6 ways to get it right first time.
Timber decking is an increasingly popular surface used within many public spaces, from walkways and bridal ways to bars and restaurants.
But, selecting the right type of decking depends on many different things; treatment, strength grade, profile, and slip risk. Below are some of the common considerations and how to make the right product choice.
Many facilities and estate management professionals will come across the remedial works required for poorly specified decking. Some of you may even encounter more than one of the problems:
- Grooved boards that have worn before their anticipated service life is due to incorrect specification.
- Boards that do not provide enough anti-slip provision, with make-shift anti-slip through the use of chicken wire.
- Antislip provision that wears off before the end of its anticipated service life.
- Antislip provision that causes a trip hazard.
- Grooved boards that attract and accumulate debris and dirt that prove difficult to keep clean.
Repairs and replacement may be costly but the cost to the business while remedial works takes place can be significantly more than the works itself. Below are the 6 key ways to get decking applications right first time.
1) Location, location, location
Where will the deck boards be used? Country rural applications have very different requirements to deck boards for urban environments. Waterways and wetlands suit boards with a high level of antislip however, these boards can be difficult to walk on in urban footwear. For urban areas where consideration is required for pushchairs, wheelchairs high heeled shoes and trip risk with changes of level, a smooth non-slip board is more suitable.
Play it safe.
Country rural = JB Anti Slip Plus® a smooth board with strips of coarse aggregate for the Anti-Slip strips (see slip risk for number of inserts).
Urban = JB CitiDeck® a smooth board with a less abrasive aggregate for Anti-slip strips.
2) Meeting Part M
Timber decking can provide an excellent solution when designing to, and interpreting Part M of the current building regulations.
To help meet Part M, a smooth deck board should be chosen to give an easy comfortable ride when accessing the decking with a wheelchair. The non-slip inserts should give a low potential for slip, but at the same time, not be so slip resistant to cause a trip or stumbling hazard for those who are less able, and may have difficulty picking up their feet.
These inclusivity issues were highlighted in the work completed within the Olympic Park, where an average PTV (pendulum test value or ‘slip risk’) value of 48 was targeted. Typically, tarmac and concrete pavers fall in the 45-55 range, JB CitiDeck, a smooth non-slip deck board (with a finer aggregate non-slip insert), was designed to match this.
Recommended spans are set to ensure a maximum 3mm deflection so again, there is no trip hazard.
Timber decking provides an easy way to create access ramps into buildings. In addition, raised timber decks & balconies can provide additional outdoor living space with no changes in level from inside to out.
When designing ramps, to meet the requirements of part M, the slope should be no more than 1 in 20.
Decking can also be used to highlight changes in either level or surface – Use colour, ideally yellow, to mark changes for the visually impaired.
Indicate start and finish – A change in walking surface is required to indicate start and finish. This can be indicated by using castellated boards, or by a change in the anti-slip insets to show a difference.
Play it safe.
Use JB CitiDeck for the benefits of an anti-slip deck board for inclusive access
3) Slips and Trips
What level of slip resistance is required? Will standard deck boards without any non-slip performance perform in application?
It’s safe to say that any commercial decking project requires some slip resistance, but how do you get the optimum performance without paying for extra protection you may not need. If you install standard boards you run the risk of having to fit anti-slip protection retrospectively (which is never as effective) or replace the boards completely.
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 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.)
Play it safe.
Food service, event and hospitality areas = JB CitiDeck® a smooth board with a less abrasive aggregate for anti-slip strip.
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 of timber absorbs 1 tonne of CO2.
- Timber energy is CO2 neutral (only the CO2 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/
