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Decking oil washes off boarding after rain

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  1. #1
    Apprentice (new member)
    Join Date
    Apr 2010
    Sydney, NSW

    Unhappy Decking oil washes off boarding after rain

    I had a covered outdoor deck built this summer by a professional deck builder. The deck has extensive boarding around it. All the boards, both from the decking and boarding, are Merbau and are coated in two coats of Intergrain Ultradeck. It was the choice of the builder to use this material. The coating was completed around 3 months ago. Is was dry and good weather when it was coated. After the very heavy rains of this weekend I have now noticed that the decking oil is staring to wash off and it is staining my new travertine pavers next to the boarding. Very annoying, to say the least!

    I raise this as I would like to have a better understanding of why this is happening? There could be many reasons: incorrect decking oil; too hot/too cold when coating; Incorrect material preparation; Not enough time between coats; etc.

    I am looking forward to a potentially unpleasant discussion with the builder, so all suggestions are welcome.

  2. #2
    4K Club Member Marc's Avatar
    Join Date
    Jul 2003


    I believe Merbau needs to weather a bit more before coating, but there are so many variable, that is hard to point fingers now.
    Real knowledge is to know the extent of one's ignorance

  3. #3
    1K Club Member
    Join Date
    Jul 2003
    Sunshine Coast


    Not certain if I have the right picture in my mind. By the surrounding boarding do you mean decking boards installed vertically surrounding the horizontal (walk on)decking. If so and if the vertical boards are above the pavers the issue can be that : if the back of the vertical boards are not coated and are still raw then when the rain found its way down the backside of the boards then it would have dripped the natural-tannin oils. Merbau-Kwila is famous-notorious for releasing a lot of red tannin . I see this often when inspecting decks for restoration. Even with the horizontal timber if the rain was blown onto the covered deck and the top of the wood is coated but perhaps the side of the boards are not as well coated and water has a habit of going down the sides of the boards & rolling onto the underside of the boards. This will also contribute to many red drops of red tannin.

    To stop this tannin the boards must be coated on all 4 faces. Even doing this will not offer a 100% guarantee against bleeding but will help. As Marc said some weathering can help but in my experience the weathering process can cause more issues than are wanted.

    Hoping this might be of some help

    good luck

    jimj restore-a-deck.com.au

  4. #4
    4K Club Member ringtail's Avatar
    Join Date
    Sep 2009


    Like Jim, I'd be putting money on tannin bleed.

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