How should you choose the material for a shipping crate (wood, plywood, OSB) for sea, air and road transport?

Solid wood, waterproof plywood or OSB – each of these materials has different mechanical properties, a different weight, different moisture resistance and a different price. Choosing the material for a shipping crate is not a matter of preference – it is a technical decision that should be based on the type of transport, the characteristics of the cargo and the conditions along the route. A solid wood crate, which works perfectly at sea, will be heavy and expensive to transport by air. Conversely, a lightweight OSB crate may not survive a voyage lasting several weeks in a container exposed to moisture and salt. In this article, we show how we select the crate material for a specific transport route – and why this choice has real financial consequences for the shipper.

Three materials, three characteristics – timber, plywood, OSB

Wood – a classic with exceptional durability

Solid wood is the most versatile construction material for building transport crates. It offers the highest mechanical strength against bending, shearing and point loads. It is ideal for use as a material for bases, stanchions, runners and load-bearing components of the crate. It can be joined using machine screws, spiral nails and steel fittings – which provides great design flexibility when constructing crates for non-standard loads.

The disadvantage of solid wood is its relatively high weight (density approx. 450–550 kg/m³) and the need to comply with ISPM 15 requirements for export – the wood must undergo heat treatment (HT) and be marked with an IPPC stamp. At Danpol, we use heat treatment with parameters that are more stringent than the minimum requirements of the ISPM 15 standard, resulting in timber with lower residual moisture content and better mechanical properties. Each crate bears an IPPC stamp that is permanently and clearly printed.

Waterproof plywood – lightweight and moisture-resistant

Waterproof plywood (WBP grade – Weather and Boil Proof) is a material that is significantly lighter than solid wood whilst maintaining good strength. The wall thickness of a plywood crate is usually 9–15 mm (compared to 18–30 mm for solid wood), which translates into significant weight savings. Waterproof plywood is moisture-resistant – it does not swell or delaminate when in contact with water, making it a good choice for the maritime transport of light cargo.

OSB board – a cost-effective alternative

OSB (Oriented Strand Board) is a material made from compressed wood strands, layered to ensure strength. It is cheaper than plywood and timber, making it an attractive option for large-scale packaging production. 

A limitation of OSB is its lower resistance to moisture compared to waterproof plywood. Standard OSB (OSB/2) is not suitable for environments with high humidity – it swells and loses its strength. The OSB/3 version (for damp conditions) is better, but still inferior to WBP plywood. Therefore, we mainly use OSB in road and air transport, where exposure to moisture is brief. In maritime transport – only as material for side walls and the cover, never for the base or load-bearing elements.

Sea transport – what materials and why

Sea transport involves the longest exposure of the crate to damaging factors: relative humidity inside the container of up to 95%, salty air, condensation (so-called ‘container rain’), dynamic loads resulting from the ship’s rolling (up to 0.8 g laterally) and port handling operations. A shipping crate must withstand 2–8 weeks in these conditions without losing its structural integrity.

For sea transport, we recommend shipping crates made from solid wood as the primary material – for the base, side panels, runners and load-bearing components. Solid wood offers the highest resistance to dynamic loads and can be reinforced with steel fittings. We manufacture the walls and lid from solid wood (solid-walled crates) or from plywood. OSB board is permitted in sea transport only as a secondary material – never for load-bearing components.

Wall thicknesses for sea transport: solid wood 22–30 mm, plywood 12–18 mm. Solid wood base with a minimum stanchion cross-section of 75 x 75 mm for loads up to 1 tonne, and 100 x 100 mm for loads over 1 tonne. Steel fittings (corner fittings, screw closures, reinforcements) are standard for loads over 500 kg.

The timber used to construct shipping crates must be ISPM 15-certified and bear the IPPC stamp. At Danpol, we use heat treatment with parameters exceeding the minimum requirements of the standard – this results in timber with a lower residual moisture content, which reduces the amount of moisture released inside the packaging. This is important for corrosion-sensitive cargoes, vacuum-packed in VCI film.

Air transport – weight is the priority

In air freight, every kilogram of packaging directly affects the freight cost. Air freight rates range from €3 to €8 per kilogram (based on actual or volumetric weight, whichever is higher). Therefore, optimising the weight of the crate is the number one priority. At the same time, air transport takes a short time (1–5 days), and the climatic conditions in the cargo hold are controlled – humidity and salt content do not pose a significant risk.

