Stage 1: Literature Review

Literature review of alternative wood preservative types to select several which appear to be the most efficacious and most likely to be permissible for ‘Use Class 4 timbers’ (i.e. those with ground contact) under existing and future EU pesticide directives. This selection will be based on:

• Proven anti-fungal efficacy

   

   

• Longevity of anti-fungal effect (leach resistance etc.)

   

   

• Absence of negative effects on treated timber physical properties (e.g. strength, conductivity, inability to take spikes)

   

   

• Environmental profile

   

   

• Simplicity of pole treatment (use of existing plant, seasoning requirements etc.)

   

   

• Potential for upgrade of anti-fungal longevity using supplementary products

The review will include research papers, scientific texts and web searches for new preservative types being promoted by existing companies for Use Class 4 and other timbers. Contact will be made with pole treatment organisations to determine whether efficacious alternative products are already being considered and for what reasons. In addition, the efficacy of existing alternatives to creosote in other countries will be examined.

Stage 2: Accelerated Testing

The construction of a fungal cellar facility – microbiologically active soil bed, elevated temperature, elevated humidity and rainfall simulation – for accelerated testing of timbers treated with the selected preservatives under simulated field conditions to determine whether the literature claims of anti-fungal efficacy are borne out by test comparisons with creosoted timbers (high and low retention) under conditions representing at least 20 years of UK field exposure. Up to 600 samples can be accommodated, 500 are expected.

This project will potentially provide at least one novel preservative type that can replace creosote with or without supplementary products (e.g. ground-line wraps). Reduced concentrations of creosote will also be investigated and performance compared with controls, to include at least creosote and copper-chrome.

Stage 2 Extension:

The project has been successful in building an effective fungal cellar facility and has demonstrated the capability to decay timber stakes to provide representative accelerated aging that would be expected in the field. To ensure best value of this facility, a project extension was agreed between all parties early in 2022 with the addition of the following scope:
1) Extension of existing timber stake trial by an additional two years. This increases the equivalent aging to 50-60 years in the field to provide improved evaluation of the preservative methods against existing products.
2) Addition of a round timber sample trial. This utilises the space made available within the cellar following the annual sample removal of the original timber stakes for destructive testing.

Stage 3: Final Report

Provision of a report detailing selection criteria, test results and recommendations including adoption of preservatives.

Benefits

• The fungal cellar is constructed and operated successfully (i.e. provides the required high temperature – high humidity environment.

   

   

• The test method is proven to be effective and valid.

   

   

• The environmental variables are held constant across samples during the test.

   

   

• The test provides estimated lifetimes for the samples, (whether preservatives, ground-line wraps or other treatments) with reasonable confidence intervals