WPA Field Test Trials

June 24th 2020

In 2015 the UK Wood Protection Association (WPA) established a field trial to create an independent test of the performance of preservative treated fence posts with the aim of underpinning lasting confidence in preservative treated British softwood fencing as a reliable and quality product.

The trial has now been running for 5 years and the most recent round of inspections has yielded some interesting observations.

The performance assessment by the Building Research Establishment (BRE) of the timber after 5 years in ground contact has shown significant failure of untreated EN252 stakes and untreated fence posts at both the BRE Garston and the Birnie Wood sites.

The inspections of preservative treated fence posts, a percentage that are TANALITH treated, show no significant signs of change or deterioration. 

The fact that no significant signs of deterioration are observed after five years of exposure of un-incised, treated Sitka spruce (KD) and treated Larch and Douglas fir posts ensures confidence that all the other preservative treated material will be performing better. 

Early Observations

All treated posts are still performing well after 5 years service in two very different sets of ground conditions.

This clearly contradicts the anecdotal ‘conclusions’ being drawn by some in the fencing sector, following the widespread switch from CCA to Copper Organic preservatives 10-12 years ago, that early failures of posts after 3-4 years were simply due to the inferior performance of the new preservatives. Clearly there must have been other factors involved.

More details on this project and the results of the 5-year inspection can be found in a WPA Information Sheet, available for free download from the RESOURCE CENTRE of the WPA website – under Preservative Treatments > Research.

You’ll also find much more information on all matters wood protection.