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Thread: Duct Mastic

  1. #1
    Join Date
    Aug 2007
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    Confused Duct Mastic

    Is there a way to put duct mastic paste on duct neatly? I put it on some residential installs and the customers seem not to like it so much. I try to put it on as neat as possible but for some reson people like the foil tape better.
    Any suggestions?

    Thanks

  2. #2
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    Put a line of duct tape about two inches on each side of every joint you are going to mastic, because you only need to mastic the joints and when you are done pull off the duct tape for a nice clean line. Also make sure you put membrane down before you use the mastic, it's worthless without it.

  3. #3
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    Masking tape.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  4. #4
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  5. #5
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    Quote Originally Posted by adrianf View Post
    I'm pretty sure we were talking about mastic..... not tape

  6. #6
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    Quote Originally Posted by grasshopper1 View Post
    Put a line of duct tape about two inches on each side of every joint you are going to mastic, because you only need to mastic the joints and when you are done pull off the duct tape for a nice clean line. Also make sure you put membrane down before you use the mastic, it's worthless without it.
    What is membrane? And are you talking about the kind of tape that painters use to cut the houses with?

  7. #7
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    Jan 2007
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    N.E. Ok.
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    That tape has a butyl compound with aluminum backing, good stuff.

    What are you refering to as membrane.



    Quote Originally Posted by grasshopper1 View Post
    I'm pretty sure we were talking about mastic..... not tape

  8. #8
    Join Date
    Mar 2007
    Location
    Pensacola, FL
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    When you say duct, are you referring to Duct Board or Flex Duct? When applying mastic to ductboard, you should have used UL 181A tape underneath it first, not sure what the membrane is mentioned before. Where are you installing this? If in a basement where homewowners will see it daily, I might see their concern, but if in an attic, why would it matter?

  9. #9
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    May 2007
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    Quote Originally Posted by ejgibbs3 View Post
    When you say duct, are you referring to Duct Board or Flex Duct? When applying mastic to ductboard, you should have used UL 181A tape underneath it first, not sure what the membrane is mentioned before. Where are you installing this? If in a basement where homewowners will see it daily, I might see their concern, but if in an attic, why would it matter?

    Right, wrong or indifferent mastic is not listed or approved to be applied over the 181a tape and some jurisdictions will turn down installations done this way.

    http://www.braunindustrialsupply.com...cts/585-ds.pdf

  10. #10
    Join Date
    Aug 2007
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    339

    Talking

    Quote Originally Posted by ejgibbs3 View Post
    When you say duct, are you referring to Duct Board or Flex Duct? When applying mastic to ductboard, you should have used UL 181A tape underneath it first, not sure what the membrane is mentioned before. Where are you installing this? If in a basement where homewowners will see it daily, I might see their concern, but if in an attic, why would it matter?
    I was talking about sheet metal duct. Also I was wondering if someone out there has taken any pictures of a neatly install duct system using the mastic paste on it that does not look crappy!

  11. #11
    Join Date
    Jul 2006
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    Virginia
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    Smile

    it should not look sloppy, but i would be more concerned about how well it is sealed than how pretty it looks

  12. #12
    Join Date
    Aug 2006
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    SFL
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    80
    this is what a refer to as membrane

    http://www.rcdmastics.com/Glasscoat.asp

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