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Community and Q&A

Drying on flash and batt unvented concrete tile roof – CZ3

Rob Hunter | Posted in Energy Efficiency and Durability on

Didn’t want to hijack the standing seam metal roof question, but I would like to confirm the details needed for my flat concrete tile roof in CZ3 (California)

Parallel chord web trusses, 5/8″ plywood with 2″ of closed cell foam (balance of insulation will be blown in cellulose or blown in fiberglas). Boral standard weight tile.

Is this a case where, as Martin said in the standing seam thread, the sheathing doesn’t have/doesn’t need a drying path – if so, should i use a vapor-impermeable underlayment? Goal is to end up with a roof that isn’t vulnerable to ember-driven fires… and, of course, keeps the weather out 🙂

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Replies

  1. Rob Hunter | | #1

    Oops - the tile is flat, not the roof. Pitch is 6/12. Sorry!

  2. GBA Editor
    Martin Holladay | | #2

    Rob,
    Concrete roofing tiles are vapor-permeable, so this type of roof assembly can easily dry to the exterior.

    The best type of roofing underlayment for this type of roof is a vapor-permeable synthetic underlayment like Perma R Products PermaFelt, GAF Materials Deck-Armor, Cosella-Dörken Delta-Maxx Titan, VaproShield SlopeShield, Cosella-Dörken Vent-S, Nemco Industries RoofAquaGuard BREA, or Cosella-Dörken Delta-Foxx.

  3. Rob Hunter | | #3

    heh - that makes it easy! Thx for clarifying, another detail off my checklist.

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