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Community and Q&A

Roof underlayment

Quinton Bryant | Posted in Energy Efficiency and Durability on

Building in zone 3,cathedral ceeling in 3rd floor bonus room,using 3.5 inches of OCF and 3.5 inches of cheaper in trusses,than using a john mansville nailbase,we will have first layer of 7/16 osb roof sheathing than put nailbase down,what kind of underlayment would you advise to go on top of nailbase and under standing seam room.

Also what is the most cost effective window flashing,zip,tyvek straight flash etc.

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  1. Quinton Bryant | | #1


  2. Joe Suhrada | | #2

    Synthetic underlayment. Also, use 5/8" OSB so you avoid clips. Clips make make bumps visible if you use a darker colored roof. Also, what is your pitch?

  3. Quinton Bryant | | #3

    12/12 pitch
    I will have 7/16 osb than 1.5 inch polyiso that's bonded to another layer of 7/16 osb,no were to put clips.

  4. Quinton Bryant | | #4

    Unless they need to go on bottom layer of osb for support?

  5. Joe Suhrada | | #5

    The ones underneath the foam don't matter. 12/12 you can use a snap lock panel roof no issues. That is one hell of a steep roof.

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