Leasable area



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    Stephen Starks



    The way this question seems to work is:

    1. We are given a target "Net" SF to meet / calculate for = 4500 SF.
    2. We are informed that the the target existing office building's "Efficiency" = 0.75
    3. We are informed that the building load factor = 1.20.

    If the building was 100% efficient (1.00) we could multiply Net SF by building load factor and be done - but the target building does not use available space as well as that, and this must be accounted for by an additional step.

    From "target Net" and "existing Efficiency" we then determine that the building's actual "Gross" SF = 6000 SF.

    We then multiply 6000 SF by 1.20 and the product = 7200 SF (Answer C).

    Alternately: (4500 SF / 0.75) x 1.2 = 7200 SF. (this method is a bit less cumbersome).


    As always, check up on this your self though.

    Thanks for the exercise :)

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    Shanglin Li

    Thanks Stephen,

    but I still couldn’t understand this, cuz first, I understand this loading formula is relative to Rentable and Usable space, there’s nothing about Gross area. Second, bases on the answer, is that means the Rentable Area is larger than Gross area? How is that possible?


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    Francis Pham

    Hi All,

    Was anyone able to follow up on this? I also dont understand this as R/U = rentable/useable , Gross area is not mentioned anywhere. So why solve for gross area ? 

    Thanks ahead of time!

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    Alexis Church

    In this example - Gross comes into play by definition of Building Efficiency.

    Net / Gross = Efficiency.  Note that Net excludes circulation, service areas, etc.

    4500 sf / 6000 sf = .75

    In this example, Gross is more related to Usable Area because Ballast is referring to the Gross Area of 1 tenant, not Gross Area of the entire building.  This area may include circulation or service areas specific to this tenant.

    So Usable Area includes all space given to this 1 tenant (aka Gross in this example) x 1.2 Building Load.  The Building Load accounts for shared spaces such as lobbies, reception, restrooms, primary circulation, etc.  This is shared among all tenants and is usually proportional to the tenant's Usable Area.  Thus resulting in the 7200 sf which is the amount the tenant will pay rent for.

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    Yanli Xiong


    This has been a bit confusing for me also.

    For the calculation of efficiency, the book mentions circulation and mechanical rooms, as examples of nonassignable areas.

    For the calculation of load factor, the books lists corridors and mechanical rooms, among other things, as shared spaces.

    It's a bit confusing since it seems like there may be some overlap between the two calculations. Should I assume there is no chance of overlap since it would be in the owner's best interest to minimize the load factor?

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