dunnage lumber serves several critical functions:

• Load separation — Placed between layers of cargo to prevent shifting and crushing during transit.
• Blocking and bracing — Wedged against cargo to prevent movement inside the container, especially during rough seas.
• Elevation — Raises cargo off the container floor to allow forklift access and protect against moisture.
• Weight distribution — Spreads load evenly across the container floor to prevent structural damage.
• Void filling — Fills empty spaces in the container to minimize cargo movement.

Why ISPM-15 Certification Is Required

When dunnage lumber is used in international ocean freight, it must comply with ISPM-15 — the international standard for heat-treated wood packaging materials. Non-certified dunnage can be rejected at customs, quarantined, or destroyed, causing costly delays to your shipment.

Heat-treated (HT) dunnage is stamped with the ISPM-15 mark, confirming it has been treated to eliminate insects and pathogens that could spread invasive species across borders.

Choosing the Right Dunnage for Your Shipment

The right dunnage depends on your cargo type, container size, and load weight. Key considerations include:

• Species — Pine, hemlock, and ash are common choices. Hardwoods like ash offer greater strength for heavy loads.
• Dimensions — 2x4 is standard for light separation; 4x4 is used for heavier blocking applications.
• Length — Cut to fit your container width or cargo dimensions.
• Quantity — Bulk orders ensure you always have supply on hand for ongoing shipments.

Bulk ISPM-15 Dunnage Supply in Ontario

At Cedarwood Ontario, we supply heat-treated, ISPM-15 certified dunnage lumber in pine, hemlock, and ash — available in bulk quantities of 2,000 pieces or more. We serve manufacturers, freight companies, and exporters across Ontario.

Need a custom size or species? We also offer made-to-order dunnage for specialized freight requirements.

Call us at 519-576-5788 or browse our dunnage lumber collection to get started.