In 2015, a benchmark outdoor exposure programme was established in Arnhem, the Netherlands, to provide data on how timber coatings perform after years in the elements. Now, 10 years later, the results are providing real-world evidence for joinery manufacturers, specifiers, and the wider coatings industry.
Accelerated weather testing in laboratories offer controlled conditions, but cannot easily replicate the complex conditions of real-world testing. For this test, panels were prepared according to EN 927-3, a European standard test for assessing the durability of coatings on wood over one year. They were mounted at a 45° south-facing angle, with sharp edges included to accelerate coating breakdown.
But one year was simply not enough to have any significant impact on the coatings. So, Teknos, a leader in industrial and architectural paints and coatings, and TDUK member Accsys Technologies decided to extend the testing period first to three years, then five years, and now 10 years.
Steve Ashton, Technical Services Manager at Teknos, explained: “Certain things simply cannot be replicated in a lab. To truly prove the performance of a coating, real-world testing is the only option.”
Teknos has also been running test sites for over 10 years in Denmark, the UK, and Malaysia to give further climatic perspectives. The trial included a wide variety of species and substrates: Meranti, Merbau, pine, thermally modified timbers, as well as Accoya and Tricoya. Both translucent and opaque coating systems were applied, at varying film builds, to capture how different systems performed in real-world conditions.
Some of the findings confirmed expectations – more dimensionally stable substrates, such as Accoya and Tricoya, proved reduced dimensional movement in the timber, put less stress on the coating and extended performance. Less easy to predict was the effect of care and maintenance. Regular cleaning, even with just water and a sponge, showed a marked improvement in surface appearance and performance over time.
According to Justin Peckham, Regional Head of Sales at Accsys: “One thing we’ve seen consistently here is that the coatings are lasting significantly longer on Accoya and Tricoya than on the other more unstable substrates. The more stable the timber is, the less stress the coating is under.”
For manufacturers, the results provide reassurance that coating specifications can be relied upon over the long term. For homeowners, it translates into better advice on care and maintenance, which could lead to lower lifetime costs. But for the wider industry, the biggest contribution may be confidence: evidence that warranties and performance statements are not simply marketing claims, but backed by real-world data.
The panels used in the test remain in the field. Some will be recoated and returned for further exposure, allowing the programme to continue building a picture of long-term performance. Product Development Specialist Alireza Boustani said: “On most of the samples we still see a very good coating performance even after 10 years. The idea is to continue outdoor exposure of those samples.”
Ten years is a milestone, but the work is far from finished. With more timber types, more coating systems, and more climates to assess, Teknos says outdoor testing continues to provide lessons that no laboratory can replicate.
