Choosing the Right Timber
Ensuring the timber you use will stand the test of time
Lightweight and strong with a plentiful supply, timber is the first choice structural material today as it has been for hundred’s of years. To ensure that timber stands the test of time, it’s vital that you use timber that’s of the right strength and preserved to the right level.
Selecting the right timber for the job
New Zealand Pinus radiata is a versatile, light-coloured softwood renowned for its excellent working properties, easy and rapid drying, and ability to be treated for durability. Available in a wide range of lumber grades, selecting the appropriate grade is essential to meet the specific demands of any building project, ensuring both suitability and performance.
Factors to consider
Timber Sizing
Timber produced by New Zealand sawmills is available in a range of sizes to accommodate various construction needs.
When designing in timber it’s important to have an understanding of the common sizes available.
Timber Grades
Timber is typically classified into three main grades: Appearance Grade, Structural Grade and Industrial Grade.
Choosing the appropriate timber grade ensures that your project meets both its structural and visual needs effectively.
Timber Preservatives
Effective preservation treatments have been developed to ensure Pinus radiata has excellent performance across a broad range of applications where there is exposure to weather and other elements such as salt water. It’s vital you choose the right level of preservation for your use.
Timber Sizing
Timber produced by New Zealand sawmills is available in a comprehensive range of sizes to accommodate various construction needs. Choosing the right size and grade of timber is essential to ensure it meets the specific demands of your project, providing both strength and durability where needed.
These dimensions are provided as rough sawn and dried sizes, ensuring versatility and suitability for a wide array of building applications.
Width
Standard widths include 25mm, 50mm, 75mm, 100mm, 125mm, 150mm, 175mm, 200mm, 225mm, 250mm, 275mm, and 300mm.
Length
Lengths range from 1.8 meters up to 6.0 meters, increasing in 0.3-meter steps.
Thickness
Thicknesses are typically offered in 25mm, 40mm, 50mm, 75mm, and 100mm increments.
Grading Timber
Pinus radiata logs, managed through effective silviculture, are available in a variety of qualities to produce lumber grades for any requirement. Timber is typically classified into three main grades:
Appearance Grade
Clear of knots or with minor blemishes and tight knots, perfect for projects where aesthetics are important.
This grade includes Clear Timber, which is completely free of knots and blemishes, ideal for high-quality joinery, furniture, and mouldings that demand a flawless finish.
Additionally, Cuttings Grades are available for reprocessing, producing shorter clear lengths with excellent machining and gluing properties.
These grades may initially contain large knots and blemishes, which are meticulously removed through cross-cutting and ripping. The resulting clear components are often finger-jointed and edge-glued, ensuring that the final products, such as mouldings and furniture, meet the highest standards of craftsmanship and visual excellence.
Structural Grade
Structural Grade timber is essential for construction projects where strength and stiffness are paramount. This grade is meticulously managed to ensure that the timber can withstand significant loads and environmental stresses.
Key factors influencing structural grades include the size and location of knots as well as the overall density of the timber. By limiting these defects, structural grades meet specified strength requirements, ensuring the integrity and safety of building structures.
Structural grades undergo rigorous quality assurance programmes, such as the Verified Timber programme, which certify that the timber meets its claimed strength and stiffness characteristics in accordance with the New Zealand Building Code.
This stringent management guarantees that structural timber is reliable and performs consistently in demanding construction applications.
Industrial Grade
Industrial Grades timber is specifically designed for practical applications where functionality takes precedence over aesthetic appeal.
Commonly used in packaging products such as pallets, cable drums, and concrete formwork, these grades accommodate a variety of knot sizes suitable for their intended uses.
Additionally, industrial grades are produced for export, including thin-board and other specialised grades tailored to buyer specifications.
Common export grades include:
Australia: AS2858 F5 and F7 structural grades (visual) treated and untreated AS1748 MGP grades (machine stress graded)
United States: Western Wood Products Association random width lumber specifications including mouldings and better, shop and factory grades.
