As a material often sourced for internal walls, roof and wall sheathing, Oriented Strand Boards (OSB) are one of the most popular solutions for structural building projects. Favoured for their cost-effectiveness and strength, they are used as an alternative to traditional plywood. Manufactured in a process that concentrates on cross-directional layering of timber strands, the boards combine the use of sustainable timber and resins. OSB not only delivers on structural integrity through excellent strength and durability, but also offers reassurances as a wood-based, responsibly sourced material. For example, EGGER’S OSB Flammex contains 92% material from renewable resources and is fully recyclable at the end of its life.
OSB boards are a reliable, engineered solution avoiding the challenges presented by the likes of knots or internal voids – known to create weak spots in natural timber. Ease of processing is another clear advantage of OSB. It is easy to cut, handle and fix on site, without chipping, and with consistent quality and uniform board dimensions makes it easy to ensure a reliable installation.
OSB’s popularity may be linked to its multiple installation possibilities, but with these numerous applications across large projects and ever-evolving building regulations comes the need for OSB’s market offering to evolve.
Specifying and sourcing the correct materials is of the utmost importance when working on ‘higher risk’ buildings or other areas where enhanced fire performance is required. It’s essential that the walls, ceilings and floors within protected escape routes (such as corridors and staircases) are designed and constructed to limit the spread of fire and smoke. While requirements vary across the UK, Approved Document B gives guidance in England on meeting fire safety requirements. In these applications, protected escape routes and compartmentation need to be considered as part of the wider safety strategy, with requirements varying by building type, use and location.
Fire-resistant plasterboard can be a valid option for internal applications where fire ratings are required. But this choice will not provide the practical benefits that OSB offers – mainly, the structural racking performance, impact resistance and better fixing capabilities (such as screw and nail holding). Where enhanced reaction-to-fire performance is required by the project’s specification, sheathing boards need to achieve a Euroclass B-s1, d0 classification. This means the boards will help limit fire spread, smoke production and flaming droplets.
For these applications, OSB boards with an enhanced reaction-to-fire classification can meet the criteria required by specifiers, providing both structural and fire-safety performance. In the event of a fire, the flame-retardant intumescent coating on the surface of the board reacts and forms a barrier, helping to limit flame spread across the surface and slow down the burn-through of panel.
EGGER OSB FLAMMEX
EGGER’s OSB Flammex is an evolution of its standard OSB 3 board. Achieving a Euroclass B-s1, d0 reaction-to-fire classification, the board’s flame-retardant intumescent coating reduces fire spread, smoke generation and the production of burning droplets or articles. The flameretardant coating is applied and tested by EGGER, meaning OSB Flammex is supplied as a complete tested and declared product, with its OSB/3 structural performance and Euroclass b-s1, d0 reaction-to-fire classification covered by the relevant CE marking and Declaration of Performance. This is in comparison to other standard plywood boards that are fire-treated after production, resulting in the declared structural performance certification potentially needing to be re-checked.
OSB Flammex is also in the Structural Timber Association’s ‘Fire During Construction’ tested products list for timber frame sheathing applications. Part of wider construction-phase fire safety guidance for structural timber, this relates to managing fire risk during construction, particularly where buildings are close to neighbouring properties or there is a risk of external ignition.
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