Guard against early joist failure

Guard against early joist failure

Timber Development UK and the Timber Decking & Cladding Association are working together to give merchants the resources they need to sell the correct components for timber decking.

As we head into what we hope will be another long, hot summer, homeowners across the country are looking to maximise these warmer months by improving and upgrading their gardens.

For many this involves creating bright, modern areas where friends and family can gather – with timber decking often playing a fundamental part of these newly landscaped spaces. The popularity of timber decking has exploded in recent years, with more households embracing the natural beauty of timber and how a well-constructed deck can transform a previously tired-looking garden space.

To get the very best out of these structures, and to make sure they will last for years to come, it’s important to choose the best components and to guard against some of the common mistakes builders and landscapers can make when it comes to building a timber deck.

Early joist failure is one of the most common problems experienced, but it’s easily prevented if builders make the right choices when purchasing materials. The emphasis is often on the deck boards and achieving the aesthetic that the customer wants, but it is just as important to consider the deck substructure, which includes posts, beams, joists, blocking and bracing.

These components form the foundation to the whole project, and if the wrong types of wood are used it can cause real problems. Merchants should always recommend pressure-treated softwood for deck substructure components to ensure a quality, long-lasting finish.

To be fit for purpose the timber substructure components must be preservative pressure treated to a Use Class 4 level of protection, irrespective of whether the material is in contact with the ground or not. This reclassification to Use Class 4 is a recent change that the industry is gradually adapting to, but many builders are still unaware of the change.

The availability of Use Class 4-treated joists in timber and builders’ merchant yards is increasing, especially through companies who are members of Timber Development UK and the Timber Decking & Cladding Association (TDCA).

The Timber Decking & Cladding Association (TDCA) is an independent, not-for-profit advisory organisation established to influence and promote good industry practice.

A campaign highlighting the importance of choosing correctly treated timber is currently being promoted throughout the timber supply chain – you can learn more at the Wood Protection Association

Getting the fundamentals right at the beginning of any decking or cladding project is key to both customer and seller satisfaction. For those looking for added assurances of quality, the TDCA operates the DeckMark and CladMark quality accreditation schemes, which cover products, suppliers and installers. They provide audited verification of compliance with good manufacturing and supply practices and sound installation techniques trusted by the TDCA and the wider industry.

If you would like your business to become accredited, contact the TDCA at for more information.

New Timber Decking Handbook

You can also find more information and advice on timber decking in a brand-new Timber Decking Handbook that is now available for merchants to download online. Published jointly by TDCA and Timber Development UK, the Handbook aims to provide definitive guidance for all specifiers, buyers and installers interested in using timber decking in their projects.

The Handbook offers advice on decking design and planning, material selection, installation and maintenance, as well as how to source timber responsibly and an outline of relevant UK Building and Planning Regulations.

Download your free copy at