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  1. #1
    Join Date
    Mar 2007
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    Ormond Beach, Florida
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    25,317

    Default roof slope vs roof pitch

    I know we started to discuss this once, then got side tracked, but ...

    I was just looking through a 1939 4 volume set of Audels Carpenters & Builders Guide (only the 'Old Farts' here will remember those things) and came across the 'roof slope vs roof pitch' chart.

    slope - pitch
    2/12 - 1/12
    4/12 - 1/6
    6/12 - 1/4
    8/12 - 1/3
    10/12 - 5/12
    12/12 - 1/2
    14/12 - 7/12
    16/12 - 2/3
    18/12 - 3/4
    20/12 - 5/6
    22/12 - 11/12
    24/12 - 1

    You will notice that "pitch" is based on rise versus 2run.

    With run = 12, that means "pitch" is rise vs 2run or 24

    6/12 slope = 6/24 pitch = 1/4 pitch

    This was based on the assumption that the roof started at the wall, rose to the ridge, then went back down to the other wall (2 runs for 1 rise).

    If the roof rose 6 feet to the ridge, the ridge was 12 feet from the wall, then went back down 6 feet to the other wall 12 feet further, you had a rise of 6 feet over a run of 24 feet, or 6/24, reduced to the lowest common denominator = 1/4.

    Remember, early buildings had roofs which were simple triangular structures, gable on one end, gable on the other, roof the same from gable to gable. Symmetry was the simplest and strongest way to build a roof.

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  2. #2
    Daniel Stone's Avatar
    Daniel Stone Guest

    Default Re: roof slope vs roof pitch

    Hey Jerry...I have a complete set of 4 books that my father gave me...never could have framed without them.!


  3. #3
    Daniel Stone's Avatar
    Daniel Stone Guest

    Default Re: roof slope vs roof pitch




  4. #4
    Join Date
    Mar 2007
    Location
    Ormond Beach, Florida
    Posts
    25,317

    Default Re: roof slope vs roof pitch

    Daniel,

    In COLOR too!

    What year?

    I got mine from my Dad too.

    I've also got a 1951 4 volume set from him too. Alas, though, it also is still only the old black cover/binding.

    Along with several old American Electricians Handbooks, from the 1940s and 1950s.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
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  5. #5
    Join Date
    Mar 2007
    Location
    Healdsburg, CA
    Posts
    1,741

    Default Re: roof slope vs roof pitch

    Carpenter's square is all you need. Mine (cica 1950) and the common pitch de jour in the San Francisco bay area tract homes (mostly ranch style) during the 50s, 60, and 70s was 4-1/2 & 12. Personally I liked either a 5 or 6 & 12 pitch.

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