When it comes to timber treatment, it’s important to ensure that your wood is protected from all forms of insects, wooddestroying fungi and other biological decay.

In order to do this, the timber industry use a ‘Use Class’ system, determining the level of treatment required in relation to the environment the timber is likely to be used in. The higher the class number, the higher the risk, and as a result, the stronger solution needed.

It is essential to specify the correct Use Class needed prior to the treatment, which is why timber treatment company WJ offer detailed guidance to customers to help them make the right decision. As specialists in low and high-pressure preservative timber treatments, they provide warranties of up to 15, 30 and 60 years to grant added assurance that timber is impregnated to the correct Use Class.

Not sure which class specification is for you? WJ has put together a useful guide to help you in the right direction.

Use Class 2

This Class is most commonly used for internal timbers like roof joists, which will remain dry and protected from the elements.

Often referred to as Vac-Vac or double vac, WJ’s Use Class 2 low pressure treatment offers long term protection for low to medium risk interior and weather protected exterior applications. Applied using a double vacuum process, the treatment is identified through the use of a yellow tracer dye to aid identification of treated stock.

The active ingredients in double vac provides robust protection against insects and fungi for the lifetime of the timber, when used in Use Class 2 environments. This low-pressure process avoids penetrating the core of the timber, meaning less water is absorbed. As a result of this, the treated timber withholds its original dimensions and natural moisture content effectively – making it the perfect solution for protecting construction grade timbers including CLS framing and joinery.

Use Class 3

This high-pressure process is suitable for use in external environments or when timber is to be used in contact with the ground. In these situations, there is a greater exposure to moisture and rainfall – which is an essential element that contributes to the development of mould and wood rot.

Ensuring that the preservative treatment penetrates the wood deeply to provide long-lasting protection, WJ’s water-based treatments provide excellent durability and mould resistance for almost all end uses, and are a popular choice when treating fence panels, decking, and cladding.

With a green dye to make it identifiable on site, Class 3 is often referred to as tanalith or tantalised timber. At WJ, Use Class 3 comes with a ten-year service life.

Use Class 4 (15 and 30-year service life)

Though Use Class 4 is technically the same process as Use Class 3, it offers greater protection to ensure that timbers which are in the ground, or in constant contact such as fence posts or decking joists, are protected. You can choose either the 15-year service life or the 30-year dependent on what lifespan you expect for your project.

About WJ

Founded in 2007, WJ Group provide innovative products and services to customers in the timber and leisure homebuilding markets. Having established an excellent reputation for being a forward-thinking, hardworking and entirely customer focussed business, they have a vision to be the market leader in high quality timber engineering and ethical timber treatments.

With treatment facilities close to ports in both Hull and Rochester, WJ is ideally located to service timber in both the North and the South of the UK. Working in line with BS 8417 Preservation of Wood Code of Practice, WJ ensure that each and every piece of timber they come into contact with is preserved according to the correct class specification.

WJ also offer a full deck board service to customers, anti-slipping your deck boards whilst treating with required preservatives – turning grooved boards into fully compliant, preservative treated and slip safe decking.

They are also equipped to support you with any fire treatment enquiries.

For advice and information on the options available, and the level of protection you may require, contact WJ at, or call 01482 338950.

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