The TDCA recommends that only timber capable of providing a minimum service life of fifteen years should be used. This means selecting:
- a hardwood species that is classified as being naturally "very durable" or "durable" or in some cases 'moderately durable'; or
- a softwood species that has been industrially pressure treated with a wood preservative approved under UK Government regulations to the correct standard for its end use
- a low durability softwood or hardwood species that has been modified with heat (thermal) or chemical treatment to improve its durability
Softwood is used a lot more for decking because it tends to be less costly and easier to work with than hardwoods. However the rich attractive colours of some hardwoods add greatly to their appeal. Naturally durable hardwoods are usually higher in density than softwood and their impact and abrasion resistant properties are reasons why they are used on commercial projects that have a lot of heavy use.
Properly constructed decking using naturally durable species or appropriately treated low durability species can provide an equivalent performance. Pressure treated softwood species are commonly used for the substructure of decks irrespective of the deck board material. British / European Standards allow you to specify pressure treated softwoods with a 15, 30 or 60 years desired service life. The industry default specification is 15 years. If you want longer than this you will often need to specifically request it. Some suppliers offer long-term warranties for their decking components. Always ask for written confirmation of what standards have been met for any timber you purchase.
The TDCA supports all initiatives that provide reassurance that timber materials used in decking have come from sustainable forests.