Stringer

A stringer is the longitudinal timber, plastic, or metal beam that runs beneath the deck boards of a stringer-type pallet

A stringer is the longitudinal timber, plastic, or metal beam that runs beneath the deck boards of a stringer-type pallet and provides primary load-bearing capacity. In pallet construction the stringer supports vertical loads from the pallet deck and transmits those loads to the ground or to forklift and pallet-jack tines during handling. Stringers determine many functional attributes of a pallet, including static and dynamic load capacity, allowable entry directions for handling equipment, suitability for racking, and options for repair and modification.

Common materials for stringers include softwood (e.g., pine), hardwood (for higher strength or reuse applications), engineered wood (finger-jointed or laminated), plastic, and steel. Wooden stringers are the most widespread in general warehousing because of cost and ease of repair. Plastic stringers offer chemical and moisture resistance and are typical in hygienic or export-sensitive supply chains. Metal stringers show up in heavy-duty pallets designed for very high loads or repeated automated handling.

There are several practical stringer configurations:

• Unnotched stringers: Solid beams running the full width of the pallet. They typically permit only two-way entry by forklifts unless special deckboard spacing is used.

• Notched stringers: Cut-outs or notches provide clearance for forklift or pallet-jack tines, enabling four-way entry. Notches reduce local cross-section and therefore influence rated capacity and fatigue life.

• Block vs stringer pallets: In block pallets, multiple block supports replace continuous stringers to permit four-way entry without notching. Stringer pallets use longer longitudinal members and are often cheaper and easier to repair.

How stringers are used

Stringers are selected, manufactured, and arranged to meet the handling, storage, and transport needs of the product and facility. Key use aspects include:

• Load distribution: Properly sized and positioned stringers spread loads across deck boards and into handling tines or the ground. For heavy or concentrated loads, wider and thicker stringers or additional center stringers may be required.

• Forklift and pallet-jack entry: Notched stringers or four-way stringer designs allow forklifts to enter from all sides; unnotched designs restrict entry and can limit material flow patterns in a warehouse.

• Racking compatibility: Pallets intended for selective pallet racking must meet dimensional and structural criteria. Some racking systems require reinforced stringers or block-style pallets for secure racking support.

• Repair and lifecycle management: Wooden stringers are the primary field-repair element of many pallets. Damaged stringers can be replaced or reinforced, extending pallet life and reducing total cost of ownership.

When stringers are chosen or required

Stringer-type pallets are selected for a range of situations based on cost, handling patterns, and load characteristics. Typical scenarios include:

• General warehousing and distribution where cost-effectiveness and easy repair are priorities.

• Applications with predictable two-way or four-way handling flows where notched stringers can be specified to match equipment constraints.

• Export shipments where wooden stringers must meet phytosanitary standards (e.g., ISPM 15 heat treatment and stamping) to prevent pest transfer.

• Industries where pallets are frequently repaired in-house; wooden stringers are straightforward to replace compared with block elements or full plastic pallets.

Design and specification considerations

When specifying stringers, logistics professionals should consider material, cross-section, number and placement of stringers, and whether notches are required. Dimensions and material grade affect static capacity (when the pallet remains stationary), dynamic capacity (when handled by lift equipment), and racking capacity (when supported at edges in a rack). Manufacturers typically provide load ratings for common configurations; however, actual performance depends on condition, moisture content, and how the load is applied.

Inspection, maintenance, and safety

Routine inspection of stringers is essential for safe handling. Common checks include looking for splits, rot, loose or missing fasteners, crushed corners at notches, and deterioration from chemical exposure. Repaired stringers should restore structural integrity using appropriate fasteners, adhesives, or replacement members. Do not use makeshift repairs that compromise capacity or create sharp edges. For food, pharmaceutical, or clean-room environments, plastic or metal stringers may be preferred to avoid splinters and contamination.

Best practices

• Specify stringer type (notched vs unnotched) based on the facility's handling patterns and equipment entry needs.

• Match stringer material and size to expected load profiles and environmental conditions (moisture, chemicals, temperature).

• Implement a pallet inspection and repair program to identify and replace damaged stringers before failure occurs during handling or racking.

• Ensure export wood stringers comply with phytosanitary treatment and marking requirements to avoid border delays.

Common mistakes

• Using pallets with cracked or undersized stringers for heavy or concentrated loads, which can cause sudden failure and product damage.

• Not accounting for the strength reduction caused by notches when switching from unnotched to notched designs.

• Improper in-field repairs that use insufficient fasteners or create stress concentrations, reducing fatigue life.
• Choosing wooden stringers for highly humid or corrosive environments without appropriate treatment or protective coating.

Alternatives and related components

Alternatives to stringer pallets include block pallets, which use discrete block supports enabling inherent four-way entry, and plastic or metal pallets that integrate support members into molded or fabricated designs. Skids (single-deck without bottom stringers) and custom engineered pallets may be used where footprint or load conditions differ. When pallet use involves automated systems, consider pallets with consistent stringer geometry and tight dimensional tolerances to avoid misalignment in conveyors or automated guided vehicles.

In practice, a 48"x40" stringer pallet with three stringers (one center and two outer) remains a common configuration in North America for general distribution: it balances cost, repairability, and load capacity for many fast-moving consumer goods applications. In contrast, high-value or hygienic supply chains often select plastic stringer pallets or block pallets with sealed surfaces.

Overall, the stringer is a small but critical element of pallet design that affects the pallet's load performance, handling compatibility, repairability, and lifecycle cost. Thoughtful selection, routine inspection, and correct maintenance of stringers help reduce product damage, improve safety, and optimize material handling efficiency across warehousing and transportation operations.