PA - Building Design and Environment

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    Michelle NCARB

    Hi Richard,

    Great question!  Big picture, PA is all about evaluating the requirements, constraints, and opportunities of a project. The initial study of site conditions in Section 1 starts to touch on how those conditions might work with the building program.  You're not yet designing the interior environment, but you're considering how characteristics of the site might inform that design.  It's about thinking ahead - given the building program, how could we take advantage of sun exposure, views, or topography, and what decisions can we make early on to get that ball rolling?

    Sample Item 1 is a great example of this, looking at how initial site selection can ultimately impact occupant comfort.  Does that make sense?

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    Richard Wilson

    Thanks Michelle! Very helpful.

     

    I have another related question, but regarding building form:

    Some resource materials state that the smaller the footprint the better (regardless of how tall the building gets). While other resource material cite more compact enclosures to be the way to go (such as a cube).

    As we study for the ARE 5.0 PA, is there a direction we should focus our studies, given the above two options? Or perhaps is there a single resource that NCARB would suggest to resolve these differences of opinion?

     

    I love skyscrapers. However, I personally believe, through my own investigations, that a compact building form (such as a cube) would be the most efficient. So I want to be sure to study the right material so that I have a good understanding of one choice over the other in my career.

    Thanks!

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    Daniel Spilman

    Hi Richard,

    I would say that in regards to the exam's direction, and architectural practice in general, that the building applicable building footprint is a factor of the site, environmental, and climatic conditions. Think about best practices / vernacular studies where footprints would vary if you have say, a hot desert climate vs. a cold snowy climate. This is exam has less to do with formal architectural studies in terms of aesthetics, but is very driven by how the surrounding conditions impact the design approach. 

    There are lots of resources out there that help to define these best practices, several of which are probably sitting on your self from your first couple years in architecture school! 

    Hope this helps. Best of luck!

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    Richard Wilson

    Hey NCARB,

    Regarding FAR:

    As I've been studying for the PA exam, I'm finding conflicting information on how to calculate FAR. In some instances, the number of floors is used in the calculations to determine tallest possible building, not taking the height of the roof into account. In other cases, I see that the roof is accounted for by adding roughly 14ft or so. In studying for this exam, will we need to be able to roughly guess the height from the top floor of a building to its roof level to accommodate for max building height? Or are FAR calcs including the roof level as a floor?

    Thanks!

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    Kevin Griendling (Edited )

    Hi Richard,

    FAR and Building height are separate but codependent elements in building design. They are separate because FAR is a planning department (local jurisdiction) regulation, not a building code regulation. Building height on the other hand is regulated by the building code (measured in stories), and may also have a more stringent requirement at the planning/local level (measured in feet). You must always follow the most stringent requirement.

    FAR is calculated by a square footage ratio of the site area, to allowable building square footage. Within that square footage you can mass the building however you want, with a small footprint building that is tall, or a wide footprint building that is low. In my PA course (due to publish late May), the example I use is a 10,800 square foot site with a building footprint on all floors of 4,000 sf. The question is 'How many stories can you build with an FAR of 1.3?'

    An FAR of 1.3 on a 10,800 sf site means you can build 10,800 * 1.3 = 14,040 sf

    As long as the building stays at 4,000 sf per floor you can build 3 stories. If your floor to floor is 12' and your maximum building height is 50', you will be 36' tall which is acceptable. The zoning code will actually allow you to build a 4th floor, but it would only be allowed to be 2,040 sf.

    1st floor: 4,000 sf - 0'-12'

    2nd floor: 4,000 sf - 12'-24'

    3rd floor: 4,000 sf - 24'-36'

    4th floor: 2,040 sf - 36'-48'

    Total: 14,040 sf

    Everything calculated above is a local jurisdiction requirement, not the building code. You will have to use Table 503 in IBC to make sure you are able to build that much for your specific occupancy.

    The 50' limitation in this example is to the top of parapet/ridge, so if it is a parapet building it would only be allowed to have a 2' parapet which is rather small. Mechanical equipment above the height limitation is different in every jurisdiction. Some allow it, some do not.

    Hope this helps. The images below consider the assumption that the client wants/needs to only build 4,000 sf straight up and is solely concerned with FAR calculation, not building height. But it is close to what you need.

     


    Enjoy!

    Kevin Griendling, AIA

    www.pluralsight.com

    www.paramarch.com

     

    (edited to add signature)

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    Michelle NCARB

    Hi Richard,

    This is a great write-up from Kevin!  I agree with his points, and I also want to answer your first question: no, you shouldn't just guess the height of a building.  You'll provided with the info you need to answer any question.

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    Cullen Hollyn Taub

    Kevin,

    I am confused by your statement on max building height to top of parapet or ridge. 

    Chapter 5 of the IBC states that building height is the vertical distance from the grade plane to the average height of the highest roof surface. Therefore, the ridge isn't the max building height, but the average height of the ridge is. 

    Also, per your statement, you are considering the top of parapet to be the highest roof surface. I would not consider a parapet to be a roof surface because typically, its main purpose is to screen mechanical equipment, provide fall protection or provide the minimum 8" turn up for roofing. And sometimes just to provide additional height to a building to fit in with its existing surroundings even though the program of the building doesn't require it.

    NCARB, can you confirm if we should consider the tops of parapets the highest roof surface or the top of roof framing? So far in my practice of architecture, I have not used the average method of stating roof height because I have always had room to spare. So when submitting to the AHJ I just state to top of ridge or parapet. For the exam, I will be using the average rule to determine both grade plane and building height as it is more accurate but would like to know where parapets stand. 

    Thanks!

  • Avatar
    Michelle NCARB

    Hi Cullen,

    I'll repeat what I said in my previous response - in any specific question, you'll be provided the necessary information to make a determination.  And I agree with Kevin's earlier distinction between zoning regulations and building codes, and the need to satisfy both sets of requirements.

    Your example from IBC is a good one, and it's pretty clear.  But zoning regulations vary from one jurisdiction to another.  The zoning ordinance in the demo exam, for instance, also specifies the average height of the highest roof surface.  But here in DC, zoning specifies that building height is typically measured to the highest point of the roof or parapet.

    Bottom line, if a question on the ARE asks you to calculate the building height, sufficient information will be provided so you won't have to guess at which way to calculate it. 

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