What is C24 Timber?

Grading, strength and why it matters

If you’ve ever looked at structural timber and wondered what C24 means, you’re not alone. It’s one of the most common labels in timber yards — and one of the most misunderstood.

Some people think C24 means the timber is treated. It doesn’t. Others assume C24 is a size or a type of wood. It’s not that either. So here’s a straight answer:

C24 is a strength grading. And if you’re building anything structural — floors, walls, roofs, decking frames — it matters.

What Does C24 Mean?

C24 is a structural strength class used to grade softwood timber. It’s based on how strong, stiff, and durable the timber is under load.

Timber graded to C24 has been visually or machine tested to meet certain performance standards, especially for load-bearing. It’s part of a scale (C16, C18, C24 etc) used across Europe, with C24 being one of the most common grades for UK building work.

C24 vs C16 – What’s the Difference?

In short, C24 is stronger, more stable, and more reliable — especially where heavy loads or long spans are involved.

Is C24 Timber Treated?

No — C24 refers to strength, not treatment. Timber can be:

• C24 and treated (e.g. for outdoor use or decking frames)

• C24 and untreated (e.g. for internal stud walls)

We stock C24-graded sawn timber in a range of lengths and sizes — some treated, some untreated — depending on what the job needs.

Need it treated for external use? Just let us know and we’ll make sure you get the right spec — or we can order in UC3 or UC4 if needed.

When Should You Use C24?

Use C24 timber for anything structural:

• Floor joists

• Roof rafters

• Stud walls

• Decking frames

• Timber frames or outdoor structures

• Anywhere you need strength and reliability

If you’re doing work that needs to meet building regulations, C24 is often the recommended minimum.

What We Stock at Wood Green Timber

We keep a full range of 47mm sawn C24 timber, including:

• 47x100mm (4x2)

• 47x150mm (6x2)

• 47x175mm (7x2)

• 47x200mm (8x2)

• 47x225mm (9x2)

• Longer lengths including 6.0m, 7.2m and 9.0m available in some sizes

We also stock large rough sawn sections and decking-grade treated timber.

If you’re unsure what spec you need, we’ll always talk through your project with you and recommend the right grade and treatment level — no guesswork.

Need Help Choosing Structural Timber?

Drop into our Wood Green or Potters Bar branches and speak to someone who knows their stuff. We’ve been supplying quality structural timber across North London and Hertfordshire since 1981, and we’ll always make sure you get the right wood for the job.

Call us, visit, or order online — proper service, real timber, expert advice.