Japan: JAS structural grade specifications (which also include glue laminated and plywood grades)
China and Vietnam: NZS3631 cuttings grades and buyer specified grades
Preserving Timber
Ensuring timber longevity in diverse environments is essential for maintaining the integrity and durability of construction projects. Proper preservation treatments protect wood from weather, moisture, insects, and decay, extending its lifespan and performance across various applications.
Pinus radiata excels in this regard as one of the most treatable species of wood. Its unique cellular structure allows preservatives to penetrate deeply and remain within the timber, enhancing its durability to withstand even the most challenging conditions.
The New Zealand Timber Preservation Council website has a wide range of information available regarding the importance of treating timber, how timber is treated, how to choosing the right timber based on its use and how timber preservation is assessed using the WOODmark® quality assurance programme. Here are some quick links to give you all the information you need.
Why Treat Timber
Not all wood is naturally tough. Pinus radiata, the main timber used in New Zealand and Australia, isn’t naturally resistant to insects and decay.
To make it durable and meet building standards, it may need quality preservative treatment.
The level of treatment depends on the timber’s planned use, ensuring it can withstand various environments and meet different durability requirements. Timber can be treated using a range of different chemicals depending on its end use.
How To Choose The Right Timber
When choosing treated timber for your home or building project, it’s crucial to make sure that the wood has been treated with the correct preservatives.
These preservatives safeguard the timber from decay, insects, and other damaging elements, ensuring it remains durable for many years. In New Zealand, timber treatment is governed by the NZS 3640:2003 and AS/NZS 1604 standards, which outlines the approved preservatives and their specific uses.
The Hazard Class of timber indicates the level of treatment it has received to protect it from various hazards such as decay, moisture, and insect attack.
How to Check that Timber Is Treated
Properly treated timber is vital for durability and safety in construction.
Managed by the New Zealand Timber Preservation Council, the WOODmark® quality assurance programme ensures that treated timber meets high standards, giving users confidence in its quality.
WOODmark® licensed treatment plants follow strict health, safety, and environmental guidelines and are regularly audited to guarantee adherence to these stringent standards.
Timber Design Standards and Guides
There are a range of building and design standards and guides available on our Resources for Industry page.
Certified Excellence in Timber: An Overview of WOODmark® and Verified Timber
Introducing WOODmark®
The WOODmark® programme is an independent, national quality assurance brand for timber treatment managed by the New Zealand Timber Preservation Council. This programme ensures that treated timber products meet stringent standards for durability and safety.
The WOODmark® name and symbol signify that a timber product complies with New Zealand's treatment standards, specifically NZS 3640 and AS/NZS 1604. Only licensed treatment plants dedicated to maintaining these high standards are permitted to use the WOODmark® symbol.
By choosing timber products bearing the WOODmark® symbol, you can be confident they have undergone rigorous treatment processes. This guarantees the timber in your projects meets strict preservation criteria, providing peace of mind for builders, architects, and homeowners alike.
Introducing Verified Timber
The Verified Timber programme is an independent national quality assurance brand for structural timber, managed by the New Zealand Timber Industry Federation. This programme ensures that timber products meet stringent standards for strength and stiffness, complying with New Zealand's standards NZS 3603 and NZS 3622.
The Verified Timber name and symbol signify that a timber product has been rigorously tested to meet these standards. Only licensed producers who adhere to the Verified Timber Quality Manual and undergo regular audits are permitted to use the Verified Timber trademark.
By choosing timber products bearing the Verified Timber mark, you can be confident they have undergone stringent quality checks. This guarantees that the timber used in your projects meets strict criteria for structural integrity and reliability, providing peace of mind for builders, architects, and homeowners alike.
Become a NZTIF Member
Join us and help us look after NZ’s timber industry.
NZTIF welcomes new members and works hard to look after the membership community.