Choosing the right timber is only part of ensuring a successful, long-lasting project. Equally important is selecting the correct timber treatment level for the environment in which the timber will be used.

Timber treatment protects wood from insects, fungi, decay, and moisture, significantly extending its lifespan. In South Africa, treated timber is classified into five hazard classes, ranging from H2 to H6, with each level designed for specific applications.

H2 – Internal use (Low hazard)

H2 treatment protection for timber that is used internally and is protected from direct exposure to moisture.

Typical applications include:

Interior wall framing
Enclosed roof structures and timber trusses
Interior mouldings such as flooring and ceiling
Covered building applications

Options on treatment chemicals are Vacsol Azure H2 (spirits based) and CCA (Water-based)

H3 – Exterior Above Ground (Moderate hazard)

It is designed for timber that is exposed to the weather but is not in direct contact with the ground. Treatment chemical is CCA (water-based)

Ideal for:

Pergolas
Deck substructures
Exterior framing
Carports
Fencing and fencing rails

At Somerset Timbers, our structural timber is treated to H3, providing greater protection than H2-treated timber often supplied elsewhere.

All our Pine decking and CCA treated exterior products are treated to H3 specification.

H4 – Ground Contact (High hazard)

H4-treated timber is specifically designed for applications where timber is in direct contact with the soil.

The higher preservative retention provides long-term protection against decay and insect attack.

Common uses include:

Fence posts
Landscaping timber
Retaining walls
Garden structures

We treat all our poles to CCA H4 for this use.

H5 – Heavy Duty Ground Contact (High hazard)

H5 treatment is intended for demanding structural applications where timber is permanently exposed to severe ground contact conditions.

Suitable for:

Specialized agricultural structures
Heavy retaining systems
Structural support posts

This is not an off the shelf specification and minimum quantities and lead times apply.

H6 – Marine Environments (High hazard)

H6 offers the highest level of preservative treatment and is specifically designed for timber exposed to marine conditions.

It provides protection against marine borers, decay, and extreme environmental exposure.

The process is a dual CCA and Creosote treatment process which requires careful timber selection and drying time betwene treatment to provide this level of protection.

Typical applications include:

Jettys
Piers
Harbour structures
Marine piling

This is not an off the shelf specification and minimum quantities and lead times apply.

Why Choosing the Right Treatment Matters

Using the correct treatment level ensures your timber performs as intended throughout its service life. Selecting timber with insufficient treatment for its environment can lead to premature decay, structural failure, and unnecessary replacement costs.

Whether you're building a deck, pergola, roof structure, or fence, matching the treatment level to the application is essential for long-term durability.

Somerset Timbers' Commitment to Quality

At Somerset Timbers, we understand that every project has different requirements. That's why we offer a comprehensive range of treated timber solutions and expert advice to help you choose the right product for your application.

If you're unsure which treatment level is best suited to your project, our experienced team is always available to assist.

Visit our showroom or contact Somerset Timbers today to find the right treated timber for your next project.