DOES YOUR EXTERNAL TIMBER CLADDING MEASURE UP ?
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info @ tdca . org . uk | 01977 558147 www . tdca . org . uk
EDITOR ’ S CHOICE
DOES YOUR EXTERNAL TIMBER CLADDING MEASURE UP ?
British standard BS8605-1:2014 , covers the manufacture of external timber cladding . It contains guidance on profile characteristics to help reduce the risk of movement related issues associated with the effects of moisture on wood .
Designers and architects need to be aware that not all external cladding profiles on offer comply with the Standard and if such issues are to be avoided , following the guidance represents best practice .
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Why size matters
Timber absorbs moisture from the air . Varying seasonal levels of moisture in external wood cause it to move , i . e . expand and contract across the grain , so in terms of cladding boards it affects width and thickness .
Width to thickness ratios for all profiles is set within the range of 4:1 to 6:1 in the Standard , although more than 6:1 is possible
A case where incompatible species and profile specification has resulted in movement issues ( medium movement Scots Pine , T & G : 144 mm wide with an 8 mm tongue width ).
with modified wood Accoya ® due to its ‘ very small movement ’ classification . Interlocking profiles such as Tongue & Groove ( T & G ) can be more problematic and here the standard limits board width to 125mm , unless very small movement timber is used . When boards are too wide and / or tongues too small , disengagement is more likely to occur as the timber expands and contracts and the cladding can pull away from the wall .
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From cladding boards and membranes to coating solutions and specialised fixings .
NB : There are always exceptions to the rules . Profiles which are technically non-compliant may be acceptable if there is compelling evidence to support fit for purpose performance .
For more advice , visit www . tdca . org . uk or call 01977 558147
Accoya : modifed wood
Timber Coaters Ltd
CladMark schemes require a full business audit and assessment followed by annual surveillance audits by the TDCA .
The Timber Decking & Cladding Association is an independent , not-for-profit technical and advisory trade body . Recognised as the authoritative source of expert opinion in the UK .
Get in touch and find a supplier today
info @ tdca . org . uk | 01977 558147 www . tdca . org . uk
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