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Common wall above roofing

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  • Common wall above roofing


    The plan is to strip an existing built up roof and insulate with rigid foam boards but there's a possible issue.

    6" of board is needed but the common wall between this property and the adjacent rowhouses juts only 3" above the roof deck.
    I can build a curb to provide a solid edge for the insulation but will having all of that 3" above that common wall an issue?

    Why does the common wall rise above all rowhouse roofs? (Philadelphia)
    Fire prevention, to direct water to each owner's scupper and down spout?
    Would rising above that wall create a code violation?

    It would be great if I could reach a human at the City's code office but they are overwhelmed.

  • #2
    Re: Common wall above roofing

    Firecode. Rated property line walls must meet fire rated roof structure or extend above the roof plane. 30", not 3" is what I'm used to, though. Philly may have a local variation on the theme.

    AND you need to know if the roof-ceiling assembly is fire-rated. You can't add a bunch of insulation to an assembly without affecting the fire rating