DOES YOUR EXTERNAL TIMBER CLADDING MEASURE UP ?
DOES YOUR EXTERNAL TIMBER CLADDING MEASURE UP ?
EDITOR ’ S CHOICE
STAINLESS STEEL
SINKS • WORKTOPS • CABINETS • SHELVING
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 .
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 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 .
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
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 ).
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HR PROF is manufactured and approved to ISO 9001-2008
HR PROF THE ECO-FRIENDLY FIRE RETARDANT
· Water based - does not leach
· Allows wood to breathe naturally
· Internal / External application
· Colourless - Odourless
· EN 13501 – 1
· EN 16755 ( EXT1 ) according to EN 927-6
· Euroclass B-s1-d0
· Non Toxic - No Solvents
· BS 476 part 6 & BS 476 part 7
· BM TRADA ISO 9001 Certificate
· Meets the highest EU standards No HR Prof With HR Prof
®
Classification Reports & Certificates : Pine , Spruce , Scots Larch , Siberian Larch , Western Red Cedar , Oak , Thermowood , Birch , Birch Ply , and others , both Internal and External .
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