When working on construction or projects in South Africa, a clear understanding of standard timber sizes is crucial. This knowledge ensures structural integrity, cost-effectiveness, and seamless project execution. In South Africa, timber sizing aligns with specific standards that may differ from those in other countries. Let’s discuss the common timber sizes available locally and their typical applications.
Treated vs. Untreated Timber
Before we move forward, it’s important to understand when timber should be treated and when it’s not necessary.
In South Africa, timber is commonly treated with CCA to improve its durability and resistance to pests and environmental factors. This treatment allows the timber to be used in a wider range of applications. While other treatments exist, CCA is the most widely used, with Tanalith E being a more eco-friendly alternative.
However, not all timber needs to be treated—it depends on its intended use. If the timber won’t be exposed to environmental elements like rain, sunlight, or insects, treatment isn’t necessary.
It’s important to know what CCA-treated timber looks like. With the treatment process, the chemicals are fully penetrated into the timber. Beware of timber that is only coated with a greenish tint, as this is not the correct way of treatment.
Here’s an example:
If you are constructing a timber frame for your deck, it is crucial to use treated timber since it will be outdoors and exposed to moisture, rain, and insects. Using untreated timber in these conditions can lead to rot, decay, and structural weakness over time.
When it comes to treating timber, there are multiple hazard classes it can be treated to, namely: H2, H3, H4, and, not as common, H5. To learn more about their hazard classes, click on the following link: CCA-treated timber Hazard Classes
While H2 is commonly used for construction timber in South Africa, we treat our construction timber to H3 mainly or H4 upon request. We do this to ensure our timber is applicable for most applications. This treatment process is done according to national regulations.
Applications of Standard Timber Sizes
Understanding the typical uses of various timber sizes can aid in selecting the right material for your project:
38 x 38 mm – Battens, Bracing, and Light Framing
This size is commonly used for battens, bracing, and other lightweight framing applications. If used indoors or in areas protected from moisture and pests, untreated timber is sufficient. However, if used in roofing, exterior cladding, or other exposed applications, it should be treated to prevent decay and insect damage.
38 x 76 mm – Wall Studs and Roof Trusses
Typically used for wall studs and roof trusses, this size can be either treated or untreated depending on its application. If used in internal wall framing where it’s protected from moisture, untreated timber is suitable. However, for roof trusses, especially in humid or termite-prone areas, treated timber is recommended for added durability.
38 x 114 mm – Floor Joists and Larger Framing Applications
This size is ideal for floor joists and larger framing work. Since floor joists are often exposed to moisture from the ground or subfloor spaces, treated timber is necessary to prevent rot and insect damage. If used indoors in dry conditions, untreated timber may be sufficient.
50 x 152 mm – Beams and Load-Bearing Structures
This size is used for beams and load-bearing structures where strength is a priority. If the timber will be exposed to outdoor elements, such as for pergolas, decks, or outdoor shelters, it must be treated to withstand moisture, insects, and decay. For indoor load-bearing structures, untreated timber is generally acceptable.
76 x 228 mm – Heavy-Duty Applications (Large Span Beams)
Used in large-span beams and heavy-duty structural applications, this size is crucial in supporting significant loads. If used in exterior or exposed conditions, it must be treated to ensure long-term durability against weathering and pests. For indoor structural use in controlled environments, untreated timber can be used.
Our latest edition: Square timber beams
Square timber beams are durable and ideal for a variety of construction applications. With a clean, uniform shape, they are perfect for pergolas, decking, framework, and interior or exterior cladding. The pressure treatment ensures long-lasting resistance to rot, insects, and harsh weather, making them a reliable choice for both residential and commercial projects. For more information, please click on the following link: Square Timber Beams
Comparing South African Timber Sizes to International Timber Sizes
While South Africa has its own set of standard timber sizes, it’s beneficial to understand how they compare to international dimensions, especially if you’re working on projects that involve imported materials or collaborating with international partners. For example, in the United States, a standard size is the “2×4,” which nominally measures 50.8 mm x 101.6 mm but has an actual size of approximately 38 mm x 89 mm after processing. Here are the sizes we have available at Sabie Poles:
38 x 38 mm : 1.5″ x 1.5″ / 38 x 76 mm : 1.5″ x 3″ / 38 x 114 mm : 1.5″ x 4″ / 38 x 152 mm : 1.5″ x 6″ / 38 x 228 mm : 1.5″ x 9″ / 50 x 76 mm : 2″ x 3″ / 50 x 152 mm : 2″ x 6″ / 50 x 228 mm : 2″ x 9″
Our square beams are available in various sizes ranging from 60mm x 60mm up to 200mm x 200mm. For more information about our construction timber, please view our catalogue: Construction Timber
