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In this regard, numerous important considerations are worth
raising, specifically:
• All timber will weather to silver grey unless a regular
maintenance programme is adhered to. As weathering
occurs, surface ‘checks’ (fine cracks) are to be expected.
These do not impact the structural integrity of the boards.
• Dependent on the species, some initial leaching of
extractives can occur – this can stain painted or tiled
surfaces if they are directly below the cladded surface.
• Timber can also collect pollutants in the air, resulting in a
darkening of the surfaces.
• Less durable species should be surface treated to extend
their working life, but the cost of this and the regular
ongoing maintenance should be carefully weighed up
against the higher upfront cost of installing a more
durable maintenance-free option.
• Exposed timber will always experience seasonal
expansion and contraction. This ‘moisture movement’
should be expected and allowed for in the design. For
instance, if wider boards are used, with double fixings,
then oversized screw holes should be used to reduce
stresses on the timber as boards expand and contract with
the seasons. In addition, the client should have some
tolerance for natural variation in board width and
curvature as the timber moves.
• Boards should be fixed to battens made of treated pine or
marine ply, with spacings at 600mm or less. Ideally face
widths should be restricted to 135mm or narrower to
reduce the impact of inevitable seasonal movement.
• Stainless steel fixings should be used. Many timbers are
acidic and can be corrosive to ferrous metals.
• Although ‘shiplap’ and other common cladding profiles
are designed to form a moisture barrier, there should still
be adequate water drainage behind the boards. This will
come firstly from the cavity behind the boards because of
their elevated position on battens. If boards are being fixed
horizontally on vertical battens then there should be
sufficient drainage. If battens are horizontal then extra care
should be paid to ensure they don’t act as a moisture trap.
• Finally, unfinished timber cladding is best suited to large
exposed panels where you have less localised variation in
exposure to the elements. Using uncoated cladding under
projecting roofs should be carefully considered due to the
likely inconsistent weathering that will result.
Armed with these expectations and the work of skilled and
experienced installers, homeowners and developers have
never been in a better position to integrate the warmth and
natural beauty of timber cladding into their built structures.
Experienced timber merchants like Rare Woods are on hand
to ensure that high quality materials will always be available
to support these creative endeavours.