9x3 Timber Treated C24
(6 Products)75mm x 225mm treated timber is an elite structural section designed for high-performance engineering projects that require maximum span capability and lateral stiffness. Pressure-treated to provide long-term protection against biological decay, these 9x3 lengths are a primary choice for deep-profile floor joists and high-specification roofing systems.
Understanding 9x3 Treated Timber
75mm x 225mm sawn treated timber, frequently identified by its nominal 9x3 inch trade size, is a foundational component for large-scale structural framing where standard 2-inch widths are insufficient. These sections are kiln-dried to improve dimensional stability and are strength-graded to C24 standards. This ensures a high-density material with minimal defects, providing the mechanical resistance necessary for safety-critical structural elements that must support significant permanent and imposed loads.
To ensure performance in demanding environments, the timber undergoes a high-pressure preservative treatment process. This forces biocides deep into the cellular structure, creating a robust barrier against fungal rot and wood-boring insects. This treatment makes the 9x3 profile exceptionally durable for first-fix structural work, where the framework may be exposed to the elements before the building envelope is fully sealed.
The timber is regularised to a finished size of approximately 72mm x 220mm. This precision machining ensures a uniform profile across all lengths, which is vital for achieving level planes in flooring and roofing. The eased edges improve site safety and ergonomics, while the substantial 75mm width provides a generous bearing surface for fixings and structural connections.
Material Range
- Individual 75mm x 225mm Lengths: Heavy-duty structural pressure-treated lengths available in 3.6m, 4.8m, and 6m sizes to meet rigorous engineering specifications.
- Bulk 9x3 Timber Packs: Trade-scale 35-length packs designed for high-volume efficiency, providing a consistent supply for large-scale structural installations across all stocked lengths.
Performance Benefits
- Enhanced Load Bearing: The 75mm width offers superior compression strength and a larger bearing surface, reducing the risk of crushing at support points.
- Biological Resistance: Pressure-treated with advanced fungicides and insecticides to prevent rot and decay in both internal and external applications.
- C24 Structural Integrity: Offers higher tensile strength and stiffness than standard domestic timber, facilitating wider spans and heavier load capacities.
- Dimensional Stability: Kiln-dried to strictly control moisture content, ensuring the timber remains straight and stable after installation.
Typical Applications
- Long-Span Floor Joists: Supporting internal flooring in large residential rooms and commercial units requiring maximum rigidity.
- Primary Roof Rafters: Forming the main structural framework for heavy pitched or flat roof designs.
- Mezzanine Floor Construction: Creating high-strength secondary floor levels in industrial or retail environments.
- Timber Frame Studwork: Acting as heavy-duty structural studs or sole plates in load-bearing wall panels.
External Support Frameworks: Providing a robust, rot-resistant base for substantial elevated platforms and decking.
Specification & Standards
- BS EN 14081-1: Strength graded structural timber with rectangular cross section.
- BS EN 335: Durability of wood and wood-based products – Use classes.
- BS EN 599-1: Performance of preventive wood preservatives as determined by biological tests.
Related Materials and Construction Uses
These 75mm x 225mm sections are the preferred choice for contractors requiring premium structural wood with superior density and strength. In many high-spec builds, these deep profiles are used in conjunction with other specialised joist timber products to create a high-performance system that minimises bounce and deflection over long spans.
To maintain the protective barrier of the pressure treatment, any on-site cuts, notches, or drill holes must be retreated with an end-grain preservative. These heavy-duty sections should be installed using appropriately sized galvanised hangers and high-tensile fixings to ensure the long-term structural safety of the assembly.
Frequently Asked 9x3 Questions
What Is A First-Fix Construction?
In construction, the term 'first-fix' essentially entails the construction work required to take a structure from its foundation to the stage of applying internal surfaces - typically the plastering of internal walls.
Can You Burn Pressure-Treated 9x3 Timber?
Under no circumstances should pressure-treated wood be set alight. The fumes released when pressure-treated wood burns can be harmful to health and the ash itself is toxic.
We advise against using pressure-treated wood for making any form of food preparation surface due to this toxicity.
Is It Possible To Paint 9x3 Timber C24?
Pressure-treated wood can be painted or stained, but to get a finish that lasts and looks premium, you'll first need to evaluate the moisture content of the timber.
Once you are sure the timber is dry, you can then move on to using a suitable primer and paint finish. We recommend using a latex primer with compatible exterior latex paint—water-based paint. Oil-based paints are not recommended.
Am I Able To Cut 9x3 Timber To My Preferred Size?
Yes, it is possible to cut treated timber, provided that you have all the appropriate power tools, eye protection, and a respirator to hand before cracking on. Donning the correct PPE is essential as the cutting process releases tiny airborne particles of wood, possibly impregnated with the chemicals used in pressure-treating.
Treated wood also cuts a little more like wet wood so some extra care should be afforded to ensure the blade doesn’t slip while cutting.
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