Stricter guidelines have been drawn up by the UK Timber Grading Committee to help certification bodies do a better job.
The committee has decided that certification bodies must ensure that ‘licensees’ or approved companies have documented quality control systems in place. It has also ramped up standards on the sampling required to measure moisture content.
Previously the sample percentage was a minimum of four readings for the first 100 pieces in a batch and thereafter one reading per 50 pieces up to a maximum of 10 readings per batch. However, investigations demonstrated that there were insufficient readings taken from timber lots, leading to claims of unsuitable timber being used.
The new guidelines advise that for lots up to 150 pieces, the sample size will be 20%. For lots of over 150 pieces, the following table will be used:
151-280 = 40 pieces
281-500 = 50 pieces
501-1,200 = 60 pieces
1,201-3,200 = 70 pieces
>3,201 = 80 pieces
The moves have been welcomed by BRE Certification, which claims to be the only body to require assessment of quality systems as part of the certification process for visual strength grading of timber.
