Hardwood Decking Tips

Hardwood Decking Tips

Hardwood Decking is very popular in South Africa. From all the options available hardwood decking still rates highly for durability and aesthetic appeal.

Online Building in Cape Town supply structural pine and structural hardwood such as Piqua, Garapa and Balau as well as A Grade hardwood decking in Balau, Macaranduba, Garapa and Ipe. Here are some tips for installing a hardwood deck. This doesn’t cover all the ‘ins and outs’ but can be used as a good reference point.


  • 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.

The deck and securing thereof

  • Use a good quality decking plank. Kiln dried (KD) is preferred over air dried (AD).
  • 3 to 4 mm gaps should be used for the 90mm decking plank while a 4 mm to 7mm 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 over sized (otherwise decking ends will split), and the
    screws should be counter sunk (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. Please contact us to ask what the appropriate decking screw should be.

For best results

  • We suggest with all decking; especially Garapa (cement stains Garapa) should be regarded as a finishing product so do not install it if paint, plaster or any other labor work is still to be done in the area.
  • Oil treatment should be used on the deck once the deck is installed and cleaned to help maintain the deck and minimize surface cracks, splintering, cupping and crowning. Please contact Online Building for advice on cleaning your deck and the best oils to use.
  • Lastly, it’s important to remember your timber deck is a natural product so as your deck weathers, expansion and contraction will happen and small cracks are likely to appear on the surface of your deck. This is caused by intermittent wetting and drying of the deck and is part of the character of the timber but has no structural affect on the deck what so ever.