25
Is your timber specification fit for purpose?
Janet Sycamore of the Timber Decking and Cladding Association discusses why and how the details of timber protection needs to be embraced to ensure specifications are always fit for purpose
That’s according to a recent survey of architects by the Wood Protection Association (WPA). The findings of this survey came as no surprise to the Timber Decking and Cladding Association (TDCA), which has long held the view that poor specification of preservative and fire protection treatments leads to compromised timber performance. The TDCA and WPA exist to support architects and specifiers in their correct choice of timber. This specialist knowledge and expertise must be embraced throughout the industry to ensure specifications are always fit for purpose.
K
The extent of natural durability How to correctly specify timber for durability is a common question asked of the TDCA. Some timbers (mainly hardwoods) offer natural durability. They can withstand outdoor and ground contact for a determined service life without coating or treatment.
BS EN 350: 2016 provides durability classifications for different timber species. There are five classes, Class 1 being the most durable. A table detailing the expected service life of different species for various locations can be found in BS8417 (the British standard for wood preservation).
When to specify preservative treated timber
If you’re intending to use a softwood timber outdoors, some level of factory preservative treatment will most likely be necessary. For outdoor use, timber is generally treated to Use Class 3 or 4 dependant on application, be it above or in ground contact. A proven method for decades, pressure
ADF AUGUST 2019
treatment involves impregnating the decking or cladding timber with a wood preservative (most commonly, copper- based). It’s a tightly controlled procedure with checks for the level of treatment and how far the preservative penetrates. BS8417 details the specific requirements for timber preservation.
Not only will the right specification of treatment achieve the desired service life, it will also lock up carbon for longer and enable less durable timbers to be effectively used for longer-term applications; an environmental boon.
Modified woods are a more recent innovation gathering pace. They employ processes that physically alter the timber
nowledge of fire protection terminology in the design and build sector is woefully low.
VODAFONE BUILDING
Glenalmond Abodo cladding to the building in Christchurch, New Zealand is made from thermally modified softwood
WWW.ARCHITECTSDATAFILE.CO.UK
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36
