frontage increase



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    Brett Spencer

    I'll start off by saying that I do not think you'll need to worry about frontage increase for P&A -- it's more for PPD and even PDD.  But with that being said, the concept itself is much easier than the actual equation that is involved.

    Frontage increase is essentially a factor in the allowable area of a building.  The more area you have between your building and it's property line (for public access use, fire lanes, etc.) the larger of an allowable area to your building you may have.  The equation for allowable area is determined by Section 506.2.3 of the IBC and is a good section to be familiar with.  It is as follows:

    Aa = {At + (NS * If} * Sa; where

    Aa = allowable area

    At = Tabular area factor (found in code)

    NS = Tabular area factor w/out sprinklers (regardless of whether or not sprinklers are present)

    If = increase due to frontage (will be a number between 0 - 1)

    Sa = actual number of stories (max of 4)


    The equation for the frontage factor is as follows:

    If = [(F/P) - 0.25) * W / 30; where

    F = building perimeter that fronts on a public way or open space having 20'-0" min. open width

    P = perimeter of entire building

    W = width of public way or open space in accordance with Section 506.2.1


    I would certainly read section 506.2 of the IBC for further clarification since it is not an easy concept to grasp and the equation itself is tedious and takes a little work. But I hope this is at least a start to trying to understand it.  Again, I don't think it is something you will come across in P&A, or at least it wasn't something I was introduced to until studying for PPD.

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    Oluwasesan Aduroja

    Ok thanks

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    Benjamin Norkin

    Oluwasesan, I go over the entire equation here:

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