For air transport, we recommend crates made from waterproof plywood or OSB/3 board for the sides and lid. The base is made from solid wood – but with minimal cross-sections sufficient to allow safe handling by a forklift on the cargo ramp. We opt for aluminium or plastic reinforcements instead of heavy-duty steel fittings. The whole structure is 40–60% lighter than its sea-going counterpart with the same internal dimensions.

Important note: if the base of an airway container is made of solid wood, it is still subject to ISPM 15 when exported outside the EU. A container made entirely of plywood and OSB does not require an IPPC certificate. This is a further argument in favour of using engineered materials in air transport.

Road transport – the greatest flexibility of choice

Road transport offers the greatest flexibility in terms of material selection. Transport times are short (ranging from a few hours to several days), climatic conditions are controlled (depending on the season and route, but without extreme maritime humidity), and dynamic loads are lower than in sea transport. ISPM 15 does not apply to intra-EU routes, which further expands the range of available materials.

In road transport, we use all three materials – the choice depends on the weight of the load and the budget. Solid wood is used for bases and load-bearing components (particularly for loads over 500 kg). Plywood for the walls of solid-walled crates to protect against dust and mechanical damage. OSB for economy crates for less sensitive loads. For lighter loads, pallets with extensions are often sufficient instead of solid crates – they are cheaper and quicker to produce.

For road transport on international routes outside the EU (e.g. Poland–Turkey, Poland–the UK post-Brexit), ISPM 15 applies – solid wood must bear the IPPC stamp. It is worth bearing this in mind when planning export routes that extend beyond the European Union.

Comparison of materials – decision table

Parameter	Solid wood	Waterproof plywood	OSB board
Mechanical strength	The highest	OK	Average
Moisture resistance	Average (depending on processing)	High (WBP class)	Low (OSB/2) / medium (OSB/3)
Weight	The highest	Low	Low
Price of the material	Lowest	High	Average
Is ISPM 15 required?	Yes	No	No
Typical wall thickness	18–30 mm	9–18 mm	12–18 mm
Sea transport	Recommended	Good (walls)	Only as an aid
Air transport	Just the basics	Recommended	Good
Road transport	Versatile	Good	Good

Mixed solutions – combining materials in a single crate

In practice, we rarely build crates from a single material. We usually opt for mixed solutions that combine the advantages of different materials. Typical combinations include:

Solid wood base + plywood walls. The most common configuration for sea transport. Solid wood ensures the base is sturdy and can be reinforced with fittings, whilst the waterproof plywood on the walls provides lightness and resistance to moisture. Note: if the base is made of solid wood, the entire crate is subject to ISPM 15.

Solid wood base + OSB walls. An economical option for road transport and short sea voyages. OSB on the walls reduces the cost of the crate by 15–25% compared to plywood. We do not recommend this configuration for long sea voyages (over 3 weeks) due to OSB’s limited resistance to moisture.

Solid wood + steel fittings. Configuration for heavy loads (over 2 tonnes) and maritime/offshore transport. Steel corner fittings, screw-on fastenings and flat bar reinforcements increase the structure’s strength without significantly increasing its weight. We use various types of fittings selected to suit the specific nature of the load and the customer’s requirements.

Bodywork materials and corrosion protection – what you need to know

The choice of crate material affects the conditions inside the packaging. Solid wood releases moisture – even heat-treated wood contains a certain amount of residual moisture, which can condense on the metal surfaces of the cargo inside a closed crate. Therefore, the export packaging of metal cargo in wooden crates always requires additional anti-corrosion protection – regardless of the crate material.

We use two separate protective systems. ZERUST/EXCOR VCI (Volatile Corrosion Inhibitors) film – an American film wrapped directly around the load, which releases volatile corrosion inhibitors that form an invisible protective layer on metal surfaces. Separately, we use aluminium barrier film (ALU) – an outer layer that hermetically seals the interior of the packaging off from moisture and atmospheric gases. Combined with vacuum packaging, these two systems provide protection for up to 24 months.

With crates made of plywood and OSB, the issue of residual moisture in the wood is less of a concern (processed materials have a lower moisture content), but for sea transport, anti-corrosion protection is mandatory regardless of the crate material – salty air and condensation inside the container affect the cargo from the outside, not just from the side of the wood.

How does the material used for the crate affect the total cost of transport?

The cost of the crate material is only part of the equation. The total cost depends on three factors: the price of the packaging itself (material + labour), the impact of the packaging’s weight on freight costs, and any ISPM 15 certification costs.

Solid wood is the cheapest material per kilogram, but it results in the heaviest crate – which is of marginal importance in sea freight (where charges are based on cubic metres), but critical in air freight (where charges are based on weight). Plywood is more expensive as a material, but results in a lighter crate – with air freight, the weight savings often outweigh the higher material cost. OSB is a cost compromise – cheaper than plywood, lighter than solid wood.

