Ever felt confused while buying timber for your construction business?

Choosing the right structural timber shouldn’t feel confusing—unfortunately, for many builders and homeowners, it does. The debate between C16 and C24 timber often raises many questions.

Is the stronger option always necessary? 

Is the price difference worth it? And many others 

Misinformation about timber grading can lead to overspending or, worse, structural risks. In this guide, we will break down the real differences, costs, and practical uses so you can confidently choose which one to use for your project. 

But, before identifying which one is best, let’s learn how timber is graded. 

How Is Timber Graded In Australia?

Although timber is a durable building material, but, not all timber types are good enough. 

A good timber is referred to as a piece of wood that can bear the maximum stress downward. 

Why Is Understanding The Timber Grades Important?

Understanding the timber grades is crucial to ensure quality. Engineers use this information to determine the accurate size and spacing by referring to a span table for timber to ensure a timber can withstand the load. The classes of timber are

1- MGP grades — They are categorised based on structural framing strength (e.g., MGP10, MGP12, MGP15, etc.).

2- F-grades — They are graded based on bending strength in MPa (Mega Pascals) (e.g., F5, F7, F11, F14, F34, F17, F22, F27, etc.).

3- GL grades — Used for engineered glued laminated timber beams (e.g., GL8, GL13, GL18).

4- European Strength Classes — Based on bending properties, stiffness, and density (e.g., C16, C24, C35, etc.).

How To Grade Or Identify C16 And C24 Timber

C16 and C24 grade timber can be identified manually and by machine. 

Stamp markings — All softwood timbers are stamped and show C16 or C24.

Visual indicators — The best way to identify timber visually is by appearance. Clean appearance on C24, while C16 looks rough. 

Supplier documentation — Finally, if you are unable to identify by visual inspection and if the stamp is removed, check the supplier documents properly to verify. 

C16 Vs C24 Timber

As a construction business owner, offering premium-quality material is a top priority for your customers. Ply Supply believes great design should never come at the cost of overspending and structural risks. So, let’s break down each timber type in detail. 

Note that according to BS EN 338, C16 and C24 timber types fall under European strength classes. “C” in both C16 and C24 refers to a conifer, and 16 and 24 refer to the strength level. 

Moreover, according to building regulations and compliance, both C16 and C24 should be legally graded to BS EN 14081.

1- What is C16 timber? 

C16 is a kind of softwood timber commonly used for structural softwood grade designs for everyday construction. While the conifer rating of 16 N/mm² for C16 timber indicates the load it can safely support. It is Kiln-dried to reduce moisture and improve stability. C16 may show natural knots or grain variations, which makes it more affordable. 

Despite the imperfections, it provides dependable strength for internal structural uses like stud walls, floor joists, and roof framing. It is an ideal choice for projects that do not require high load-bearing efficiency. 

Pros Of C16 Timber

• C16 is a cheap timber in comparison with other timber types. 
• Strong enough to provide 16 N/mm² structural support.
• Provide stability and eliminate risks of shrinking.
• C16 timber is easy to cut, shape, and install.
• Versatile enough to be used for roof framing and internal structure.

Cons Of C16 Timber

• Lower strength compared to C24, not suitable for big projects.
• Contains more knots and grain deviations.
• Not ideal for high-stress structural applications.
• Usually recommended for internal structure only.
• Appearance is less uniform, so not ideal for aesthetic projects. 

Uses Of C16 Timber 

• Internal stud walls and partition framing in residential construction.
• Floor joists in light domestic building projects.
• Roof rafters and basic roof framing.
• First-fix carpentry (structural framing, finishing work).
• Decking and outdoor landscaping, when properly pressure-treated. 

2- What Is C24 Timber?

C24 timber is a premium structural softwood grade designed for projects where strength truly matters. It is carefully selected and kiln-dried. C24 timber has fewer knots and defects, giving it both superior durability and a cleaner appearance. Because of its strength, it’s commonly used for floor joists, roof rafters, beams, and long-span structures.

Pros Of C24 Timber

• Higher load-bearing strength (24 N/mm²).
• Good for longer beams and heavy-duty applications.
• Fewer knots and defects.
• Kiln-dried for better stability.
• Cleaner appearance for visible structural work.

Cons Of C24 Timber

• Higher cost compared to lower-grade timber.
• over-specified for low-load projects.
• Requires preservative treatment for outdoor use.
• Heavier and harder to handle than softer timbers.
• Limited availability in smaller sizes.

Uses Of C24 Timber

• Floor joists in domestic and commercial buildings
• Roof rafters and trusses.
• Beams and lintels.
• Wall framing for load-bearing walls
• In exposed structural areas for appearance.

C16 Vs C24: Let’s Discover The Key Differences

When To Use C16?

Based on the strength level, C16 timber is ideal for 

• Small residential builds
• Internal wall framing
• Light roofing structures
• Areas with minimal load requirements. 

It works well in short spans, renovation projects, and budget-friendly constructions. However, C16 should not be used for long-span beams, heavy roofing systems, commercial buildings, or high load-bearing structural frameworks.

When To Use C24? 

With the higher strength, C24 timber is suitable for 

• Structural beams
• Floor systems with wider spacing
• Roofing structures carrying heavier loads

It is recommended for longer spans, higher load requirements, and commercial or engineered projects. When pressure-treated, C24 is also ideal for outdoor structures such as decking supports, garden buildings, and landscaping frameworks.

Conifer 16 Or Conifer 24: Which One To Use?

The use of timber totally depends on the design and requirements.

If you are looking for something with a rough appearance, low quality, and budget-friendly wood, C16 will be ideal. 

However, for your high-load-bearing projects, a clean appearance and stronger wood like C24 is recommended. 

Still confused? Let us simplify it. 

Want high-strength timber for building high-end structures? Pick a C24 timber.

Looking for wood for the small and low-load-bearing project? Go for C16 timber.  

Can C16 And C24 Can Be Used Interchangeably?

No, in most cases, they cannot be used interchangeably due to differences in strength and appearance. You can swap them when upgrading to higher C24 timber and need wood for small and low-weight-bearing projects. 

Common Timber Sizes In Australia 

Common timber sizes in Australia for grade C16 and C24 are

Conclusion

The less knowledge of timber grading can lead you to make wrong choices. However, the right timber choice can define the strength, safety, and success of your project. 

C16 offers pocket-friendly cost and enough strength for domestic and small projects. And  C24 is a perfect choice for outdoor and large structures with its high-load-bearing capacity and cleaner finish. 

Whether you need the affordability of C16 or the superior load-bearing power of C24, understanding the difference helps you build smarter—not just cheaper. 

Don’t risk structural performance. 

Contact Ply Supply today, a structural timber supplier, for expert advice and quality building timber.

FAQ 

1- Is C24 grade better than C16?

Yes, in terms of strength and appearance, C24 grade timber is better than C16 grade timber. However, in terms of cost, C16 is cheap as compared to C24 grade timber. Check out the affordable price at PlySupply. 

2- What are the disadvantages of using C16 timber?

 Here are some of the disadvantages of the C16 grade timber. 

• Has less strength compared to C24.
• Good for small and indoor structural projects.
• Contain more knots and grains.
• Recommended for low-stress structures.
• Less uniform and cleaner appearance.

3- What is C16 and C24 timber?

 C16 and C24 grade timber are both types of kiln-dried softwood that originate from conifer wood. Here, “C” stands for conifer, and 16 and 24 refer to minimum strength. C16 is an excellent choice for small and indoor projects, while premium quality C24 timber is the best pick for large and outdoor structural projects.