On the Cover PLAY IT SAFE.


Standard commercial slip risk = 2 anti-slip inserts. High slip risk = 3 anti-slip inserts.


4. Treatment and Performance


Timber decking is preservative treated as standard, but some applications require additional performance. For most applications Use Class 3 is ideal. This specification is for exterior use applications, out of ground contact. In marine environments (not in permanent salt water contact), or where there is likelihood of regular contact with water and/or ground contact (even a hot tub would be included) it is recommended to specify Use Class 4.


It is also essential to check the other elements of the deck. Posts are invariably in ground contact and Use Class 4 is necessary. Care must be taken with joists. Often Use Class 3 is sufficient but where a joist is used on a balcony or flat roof, it is in ground contact and therefore Use Class 4 is required. Preferably look for a treated timber with WPA Benchmark accreditation. This gives assurance that 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. John Brash 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 contact /wetland or marine environment = Use Class 4. Decking as main walkway or exit = fire retardant treated.


5. 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 set out within BS 4978:2007+A1:2011 but how do you know which grade to use? 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


Building & Facilities Management – June 2014


requirements. C24 is a more demanding grade, requiring fewer and smaller knots than in a board graded to C16. The main advantages of using C24 graded deck boards are firstly, that in the same section as a board graded to C16 a wider rafter centre can be used or, a smaller deck board section can be used on the same centres. Most deck boards aren’t graded. Whist 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.


PLAY IT SAFE.


Buy graded deck boards. Standard decks with small joist span = C16. Bridges, balconies and walkways with a wider joist span = C24.


6. Maintenance and Cleaning


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 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 CitiDeck with a combination of smooth low and less abrasive grit.)


Timber decking - A sustainable solution


Natural timber decking has the lowest embodied energy of any mainstream building material and the Northern coniferous forests of Scandinavia provide a managed material to deliver a more sustainable product. Timber decking should also be procured with full chain of custody, either with FSC or PEFC accreditation and also comply with the European Union Timber Regulations. Correct specification to give a full service life in addition to the environmental benefits, can deliver a truly sustainable hard landscaping solution.


Carbon facts for timber: • Every 1m3


1 tonne of CO2


of timber absorbs .


• Timber energy is CO2 the CO2


• neutral (only absorbed is returned back to the atmosphere)


There is little waste in manufacturing, as the by- products can be used for energy generation in bio-mass power plants, which can be used to generate power for the site or the grid.


To find out more about correct specification and use of timber decking for the external environment book a CPD at www.johnbrash.co.uk/request-cpd/


PLAY IT SAFE. Food service, event and hospitality areas = JB CitiDeck®


a smooth


board with a less abrasive aggregate for anti-slip strip.


on the cover 15


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