Understanding of UC4 grows

Mystery shopper research among merchants shows that the supply chain’s understanding of Use Class 4 timber treatments has improved since 2020.

The Wood Protection Association (WPA), supported by Timber Development UK (TDUK), has long been fighting to improve knowledge of the different timber treatments and when they should be used.

It’s vital that merchants understand the different Use Classes, so they can sell their customers the right treated timber. Otherwise tradespeople may face issues such as poor performance, shortened service lives, and even potential dangers if, for example, the wrong timber causes a deck to fail.

But things are improving. In 2020, the WPA carried out mystery shopper research in the treated timber supply chain to investigate levels of awareness in relation to timber treatment with wood preservatives.

The research specifically focussed on ground contact timber and deck joists and the need for greater levels of protection with reference to the Use Class system. The results found a severe lack of knowledge among customer-facing staff, with poor and sometimes inaccurate website product information.

Following the 2020 research, the WPA, TDCA and TDUK united to create the ‘Make Sure it’s 4’ timber treatment campaign for ground contact timber products to raise awareness of the different Use Classes and their applications.

Three years on, the mystery shopper research has been repeated among a selection of national and independent merchants and retailers. This time around, the survey has also examined people’s knowledge of incising techniques.

The general consensus today is that knowledge of when to specify Use Class 4 (UC4) levels of treatment has grown significantly, but more still needs to be done to make sure buyers can be confident they are getting what they ask for.

Back in 2020 only 3% of those surveyed knew there was a specific treatment specification for timber that is in ground contact. By 2023, this figure has improved to 69%. This is a positive sign that more of the industry has an understanding of these key messages.

In 2020, when asked what Use Class 4 meant, 72% of those questioned did not know. This time, the percentage of those who had not heard of UC4, or who gave an incorrect description of what it was, had fallen to 47%.

Know your Use Classes

Exterior structural supports such as deck substructures now require treatment to a UC4 standard.

How can you make sure your staff are up to speed with timber treatments?

Make sure your staff know the right language to use when talking to customers. Terms like ‘green treated’ are considered too general and no longer acceptable.

The correct terms are:

  • Use Class 4 for timbers on or in ground contact
  • Use Class 3 for external timbers above ground
  • Use Class 2 for construction timbers within the building envelope.

Good practice around specific applications has also changed. It now states all softwood decking substructure components must be treated to Use Class 4, bringing the UK into line with standards set in other countries. So remember, not all treated timber is the same, and timber that is used for exterior structural support must also be treated to Use Class 4.

Establish a Benchmark

UC4 material is exposed to more challenging ground contact environments.

The WPA Benchmark quality accreditation scheme is designed to give purchasers greater confidence when sourcing preservative treated wood components.

The original scheme was developed by a task group comprising wood treatment companies, technical consultants, the major suppliers of preservatives and independent research consultants. This has since developed into a series of quality assurance schemes to cover each stage in the production of preservative treated wood-based materials.

The WPA Benchmark audit process focuses on verifying that an effective quality management system is in place that meets the criteria set out in WPA Quality Guidance Note 2 (QGN2).

Applicants must pass an initial audit and subsequent annual surveillance audits by providing evidence to demonstrate they are treating to industry standards.

Emphasis is also placed on the accurate specification of treated products and the description and labelling of goods. This includes the provision of adequate customer and end user Point of Sale information and training and where appropriate, guidance on the safe and effective use of treated products. Compliant companies are awarded WPA Benchmark Approved Treater accreditation.

As UC4 material is exposed to more aggressive ground contact environments (frequently wet), such components are subjected to even greater scrutiny. The business must demonstrate that a verifiable and consistent ‘Safe Relationship’ exists between preservative penetration and retention requirements and the more easily measurable parameters of the treatment process such as the impregnation process, solution strength and preservative uptakes. If all is in order, companies are awarded WPA Benchmark Approved Product accreditation.

Growing accreditation

2022 saw a marked increase in the number of businesses awarded a WPA Benchmark quality accreditation, especially from overseas. This is in part driven by TDUK’s preservative treatment action plan – point 3 stating: ‘TDUK members who supply treated wood, should ensure treated wood products are produced by treaters whose operation has been assessed and approved under an independent accreditation scheme, such as WPA Benchmark.’

Learn more

All WPA Benchmark accredited businesses are listed online at www.thewpa.org.uk

You can also learn more about preservative timber treatments and the different Use Classes at www.timberdevelopment.uk/resources/timber-use-classes


*  This article was originally printed in the May/June issue of Supplying Timber magazine.