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Community and Q&A

Delta Maxx Titan vs GAF Deck Armor

merlinm | Posted in General Questions on

We are evaluating permeable roof underlayments for a project on the border of zone 2 and 3. Roof is standing seam metal installed on floating clips with an air space between the metal and the underlayment. There will be several inches of closed cell insulation against the inside roof deck in the unvented and conditioned attic. 

Two of the underlayments being considered are Delta Maxx Titan and GAF Deck Armor. 

Would be interested in hearing about positive or negative experiences with either of these products. 

The Maxx Titan is considerably more expensive the Deck Armor. Has anyone here used both? 


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  1. user-2310254 | | #1

    Hi Merlin,

    I will give your post a bump. The clips are attached to the roof sheathing, and the rigid foam is on top of the roof sheathing. Is that correct? If you are taping the edges of the foam, can't that serve as your moisture barrier? What is the underlayment protecting?

  2. merlinm | | #2

    Thanks for the bump, Steve.

    There will be closed cell foam against the inside of the roof sheathing. No exterior insulation on the roof. Exterior stack: roof sheathing - underlayment - air gap provided from floating clips - standing seam metal roof.

  3. user-2310254 | | #3

    Hi Merlin,

    Maybe one of the experts will chime in with some input. In the meantime, have you considered going flash and batt on the roof insulation? You could install one or two inches and then make up the balance with air permeable. Would be cheaper and greener.

  4. aaronbeckworth | | #4


    I only know of standing seam roofing installed in contact with the roof sheathing/underpayment. Can you explain what you mean by air gap? If the metal panels are not supported by the deck I’d think they’d get bent to hell if ever stepped/walked on.

    Sorry I can’t help with your actual question.


  5. Expert Member
    Akos | | #5

    There is a house in my neighborhood with nothing but GAF underlayment over the front porch for the past 5 years. Still holding up.

    I'm just doing a project with HAL breathX which is another option if available.

  6. Jon_R | | #6

    IMO, more people should build roofs that meet unvented specs and can dry outward. Similar for walls.

    1. Expert Member
      MALCOLM TAYLOR | | #7


      I agree. That's a great strategy for long-term resilience.

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