Bridge Products

Plywood vs Hardwood Bridge Decking

Engineered plywood bridge decking offers several advantages over traditional sawn hardwood planks. The cross-laminated veneer structure distributes load evenly in both longitudinal and lateral directions, reducing the localised stress concentrations that cause hardwood planks to split and loosen fasteners under heavy vehicle traffic. Plywood panels are lighter and larger than individual hardwood planks, which means fewer crane lifts, fewer fastener points and significantly faster installation – a critical factor for councils managing road closures on regional routes.

Standards and Design Compliance

Timber bridge design in Australia is governed by AS 5100.9:2017, which was introduced as part of the 2017 Bridge Code revision to formally recognise engineered timber alongside steel and concrete. Structural plywood for bridge applications must be manufactured to AS/NZS 2269 with a minimum stress grade of F14 for traffic-bearing decks. All timber bridge components in ground or water contact require preservative treatment to Hazard Class H4 under AS/NZS 1604. Big River’s bridge decking is manufactured to these standards at our Grafton plywood mill.

Compatibility with Existing Substructures

Plywood bridge decking is not limited to timber substructures. Engineered panels can be installed on timber, steel and concrete supporting structures, making them suitable for both rehabilitation of existing bridges and new construction. Cantilevered panels can also extend deck widths beyond the girder line to accommodate pedestrian walkways or cycle paths – a common requirement in council bridge upgrade programs.

Treatment and Wearing Surface

All bridge decking must be H4 treated for durability in exposed and in-ground conditions. Big River’s plywood uses A-Bond (phenolic) adhesive for permanent waterproof performance. A durable wearing surface must be applied over the plywood deck to protect against abrasion and UV degradation – the wearing surface specification directly affects achievable service life. Contact Big River’s technical team for advice on treatment specifications and wearing surface options for your project.

Sustainable Sourcing

Availability of structural-grade old-growth hardwood has declined significantly, driving both cost increases and supply uncertainty for traditional bridge timbers. Big River’s bridge products use PEFC-certified (PEFC/21-31-174) plantation pine – a renewable, sustainably sourced alternative manufactured in regional NSW. This aligns with the increasing emphasis on sustainability in public infrastructure procurement under AS 5100.9 and Austroads guidelines.