News has emerged concerning the specification of the new 30 year treatment in the wood preservation code of practice, BS8417:2014.
The British Standards Institute, BSI published an updated version of this code of practice designated BS 8417:2011+A1: 2014 back in May 2014. Those specifying or buying treating wood for highways contracts or high quality fencing applications will be affected the most by these developments.
What is the BS 8417?
The BS 8417 is a ‘book’ of guidelines for the preservative treatment of wood. It is there to help protect wood products against bio-deterioration in end-use situations. From these recommendations, you can decide whether or not treatment is necessary and what type is needed.
What has been changed?
It is now required that the 30 year desired service life category with BS EN 599 type preservatives, exposed heartwood faces are penetrated to 6mm in addition to sapwood penetration requirements. Please do note however that this does not apply to creosote treated wood conforming to BS EN 13991.
What is the reason behind this adjustment?
There has been a growing awareness around variability in the natural durability of plantation grown commercial wood species. This has highlighted concern over the performance of longer service life sawn posts as they may be compromised by exposed heartwood surfaces. Theses surfaces may be under-treated because they are resistant to preservative penetration.
How will the new requirements be achieved?
Because penetration into a material like wood will inevitably be variable, an Acceptable Quality Level (AQL) is applied to penetration requirements within BS 8417.
Currently the typical AQL for resistant species is set at 25%. The enhanced heartwood penetration required within that allowance for a 30 year desired service life is only needed to be visible in 75% of the exposed surface area of that heartwood.
One technique said to be used in the past to help enhance preservative penetration in resistant species is Mechanical Incising. However, anything that results in reaching the 6mm heartwood penetration requirement can be used.
Find out how to access BS 8417:2011+A1:2014 Code of Practice by visiting the official BSI website.