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Low-slope roof Climate Zone 6

brandons | Posted in General Questions on

Climate zone 6 entertaining roof options.  Any concerns with performance or compliance of this assembly?

5/8″ Gypsum Board
3.5″ service cavity (with fiberglass R-13 Batts)
Intello membrane
14″ TJI sloped to 3/8:12 (with blown in fiber glass R-53)
1/2″ Advantech
Henry VP100 self adhered membrane
2 layers 3/4″ furring strips (one layer vertical, one horizontal)
1/2″ Advantech **
Peel and Stick roof membrane

For the wall assembly I decided on 3/4″ rainscreen, Henry VP100 self adhered membrane, 1/2″ Advantech, 2×6-2×4 double stud with blown in fiberglass R38, Intello membrane, 1/2″ Gypsum board

If the roof works the idea is tying the wall/roof membranes together similar to the “Perfect Wall House”

**I considered Densdeck but don’t know if it can be installed over furring strips or requires a solid underlayment.

I searched section 9 in the IRC but couldn’t find specifics.  If I omit overhangs on the roof, is a parapet required?


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  1. GBA Editor
    Martin Holladay | | #1

    No, that won't work. You can't vent a low-slope roof with this approach, because there will be no air flow through the ventilation cavity (even if you have soffit vents and a ridge vent -- and you didn't mention whether you were considering having those).

    The only way to have a safe vented assembly with a low-slope roof is to follow the recommendations in this article: "Insulating Low-Slope Residential Roofs."

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