APF 2026 – BRITISH OPEN FENCING COMPETITIONS OPEN FOR BOOKINGS
LARGEST EVER UK FIELD TRIAL SHOWS TREATED WOOD SIGNIFICANTLY OUTPERFORMS UNTREATED
Interim results of the largest independent assessment of British treated softwood ever carried out in the UK demonstrate that treated wood for ground contact applications such as fencing can be relied on to provide a long service life.
The 10-year UK field trial of hundreds of wooden fence posts and test stakes was commissioned by the Wood Protection Association (WPA) and carried out by the Building Research Establishment (BRE) at two test sites: at BRE Garston, Watford, and Birnie Wood, Elgin, in the north of Scotland. It shows a substantial improvement in durability and resistance to decay when compared to untreated timber products.
The majority of the untreated wood posts at the sites have now completely failed due to fungal decay, with data suggesting an average service life of less than five years. The study also notably shows that posts made from larch are failing faster than any other species.
“These results clearly show that untreated wood of any kind is not fit for purpose for ground contact applications,” said WPA Director Neil Ryan. “Only wood that has been correctly treated gives the performance required to ensure long-term success.
The study also dispels the myth that larch is durable and can be used in this way without a preservative treatment.”
After 10 years, the preservative-treated posts in the trial are performing well, particularly incised spruce. Some opening of incisions and elevated moisture content has been noted, but without deterioration of the wood. Across all species and treatment types in the trial, there have been only isolated failures of treated posts. “This is not entirely unexpected after 10 years. These are clearly outliers on the bell curve of preservative performance, with others in the same species and preservative group rated zero — meaning they still have no visible decay present at all,” said Ryan.
The field trial was set up in 2015, with funding provided by WPA and a group of industry sponsors. WPA appointed BRE as independent agents to run the study.
Untreated timber after 10 years
The majority of the untreated posts have completely failed due to fungal decay, with an average service life of less than five years.
Treated timber after 10 years
The goal was to help develop industry standards, including BS 8417 and the WPA Code of Practice – to support WPA Benchmark quality approval schemes for treated wood, and to build market confidence in preservative-treated British softwood species. After the completion of the initial 10-year term, the project has been extended for a further five years.
