maximum allowable area of a building



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    David Kaplan


    It's a bit misleading to say that it's a "combination" of zoning and building codes.  That makes it sound like you could calculate the biggest building from a zoning perspective, then calculate the biggest building from a building code perspective, and then add the two together.  No way.

    What is intended behind that is that you have to do both of those processes to determine the maximum allowable area of a building.  With respect to the Zoning Code, you look at your site footprint and property line locations and then reference the setback requirements and/or FAR requirements outlined in the Zoning Code.  Using those requirements, you can find out how big of a building the Zoning Code will allow you to build on that site, but that is only the first step.

    From a building code perspective, you have to take into account the Use Group of the building, the proposed Construction Type, and whether or not the building will be sprinklered and/or have open perimeter frontage (the latter two categories allowing you SF increases per floor).  When you have all that information, you then use the tables in Chapter 5 of the building code to determine how big your building can be.

    Once you have the Zoning number and the Building Code number, you compare the two.  The strictest will win out. 

    I will say that on the ARE, at least in my experience, questions that required you to do these types of calculations did not ask you to do them BOTH for a single question.  As an example, you may be asking to calculate just the zoning footprint and not take into account building code.  Or vice versa.  You will be clearly told this on the exam.  Perhaps you could be told to do both for one question - I'd be surprised because that'd be very time-consuming, but I suppose you never know. 

    You should know how to do both calculations though.  Hope this helps!

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    Carolina Quintero Duque

    Thanks for the clarification. I was a bit confused. How this will work for existing bldgs?

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    David Kaplan


    If it's an existing building, the square footage really doesn't come into too much play.  It if it doesn't meet the setback requirements set in the zoning code, or perhaps is taller than allowed in the Zoning Code - well, hey, the building is sitting there.  It is what it is.  Most cities would say in that instance that it's grandfathered in.  However, they may require that you obtain a variance if you are seeking to do an addition to the building that would make an already non-compliant-but-grandfathered situation even worse.  This is pretty common.

    With respect to the Building Code height/area limits - again, if it's existing, it's grandfathered in.  However the one hang-up you can experience is if you're doing a Change of Use.  If you're keeping the building that doesn't comply with the height and area limits for its current use as it is, and you're changing it's Use Group entirely (like, converting an old department store into apartments say), you have to analyze the building's SF against the new Use Group.  This may involve you having to compartmentalize the building either into fire areas or installing new fire walls.  I had to do this on a job that converted an old factory complex into one big Assembly Use. 

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