Grading Battens
Are Roofing Batten Standards that Complicated?
Not if you buy the correct timber!
There is controversy raging about grading battens and whether it is practical
to grade on site. What is important is that battens need to be graded.
Many features need to be assessed when grading battens. These include knots,
wane, slope of grain, fissures, rot and decay, insect attack, dimension and distortion.
Some of these are easier than others to assess. Some are impractical or difficult
to grade for on site.
An understanding of how the batten is produced is fundamental. Battens can either
be produced from ’sideboards’, (timber from the edge of the log, which is the
recognised method) or from the centre of the log, the latter often using small
logs. These are important distinctions and they have a significant impact on the
batten’s strength and stability.
Grading timber from ‘centre-cut’ battens is complex. The knot patterns and groups
require training to assess. Measuring slope of grain is difficult as there is
often significant disturbance around the knots. Batten cut from the centre is
also more prone to distortion as tensions are released in the timber. In addition,
testing at the BRE has found centre cut material to be less dense and weaker than
sideboards.
Ideally the roofer should be presented with a fully graded product that requires
no grading on site. It should not be the roofer’s responsibility to grade battens.
However, there is not sufficient factory graded product available in the UK market.
To assist the NFRC has produced Technical Bulletin TB33 which sets out the options
for the roofer, including grading on site.
It also should be noted that many battens marked ‘BS 5534’ have not been graded.
It is important to check the method of grading and if there is any recognised
Quality Assurance scheme in place.
THE OPTIONS
John Brash offers three options to the roofer:
JB-RED, JB-GREEN and JBI.
The optimum solution is to use JB-RED. This batten is graded and ready to use.
JB-GREEN and JBI are two high quality options suitable to grade on site.
