Often Use Class 3 is sufficient but where
a joist is used on a balcony or flat roof it
is in ground contact and Use Class 4 is
required. Preferably look for a treater with
WPA Benchmark accreditation. This gives
assurance the product is correctly treated.
Some ‘off the peg’ components may not
be treated for decking applications.
Where decking forms part of an exit,
either a fire escape or main exit it should
be treated with an exterior fire retardant.
Although not classified as having
preservative properties this process gives
enhanced biological durability. Marley
Eternit FTX Exterior Fire Retardant treated
deck boards have a 30 year desired
service life when used in Use Class 3
applications. (Exterior, out of ground
contact).
Play it safe…
Above ground applications = Use Class 3.
Ground/water contact = Use Class 4.
set out within BS 4978:2007+A1:2011
but how do you know which grade to use?
C16 or C24?
Boards graded to C16 are generally
recommended for most applications and
if the correct spans are used this is usually
the most cost effective option that will
still meet the performance requirements.
You should find our article explaining the
difference between C16 and C24 helpful.
Most deck boards aren’t graded. Whilst
failure is unlikely key areas such as
deflection which consequently could
cause a trip hazard (or even give the
deck a ‘bouncy feel’) should be carefully
considered. All recommended span tables
are based on specific grades of timber.
make the deck a slip risk? It’s important
to make sure that decking that will
require regular cleaning is appropriate.
Use a smooth board and then choose
the relevant anti-slip solution (often JB
CitiDeck® with a combination of smooth
low and less abrasive grit.)
Play it safe…
Food service, event and hospitality areas
= JB CitiDeck® a smooth board with a less
abrasive aggregate for Anti-slip str ips.
www.marleyeternit.co.uk
Play it safe. Buy graded deck boards.
Standard decks with small joist span =
C16. Bridges, balconies and walkways with
a wider joist span = C24.
Maintenance and Cleaning
Decking as main walkway or exit = fire
retardant treated.
Strength and Support
All timber decks, whether domestic or
commercial, are designed to carry specific
loads; these include both uniformly
distributed and point loads. The grade
rules for the use of structural timber are
Timber decks are a low maintenance
solution, aside from an annual clean
with a stiff broom they can be left
to weather naturally. However some
applications, such as decking in food
service or hospitality areas require further
consideration. How easy will it be to
clean food and debris from the grooves in
castellated decking. Could trapped debris
Landscape & Urban Design
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