Treated Timber Installation Guide

Why Treat Timber?

Timber, a timeless choice for construction and outdoor projects, requires thoughtful care to ensure its longevity. Preservative-treated timber is a popular choice for external projects to protect against decay and insects, but without proper precautions, its lifespan can still be compromised. In this guide, we'll explore the current best practices for extending the lifespan of preservative-treated or tanalised timber, discuss the reworking of treated timber, and delve into best practices post-installation.

Selecting Quality Treated Timber:

The foundation for a durable project lies in the selection of high-quality treated timber. Ensure that the timber is treated with proven preservatives like copper-based solutions, which have a track record of resisting decay and insect damage. Always purchase from reputable suppliers to guarantee the effectiveness of the treatment by treating the wood under pressure to prenetrate the wood deeper for a more effective application.

Proper Timber Installation Techniques:

A key factor in timber longevity is the installation process. Ensure that the timber is correctly positioned, with appropriate ground clearance to prevent ground contact, which can accelerate moistuew ingress & decay. Adequate ventilation is crucial to prevent moisture buildup, as damp conditions are a breeding ground for decay-causing organisms.

Regular Inspections and Maintenance:

Just as we schedule health check-ups, timber requires regular inspections. Periodically examine the treated timber for signs of wear, damage, or any areas where the treatment might have worn off. Promptly replace or repair any compromised sections to maintain the structural integrity and effectiveness of the preservatives.

Re-working treated timber:

Treated products are designed to be installed without modification. For this reason, re-working a pre-treated decking or cladding board, post, joist or batten during installation should be avoided if possible.

However, certain components need to be cross-cut to size, especially when you need a smaller piece of timber – just to finish off that last bit! That’s one of the advantages of timber, it is easily worked.

But by cross-cutting and even drilling, boring or notching the treated timber, you are likely exposing an untreated core, thereby breaking the ‘envelope’ of preservative protection.

Don’t panic – there is an easy solution.

Cut End brush-on treatment:

By giving each cut end two liberal brush coats of a suitable end grain wood preservative or protector you can maintain the integrity of the treatment. This also applies to areas which have been bored, drilled or notched - for example to accept fixings.

We would be happy to recommend a suitable product to use, shop here.

Appropriate Sealants and Coatings:

Enhance the protection of preservative-treated timber by applying appropriate sealants or coatings. Waterproofing solutions can prevent water ingress, reducing the risk of decay. UV-resistant coatings protect against sun damage, maintaining the structural integrity and aesthetic appeal of the timber.

Consequences of Neglect:

Neglecting the proper precautions for preserving treated timber can have significant consequences. Decay and insect infestations not only compromise the structural integrity of the timber but can also pose safety hazards. The financial implications of premature replacement and repairs make it imperative to invest time and effort in preventative measures.


In conclusion, the longevity of preservative-treated timber is within reach through conscientious practices. From selecting quality timber to vigilant maintenance and reworking, each step contributes to a prolonged lifespan. Neglecting these precautions, on the other hand, invites the risk of decay, structural compromise, and financial burden. By following these best practices, you not only protect your investment but also contribute to sustainable construction practices.

Remember, a little care goes a long way in ensuring that your preservative-treated timber stands the test of time.