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Thread: compatibility question

  1. #1
    Associate Engineer
    Join Date
    May 2011
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    9

    compatibility question

    Im installing a galvalume metal panel roof. Supplied steel screws are used to hold the panel clips to the roof wood deck. Some of the wood is rotten and/or termite damaged. So, we have been replacing that with treated wood. I just heard that galvalume is NOT compatible with treated wood. Several sites did say that the peel and stick underlayment is sufficient barrier. However, that leaves the screws. Steel screws are NOT compatible with treated wood.

    Some sites say hot dipped galvanised is compatible with treated wood, however hot dipped is still zinc and zinc is NOT compatible with treated wood.

    What can i do, other then replace the treated wood?

    paul

  2. #2
    Associate Engineer
    Join Date
    May 2011
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    9
    I forgot to say. SS is NOT compatible with galvalume.

  3. #3
    Administrator Kelly Bramble's Avatar
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    Feb 2011
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    Bold Springs, GA
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    I just went to the galvalume folks website. I don't think they could be more vague or devoid of useful information. They do have a contact form on the website but they really need to provide some specifications.

    I know that for most metal roofs there is a rubber-ish washer between the screws/nails and the metal roof sheets. I suppose one can buy these at most consumer hardware stores. The rubber washers do eventually fail (20 years?).

    I have no idea on what the relative construction of the galvalume sheets are.. Aluminum over zinc or zinc over aluminum or some alloy of the two. If you can determine the composition they you might know the best approach to secure the sheets to the wood structure.
    Tell me and I forget. Teach me and I remember. Involve me and I learn.

  4. #4
    Project Engineer
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    May 2015
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    109
    The best reference that I know of for metal rooks is the Fabral Blue Book:

  5. #5
    Associate Engineer
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    May 2011
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    9
    i pulled the treated wood. just too risky.

  6. #6
    Lead Engineer Cake of Doom's Avatar
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    Aug 2012
    Location
    UK
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    411
    It sounds like Galvalume has probably been designed for use with Metsec or other proprietary type purlin systems. Sorry you had to rip out your new roof.

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