ISPM 15 certification incurs an additional cost of around 10–20% of the value of a pallet or crate. A crate made entirely from recycled materials (plywood, OSB) eliminates this cost and the associated logistical risks. This is a factor worth considering for large packaging runs.

Crate material and container dimensions

The material from which the crate is made affects how it is secured inside the container. Heavier solid wood crates require more robust container stowage – stowage timber with a larger cross-section, a greater number of Cordstrap straps and more careful placement of anti-slip mats. Lightweight crates made of plywood or OSB are more prone to shifting within the container – lower weight means less friction with the floor – and also require careful securing, albeit using different methods.

Regardless of the material used for the crate, the dunnage used inside the container (wedges, struts, blocking logs) must be ISPM 15 certified and bear the IPPC stamp – even if the crate itself is made entirely of plywood. Our staff, trained by SGS Poland and Cordstrap, carry out lashing in accordance with IMO/ILO (SOLAS) guidelines.

The most common mistakes when selecting box material

Standard plywood instead of waterproof plywood. Interior-grade plywood delaminates in conditions of high humidity. For sea transport, only WBP (Weather and Boil Proof) plywood should be used.

Solid wood for an air freight crate, without weight optimisation. A solid wood box with 25 mm thick walls and steel fittings – shipped by air. Every unnecessary kilogram costs €3–8 in freight charges. A box made of 9 mm plywood would be 40–60% lighter and perfectly adequate for short-haul air transport.

No ISPM 15 certification on the wooden components of a mixed crate. The crate has plywood sides (which do not require ISPM 15 certification) but a solid wood base (which does require ISPM 15 certification). The exporter fails to obtain certification for the base – the goods are detained at the border. Every solid wood component in the crate is subject to the standard.

Using a single type of material where a mix would be optimal. Building the entire crate from solid wood when the walls could be made of plywood unnecessarily increases weight and cost. Conversely, using plywood throughout when the load is heavy and requires a reinforced base made of solid wood. The choice of material should vary within a single crate.

Frequently Asked Questions (FAQ)

Does a crate made entirely of plywood not require an ISPM 15 certificate?

Exactly. Plywood, OSB and other processed materials are not subject to the ISPM 15 standard, as their production process eliminates harmful organisms. However, if a crate contains even a single solid wood component (e.g. a stringer, a skid or a wedge), the entire crate is subject to certification. This also applies to wooden dunnage wedges inside the container.

Which material is the cheapest for a crate?

Solid wood has the lowest price per kilogram of material, but results in the heaviest crate. Plywood is more expensive as a material, but lighter – which reduces air freight costs. OSB offers a balance between price and weight. The total cost (material + freight) depends on the mode of transport – which is why we calculate it individually for each order.

Is OSB suitable for use in shipping crates?

OSB in the OSB/3 grade (for damp conditions) can be used as a material for the walls and lid of a shipping crate – but not for the base or load-bearing components. We always recommend WBP waterproof plywood as a safer alternative. 

How much does a plywood box weigh compared to a wooden one?

A crate with 12 mm plywood sides is 30–50% lighter than a 22 mm solid wood equivalent with the same internal dimensions. When switching to 9 mm plywood (for air transport), the difference is as much as 40–60%. The actual weight saving depends on the dimensions of the crate.

Could you choose the material for the box for me?

Yes – this is a standard part of our service. Based on information about the cargo (weight, dimensions, fragility), the mode of transport and the destination market, we recommend the optimal material configuration. We often suggest hybrid solutions (combining timber, plywood and fittings) that best balance strength, weight and cost.

Summary

The choice of material for a shipping crate is a decision that should be based on an analysis of three factors: the mode of transport (sea, air, road), the characteristics of the cargo (weight, sensitivity to weather conditions, value) and the requirements of the destination market (ISPM 15, recipient’s requirements). Solid wood is the dominant choice for sea transport and heavy loads. Waterproof plywood is used in air transport and as the material for the walls of sea crates. OSB is used in road transport and as a cost-effective alternative for short journeys.

At Danpol, we select materials individually for each order – combining timber, plywood, OSB and steel fittings in the optimal configuration for the specific load and route. Over 30 years of experience, a timber drying facility with treatment exceeding ISPM 15 requirements, and an ISO 9001:2015 quality management system – explore Danpol’s full range of services.

Do you need a crate tailored to your transport route? Get in touch with us– we’ll select the right material and design the packaging.