Frontage Increases

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6 comments

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    Stephanie Waples

    Hi Mark,

    I wondered the same thing about that particular question. It looks like it was a Ballast typo and they fixed it in the second printing. Their errata page says this:

    "The value in the 2nd printing as this erratum refers to is 20 feet. It was incorrectly given as 24 feet in the first printing and was corrected for the 2nd printing."

    Translated: the question should read that the open space is 20 ft wide. So, you're right -- that question as written should use 24 as the W. 

    Stephanie

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    Mark Diethelm

    Thanks! I thought I was going crazy.

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    Asra Zaidi

    I encountered a similar problem while studying Chings Building Codes Illustrated. the value of W is used 40 in the first example while 50 on the other, but i don't understand why they did not use the weighted average formula instead?  W = (L1 X w1 + L2 x w2 + L3 x w3 + ...)/F. can anyone help?

  • Avatar
    Mark Diethelm

    Asra,

    This is a clip from the IBC 2015 Chapter 5

    When the number for W is over 30' you would use the 30/30 as it's value, which would basically cancel out as 30/30 is 1.

  • Avatar
    Asra Zaidi

    Thank You Mark,

    what i don't understand is that why are they using 40 and 50 feet in place of W. I guess beyond 30' it doesn't matter but still, it is so confusing and annoying at the same time. 

  • Avatar
    Jonathan Chertok (Edited )

    i've always found Asra's questions and answers to be spot on. so i took note of this when i first reviewed the thread.

    not sure if her question will be tested but i also find this issue in Building Construction Illustrated to be confusing. tried to track it down through 2012 and 2010 version and it seems to me that there may be some typos here?

    anyway, started a thread to try and resolve it since at the very least it would be nice to know even if it is not a test item in ARE.

    https://are5community.ncarb.org/hc/en-us/community/posts/360008292033-2012-frontage-increases-what-when-and-ching-errors-506-2-and-506-2-1-?page=1#community_comment_360001013854

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