Structural treated pine help please

Not sure if anyone would know anything about this, my dad bought 4 lengths of 4.2 metre 190 x 35mm H3 treated pine from Mitre 10 to replace rotted structural beams on an outdoor deck.

3 of them seem fine, but one of the lengths has around 3-4 knot holes which are at least an inch in diameter, one of them is probably about 3.5cm, on the long edge of the timber.

He was wondering if it was okay to use, or if it shouldn't have been sold like this in the first place. I can't seem to find any Australian standards for this on the web.

Thank you for your help :)


  • +7

    Pretty sure it is up to the buyer to inspect the timber and decide if it is fit for purpose prior to purchasing, or signing/accepting if delivered.

    I believe lumber only has to meet standards in relation to how it is treated, not its knot count.

    It is likely fine to use, just ensure your joints are strong and not putting stress on the areas affected.

    • My understanding is timber merchants offer "grades" of timber.
      The better timber attracts a premium.
      Its not uncommon for hardware stores to carry the more cost competitive option to compete on price.

      If your father is in doubt I would imagine Mitre 10 will be happy to switch it out.
      Do not be scared to fish through a pack of timber for the best pieces.
      Take a note of how wet the pine is. As the pine drys it may warp.

  • +2

    Pics would help. Depends on how far through they go. I always select the timber and make sure there are no bad knots, otherwise workers don't give a shit and just give you what ever crap. You should be able to take it back and swap for another piece.

  • Thanks heaps for the help! He definitely should have selected but he had them delivered straight from the warehouse. I think it'll be fine :)

  • knots don't necessarily mean the timber is not fit for purpose, it depends on the specific knots and the loads it will be subject to. Most pine used for house framing has knots in it.

  • Its not only the size, but the location of the knots. Knots that are near the centerline should not be a problem, but if they break out to the surface, the effective cross-section is reduced.
    It may still be possible to get away using these by carefully placing the knots on top, so that they are in compression.

  • You'll be fine, relax.

  • 4.2 metre 190 x 35mm H3

    Are these structural timber and will they installed in the ground?

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