7th Dec 2022 -

When constructing a wooden building, choosing a structural wood capable of supporting all weight is vital. C16 timber is graded to ensure that it offers a solid level of strength, making it perfect for structural applications within buildings, such as frames and joists. In this guide from Building Materials Nationwide, we’ll explain the essentials of C16 timber: what it is, how it’s graded, and where it can be used. We’ll also show a brief comparison to C24 timber, the other popular construction timber used in the UK.

What is C16 Timber?

C16 timber is classified as any kiln-dried softwood timber that has passed the criteria certifying it to the C16 grade. C stands for coniferous, or softwood. This rating shows the strength of the timber and means that it can be safely used in construction projects. When looking to buy carcassing timber within the UK or Europe you will traditionally have the choice between C16 and C24 grades. C16 is the most widely used timber within the UK. All C16 is kiln-dried to ensure a moisture level of less than 20%.

Need High-Quality C16 Timber?


    • Ideal for general construction, fencing, garden and leisure timber applications
    • Pressure-treated
    Price from: £4.18 £5.02

    • Ideal for general construction, fencing, garden and leisure timber applications
    • Pressure-treated
    Price from: £6.51 £7.81

    • Ideal for general construction, fencing, garden and leisure timber applications
    • Pressure-treated
    Price from: £7.83 £9.40

View All C16

Here are the stress grades for C16 timber as laid out by BS (British Standards) 5268-2:

Strength ClassMeasurementPassing Amount
Bending Parallel to GrainN/mm25.3
Tension Parallel to GrainN/mm23.2
Compression Parallel to GrainN/mm26.8
Compression Perpendicular to GrainN/mm21.7
Shear Parallel to GrainN/mm20.67
Mean Modulus of ElasticityN/mm28800
Minimum Modulus of ElasticityN/mm25800
Characteristic Densitykg/m3310
Average Densitykg/m3370

These tests determine the strength and consistency of any length of timber, ensuring they are suitable for use within building projects. When using C16 timber it’s important to remember that the C16 rating is on the whole beam, so if you cut the beam across its cross sections or reduce the thickness you’ll need to have it re-graded before you can consider it C16 wood. All C16-graded wood will be stamped.

What Wood Is C16 Timber Made From?

C16 timber can be made from a variety of different types of softwood; as long as they pass the grading process they will be suitable for usage. This could be woods such as pine, cedar, or fir.

What Sizes Does C16 Timber Come in?

C16 timber can come in a huge variety of sizes and lengths. Building Materials Nationwide stocks C16 timber in the following sizes:

  • 47mm x 50mm
  • 47mm x 75mm
  • 47mm x 100mm
  • 47mm x 125mm
  • 47mm x 150mm
  • 47mm x 175mm
  • 47mm x 200mm
  • 47mm x 225mm
  • 75mm x 150mm
  • 75mm x 225mm

Is C16 Timber Treated?

C16 timber will always be kiln-dried to reduce moisture, so it isn’t available as green timber. But when it comes to treatment, both treated and untreated C16 timber is available for purchase. Treated timber can be used in outdoor environments or ones that are exposed to the elements, resisting erosion from rain and a variety of insects that could otherwise burrow into wood. Certain types of timber are treated with a fire retardant, which can also give clear benefits within a building. Even if you are using C16 timber internally there are benefits to getting a treated wood. For example, it increases the durability of wood, extending the lifespan of your building, so even internal components like wall joists could benefit from being made from treated timber.

What is C16 Timber Used For?

C16 timber is used for structural work in many types of wood-framed buildings. This can mean frames for a house or other building, or it can mean joists within a roof, wall, or floor. It can also be used for decking or other external features, providing it is treated. C16 timber can also be used to construct a stud wall.

Can C16 Timber be Used Externally?

Providing it is treated, C16 timber can be used externally for everything from the outer structure of a building to decking. Treated timber comes with water resistance as well as insect resistance, helping your wooden structures to avoid erosion or damage. Exterior wood will need to be maintained regularly to ensure its long-term performance.

timber stud

What is the Difference Between C16 and C24 Timber?

C24 is a higher grade of construction softwood, providing better strength and a more consistent quality throughout. C16 beams may have some defects, such as faults or cosmetic marks. However, for most purposes within a building, they will be perfectly strong to use. The cases where it may be prudent to opt for C24 timber instead would be for key load-bearing components within larger or heavier buildings, and for areas where the wood will be visible, as C24 is likely to have a slightly more attractive appearance. In a lot of cases, C16 will be completely acceptable and will come with significant savings when costing an entire building project. For elements like floor joists, where the wood will not be visible, using C16 will likely be a wiser choice.

Our Range of C16 Timber For Sale

Building Materials Nationwide aims to offer everything needed for a construction project in one easy place, with delivery options across the country. We stock a huge range of timber products, including quality kiln-dried C16 treated timber. This can be used throughout a building project, including for external applications. We aim to be the one-stop shop for builders, contractors, and anyone looking to complete their own projects.

For customers working within the industry, we offer trade accounts, getting you access to a dedicated account manager who’ll be there to offer product advice and help source whatever products you might need. Sign up for a trade account through our website today, gaining access to a string of benefits. If you have any questions before signing up, send them via the below contact form.

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