Marketing Treated Timber

Changes to the TTF Code of Conduct

Since 2017, the TTF and the Wood Protection Association have collaborated to enhance the education and quality of preservative treated timber products.


At the TTF AGM on 17 November 2020, TTF members unanimously voted to implement the Preservative Treatment Action Plan into the TTF Code of Conduct.


As a result, Members must adhere to the guidance provided in BS8417 (2014) and the 2021 WPA Code of Practice: Industrial Wood Preservation for the choice, use, and application of wood preservatives.


Members shall ensure that:

Point A. Preservative treated wood is being accurately and unambiguously specified/purchased, for use or resale, and is clearly identified at all points of the chain (on orders, internal stock movement records, and sales records) as fit for the intended purpose.


As a minimum this will require identification of the product as suitable for either:

1. Interior Use only – Use Class 2
2. Exterior use above ground – Use Class 3U
3. Ground Contact – Use Class 4

(Point A. To be implemented by all TTF members before the end of March 2021.)

Point B. Customers purchasing treated products from TTF members are provided with adequate information and, where appropriate, the training materials developed by TTF / WPA to be able to use and install those products safely and effectively.

(Point B. To be implemented by all TTF members before the end of March 2021.)

Point C. Preservative treated wood is being produced by or purchased, directly or indirectly, from a treatment provider whose operation has been assessed and approved under an independent and reputable accreditation scheme (e.g. WPA Benchmark in the UK, the Nordic NTR scheme or other similar).

(Point C. To be implemented by all TTF members before the end of June 2022.)

Use Class Guides (Point A)

To ensure Members understand the new requirements in the TTF Code of Conduct, the TTF, and the WPA have collaborated to produce Use Class guidance notes to ensure the successful implementation of the Preservative Treatment Action Plan.

Use Class 2

Use Class 3

Use Class 3c (coated)

Use Class 4

WPA Field Trials 5 year observations July 2020

Information and Training for your customers (Point B)

The TTF and the WPA have produced guides and training materials to help your customers understand the new requirements.

Buyers Guide to Preservative Treated Timber

Buyers Guide

Getting the right treatment Leaflet

Use Class

Use Class 2
Social Cards

Use Class 3
Social Cards

Use Class 4
Social Cards

Making the most of wood presentation

Treatment Operation Assessment and Approval (Point C)

This section aims to assist TTF members with timber treatment plants to operate a targeted quality management system and ensure that the quality of wood treated can be verified by an independent auditor. It also provides information to ensure that where members are buying treated wood the same criteria can be applied.

Guidance for Wood Treaters in the NTR Region

Achieving Compliance – TTF Action Plan

Why the action plan is needed

In 2017, TTF & WPA collaborated on a survey to identify the strategic priorities needed in order to grow demand for preservative-treated timber. The survey identified three priority areas for action:


1. To address the common failure to specify treated wood correctly;
2. To address the lack of understanding on how to correctly install and use treated wood;
3. To ensure independent verification of the treatment process.


Since this survey, the TTF has been working with the Wood Protection Association (WPA), Timber Decking and Cladding Association (TDCA), and British Standards Institute (BSI) technical committees to improve the quality and consistency of preservative treated timber products.


By improving this crucial part of the timber supply chain through stronger standards and clearer labeling of goods, we are helping to further develop the reputation and assurance systems that exist for preservative wood products, and ultimately helping to grow the use of wood in the UK.


The changes would raise the Use Class allocation for deck substructures, including deck joists, from a UC3 to a UC4 application. These changes would put us in line with the rest of Europe.

Let’s talk treated timber webinar

The TTF, Wood Protection Association (WPA) and Timber Decking & Cladding Association (TDCA) hosted a one-hour on-line event on timber treatments.


The event informed and updated members on the wide range of educational resources available our supply chain communications campaigns aimed at the builders merchant sector and at the fencing and landscaping market and was also updated on the TTF Action Plan.

Communications Campaign, Make sure it’s Use Class 4

To enhance the trust in the market and to support our members in educating their customers on the new requirements, the TTF, WPA & TDCA have launched the ‘Make Sure it’s Use Class 4’ campaign to promote the accurate description of treated wood to increase the public and merchants knowledge on the important differences and purposes between each Use Class.


This campaign stems from a survey conducted on behalf of the WPA and the TTF. The survey found 97% of merchants did not know that a specific class of timber treatment exists for timbers used in ground contact and only 3% recognised that a Use Class 4 timber treatment is needed for this application

As well as merchants, users of preservative-treated wood had very little understanding of what Use Class is and does.


  • When asked if there was a specific treatment specification for timber in ground contact, over 90% of people surveyed said they didn’t know.

  • When asked if they understood what ‘Use Class 4’ means, 72% said they didn’t know.

To help educate the public and merchants, we have created a series of posters and graphics that you can post on social media. Click on the images to download.

Preservative Treatments for Timber: Durability

All mature trees have an inner core known as HEARTWOOD surrounded by an outer layer of younger SAPWOOD. The sapwood is where the tree stores the nutrients essential to growth. These food reserves remain after the tree is logged and sawn into components.


The heartwood of some species contains naturally occurring chemicals that make it relatively durable – the ability to resist decay and insect attack. The degree of natural durability varies from species to species.


Sapwood on the other hand is a source of food for many species of fungi and insects and is always vulnerable to attack. The risk of an attack increases significantly if, for any reason, the moisture content of wood rises above 20% – for example, poor installation practice or maintenance, persistent condensation, or damp.


Some degree of sapwood is likely to be present in the timber we use for building, hence the precaution is taken to treat certain timbers with preservative prior to use.

Making the most of a valuable resource

Wood protection technology helps to optimise the amount of harvested timber that can be usefully gained from the tree. Timber preservatives for softwood materials provide tailored levels of protection from decay and insect attack – making the resulting wood more durable and offering reliable longer-term performance.


Making the most of timber resources in this way also reduces waste and reduces pressure on the more naturally-durable, but perhaps more scarce species.



Chemicals and the environment

The preservative industry is highly regulated and manufacturers continue to introduce innovative products that are better targeted towards the organisms we wish to control and more environmentally benign.


Wood protection formulations tend to chemically bind into the timber after impregnation and are not free to readily escape in service.


At the end of its service life, treated wood can be reused or recycled for approved applications or disposed of in a way that minimises any potential for environmental damage.


The benefits gained by using treated timber can be balanced against any relatively low negative impacts, especially when looking at the bigger picture – see Building with Wood.


For more information, head to our Preservative Treatments for Timber page.

Our Articles on Preservative Treatment