Hardwood decking can transform any space into a functional outdoor area that will retain its beauty and quality for many years to come. But to ensure this you need to follow certain guidelines regarding selecting the best-suited building materials do install a hardwood deck.
- Usually, 38 x 152 or 50 x 152 S.A. Pine H3 Timber is used, but this must be specified and designed by a competent person for safety reasons. For ultimate lifespan, a hardwood substructure such as Piqua or Garapa can be used but this is costly.
- Joists should be spaced at 350 to 450 intervals and off the ground.
- Noggins should be used between the joists to keep the joists square and rigid while CCA H4 treated pine poles or hardwood posts should be used to support the load and prevent the joists from deflection.
- Joist hangers are used to secure the ends of the deck to a wall but should not be relied on to be load bearing.
- There must be sufficient ventilation under the deck, particularly in damp areas when installing the substructure. Without ventilation, the decking planks, particularly the wider 140’s will ‘cup’ up. Cupping is caused by the underside of the decking planks remaining damp due to lack of ventilation while the top side dries.
The deck, screws and gaps
- Use a good quality decking plank. Kiln-dried (KD) is preferred over air-dried (AD).
- 4 to 5 mm gaps should be used for the 90mm decking plank while 8 mm to 12mm gap should be used for the 140mm plank. There will be some expansion & contraction depending on the season so appropriate spacing is essential. A proper spacer tool should be used not only to ensure consistency of the gaps but also to pull the planks perfectly straight.
- There must be at least 2 stainless steel screws per fixing at 350mm to 450mm intervals onto the substructure. Each stainless steel screw fixing should be 12mm in from the edge of the decking plank to prevent splitting. Under no circumstances can the deck plank be secured with one screw as this will cause the deck to ‘cup’. The holes for the screws should be pre-drilled 2mm oversized (otherwise decking ends will split), and the screws should be countersunk (otherwise when the deck shrinks the screws will be exposed).
- The stainless steel screw should be ideally a 5 x 60 but 5 x 50’s are used too. For the wider 140mm, we do highly recommend the 60mm. Please contact us to ask what the appropriate decking screw should be.
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