A Timber Grading Guide In Australia

Whether you're a construction professional, an architect, or a DIY enthusiast, you'll need to understand timber grades when embarking on any project involving wood in Australia. 

This knowledge will ensure that you select the right wood for your specific needs, ultimately impacting the safety, quality, and aesthetics of your finished product.

Timber Grading In Australia 

Timber grading refers to the classification of wood based on its strength, quality, and appearance. It's a system designed to ensure that the right type of timber is used for various construction, architecture, and DIY projects.

There are two main types of timber grading: strength grading and appearance grading. Strength grading pertains to the load-bearing capacity of the timber, making it crucial for structural purposes. 

In contrast, appearance grading focuses on the aesthetic qualities of the wood without considering its strength.

F-Grade Grading System In Australia

The F-Grade system (F5, F7, F11, F17, and so on) is the standard timber grading system  in Australia. 

This system indicates the ability of the timber to withstand force, with higher grades representing stronger timber.  For instance, F5 is used for light framing while F17 is used for heavy construction.

In the timber grading system, stress grades play a crucial role in determining the strength of various types of timber. The "F" grade system is commonly used for visually stress grading most hardwoods and some softwoods. 

For example, a timber grade of F14 means that it can resist a force of 14MPa without excessive deflection. Unseasoned hardwoods typically fall within the F14/F17 range, while kiln-dried hardwoods are usually stronger and fall within the F22/F27 range. On the other hand, pine tends to have lower stress ratings ranging from F5 to F8 due to its inherent properties.

It is important to note that some exceptionally strong species can reach high stress ratings such as F34 when they have been properly kiln-dried and are free of any defects. These exceptional timbers stand out for their superior strength and durability compared to others in lower stress rating categories.

Choosing the correct strength grade is vital for any construction project as it directly relates to the safety and stability of your structure.

What Is MGP Timber?

MGP, which stands for machine graded pine, is a grading system used for certain types of pines such as radiata, slash, and Caribbean varieties. In Australia, Machine Graded Pine (MGP) is a popular choice for many construction projects due to its reliable strength. This type of wood is tested by machines for stiffness and density to ensure it meets specific standards.

Unlike traditional methods based solely on bending strength, MGP takes into consideration additional properties like stiffness, compressive strength, and shear strength by measuring the modulus of elasticity (MOE) of each piece.

The MOE serves as an indicator of how stiff a particular board is - the higher the MOE value, the stiffer the wood will be. 

When assessed by an MGP machine stress grader, each board receives a grade corresponding to its MOE category. 

What does MGP 10 mean?

MGP 10 signifies an MOE of 10,000 megapascals (MPa).

MGP 12 indicates an MOE of 12,700 MPa, andMGP 15 represents an MOE value of 15,200 MPa.

A precise grading system like MGP rating ensures that only high-quality timber with superior structural characteristics are selected for various construction projects.

MGP vs F Grade Timber

MGP material can substitute for F graded material, but F graded material should not be used if MGP material was specified. 

MGP grades have design tables for various properties, while F grades are based on bending strength alone. This could lead to missing important design characteristics, such as compressive and shear strength, if an architect or builder specified an MGP grade for a structural member.

Below are the three main MGP grades and the F grades they can replace.

MGP 10 can replace F5
MGP 12 can be changed for F8
MGP 15 can be interchanged F11

Timber Appearance Grading

On the other hand, appearance grading is all about the look of the timber. The grades (Prime, High Feature, Standard & Better, etc.) are determined by the number and size of knots, colour variations, grain patterns and other aesthetic characteristics.

This type of grading plays a significant role in projects where the visual appeal of the wood is a priority, such as furniture making or home remodelling. The right appearance grade can greatly enhance the aesthetics and value of your project.

Hazard Grading

Hazard levels indicate the severity of biological risk for timber in various applications.

H6 is the highest level, while H1 is the lowest. Each level has specific protective measures against termites, decay, and fungal growth.

H6 Timber - Suitable for marine use as it can be submerged in saltwater.

H5 Timber - Good to be used in full contact with fresh water and the ground.

H4 Timber - Protected against severe decay so can be used outoors in areas with severe wetting.

H3 Timber - Good for outdoor use, on above ground areas.

H2 Timber - Ideal for indoor use

H1 Timber - Ideal for indoor use

Why You Need To Use The Right Timber Grade

Using the right timber grade is not just about aesthetics or strength; it has serious implications for safety, quality, and financial outlay. Incorrect use of timber grades can lead to structural failures or unsatisfactory appearances that may require costly repairs or replacements.

For instance, using a low-strength grade for a load-bearing structure could result in its collapse. Similarly, using a low appearance grade for visible parts of a project could significantly diminish its aesthetic appeal and value.

Final Words

Understanding and choosing the right timber grades is not just about making informed decisions; it's about ensuring safety, quality, and aesthetic appeal in your projects. By increasing your knowledge of timber grades, you can avoid potential mishaps and financial implications.

Whether you're a construction professional, an architect, or a DIY enthusiast, continue to educate yourself about timber grades in Australia. Reputable timber yards like Directline Timbers based on the Sunshine Coast can offer valuable insights and expert advice to help you make the right choices.null