This is the third essay in a trilogy. The first two
were entitled “The Future of Cities” and “Understanding a Building Footprint”.
NOTE: All tables referenced are located after the text
When parking is required, core area is the buildable land
area remaining for shelter and parking after a number of support areas are
subtracted from gross land area. Shelter capacity is affected by the building
design category chosen, the core land area available, and the building height contemplated.
This essay is based on a G1 Design Category that depends on surface parking and
building footprint areas that combine to equal the total core land area available.
The emphasis here is on available quantity. It has nothing to do with preliminary or final
site plan configuration. This definition of core area makes the formation of
shelter capacity equations feasible.
In some cases an architect will know the gross land area
available and the objective will be to calculate its gross building area
potential - Case 1. (I’ve covered Case 1 in two previous essays entitled, “The
Future of Cities” and “Understanding a Building Footprint”.) In other cases the
architect will know the gross building area desired and the objective will be to
calculate the buildable land area required - Case 2. In some cases the
gross land area available and the gross building area objective is known, but
this essay is based on Case 2. The answer in both cases depends on the core
land area remaining. In Case 2 it is an unknown to be discovered.
Table 1 is related to Case 1. It illustrates the subtraction
that leads to the definition of core area in cell F32 and G32 based on the gross
land area given in cell F3. (The percentage estimates and calculations in cells
F3-F31 lead to the core area estimation in cell F32.)
Table 2 is related to Case 2 and does not begin with a given
gross land area. It illustrates the distillation of core area in cell F32 based
on the percentage estimates and calculations in cells F3-F31. No square foot
land areas are given or calculated.
I introduced the G1 Building Design Category and its Case 1 master
equation entitled G1.L1 in “The Future of Cities”.
GBA = CORE * af / (a + (fs))
KEY:
a – gross building area square feet permitted per parking
space provided
CORE – buildable land area available for building
and parking cover in square feet
f – floor quantity
GBA – gross building area potential in square
feet
s – gross parking lot area provided per
parking space provided in square feet
The equation solves for an unknown gross building area (GBA)
when land area is given, but can be transposed to solve for the core land area
needed when a gross building area objective is given:
1)
CORE = GBA / af / (a + (fs)) Transposing
master equation G1.L1
2)
CORE = GBA / (a2f + af2s) Reducing line 1
3)
CORE = GBA / (af * (a + fs)) Reducing line 2
Defining core land area is not the answer to the question
posed, however. It is the first step in the derivation:
4)
CORE = CORE% * SHA When shelter area (SHA) in sq. ft. is known
5)
SHA = SHA% * BLA
When buildable land area
in sq. ft. is known
6)
CORE = CORE% * SHA% * BLA Substituting line 5 for SHA in line 4
7)
CORE = GBA / (af * (a + fs)) Repeat line 3
8)
GBA * ((a + (fs)) / af) = CORE% * SHA% * BLA Substituting line 7 for CORE in line 6
9)
GBA * (a +(fs)) = CORE% * SHA% * BLA * (af) Reducing line 8
10)
BLA =
(GBA * (a + (fs))) / (CORE% * SHA% * (af))
Transposing line 8 to
find Equation G1.B1.BLA
Equation G1.B1.BLA on line 10 is located in cell A38 of
Table 2. It is used to calculate the buildable land area options in cells
B43-B52 of the table. At this point, the equations in cells C42-L42 are used to
calculate additional option columns related to the floor quantity options in
cells A43-A52. Shelter capacity, intensity, intrusion, and dominance measurements
related to each option are calculated in Columns G-L of the Planning Forecast
Panel.
I should again point out that floor quantity above 5
produces rapidly declining gains in gross building area per floor when the G1
Design Category is chosen for shelter construction. This was discussed in “The
Future of Cities”.
The buildable land area in cell F9 of Table 2 is estimated
to be 82% of the gross land area needed (GLA). An estimate of this gross land
area can be simply expressed as:
GLA
= BLA / BLA%
In other words, a GLA estimate can be defined with the
following revision to Equation G1.B1.BLA
GLA
= (GBA * (a + (fs))) / (CORE% * SHA% * BLA% * (af)) Master Equation G1.B1
Master Equation G1.B1 is one of 25 related to the building
design categories listed in Table 3 and presented in my book, The Science of
City Design, CreateSpace, 2016. The derivation of Equation G1.B1.BLA can be
found on page 154, lines 62-67. The book, and the second edition of my earlier
book entitled Land Development Calculations, can be found on Amazon.com
at the following address:
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