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Independent scientific study confirms treated wood performance
July 2022

In 2015 the Wood Protection Association in collaboration with the Building Research Establishment (BRE),commissioned a long-term controlled field trial of sawn and pressure treated British Softwood. The purpose was to test the performance of ground contact fencing timbers in a robust and independent study – the results of which would help to:

 

  • Gain valuable input into the future development of industry technical standards

  • Support the WPA Benchmark quality approval scheme for treated wood

  • Build lasting confidence in preservative treated British softwood species in this application as a capable, reliable and quality product

 

7 years on and the findings are very positive – they are showing that wood, preservative treated correctly for its end use, can be trusted to perform in the field.

Incised and treated Spruce posts at Garston and un-incised treated Spruce post at Birnie show no signs of deterioration after 7 years.

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Test criteria and results

There are 80 untreated posts and 600 treated posts (treated in accordance with WPA Benchmark quality criteria) each installed at two UK test sites with differing soil conditions. Matched samples of Spruce (un-incised and incised), Larch, Douglas fir and Pine are being tested. 

 

The BRE performance assessment of the timber after seven years has shown slightly different results from each site, but the overall outcomes are similar:

  • Significant failure of untreated fence posts at both test sites.

  • No significant signs of change or deterioration in the inspected treated posts at either site.

  • In the case of incised and treated spruce, there were no signs of deterioration at either site.

Conclusion Summary

7 years is a significant period in terms of drawing conclusions from the inspection data. The fact that treated posts are still performing well after 7 years’ service in two very different sets of ground conditions clearly contradicts the anecdotal ‘conclusions’ being drawn by some in the fencing sector

– that following the widespread switch from CCA to Copper Organic preservatives 12-14 years ago, early failures of posts after 3-4 years were due to the inferior performance of the new preservatives. Clearly, there must have been other factors involved.

An Information Sheet giving further details of the Year 7 inspection of this study can be downloaded from our Resources page