Q: Why is it that treatment plants are allowed to continuing to treat imported unseasoned German spruce sleepers to UC3?
Commercially no one can ban what treatment plants accept for treatment, particularly because the situation with the treatment of spruce is not black and white. Only goods which are at a suitable moisture content should be put into the treatment plant, and every plant should be checking that as part of the pre process inspection checks. The information in BS.8417 suggests in most cases wood should be treated at a moisture content below 30%.
To me at the present time with the lack of wood available to the UK it seems counterproductive to be producing external timbers to only UC3 as there are limited uses in out of ground contact applications. Surely it must add more value and from a stock point of view be more sensible to get that wood to a suitable condition where it can be incised so it can achieve UC4.
Q: Is it acceptable to sell Scandinavian or Baltic KD C24 whitewood treated to a UC3 cycle as UC3?
This is rather like asking if its ok to sell C24 stamped wood without having any real evidence that it had been correctly graded.
As I said in the presentation the third stand of the TTF Action Plan is about each treatment plant having the accreditation and audit procedures in place. This will give treaters the confidence that the product quality in terms of the penetration and retention levels given in BS.8417 are being achieved within the acceptable limits on an ongoing basis. Remember, June 2022 is the end date for getting auditing in place. Advice from the TTF / WPA is to get that process started as soon as possible so you know where you stand.
We also simply cannot make generalisations about the treatment of whitewood. We know it is resistant to treatment, but there are differences between the species within this group. Sitka does not necessarily give the same results as European Spruce. Kiln drying is useful to get the MC down but in the process of ensuring everything is below 18% we see a lot of material at 12-14% which probably means the structure has closed up, and there is little chance of penetration. There will also be differences depending on the finish. Sawn will always allow greater penetration than PAR particularly if it’s a “glass” like finish.
Q: Why is it that the UK timber trade continues to pressure treat unseasoned timber with a FSP way over 30%?
We simply cannot make generalisations about the treatment of whitewood. The UK production sector probably has more experience in applying preservative treatment to Sikta Spruce than anyone else in the world. Where they are treating at moisture levels over 30% then that will be because the process audits they have in place are providing them with the confidence that is an appropriate moisture content for the products they are manufacturing, given the resource they are using.