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Wednesday, October 10, 2012

The Influence of Design Decisions

Twentieth century architecture pointed to our symbiotic imperative with two famous phrases: “form follows function” and “organic architecture”. They both meant that a flower grows from its roots in the land and blooms when in harmony with a universe of forces beyond its comprehension, in my opinion. Architecture has roots in the land, but only symbiotic human decisions can make it bloom in harmony with the planet's sovereign power.

Five decisions determine the development capacity of land to shelter activity when surface parking is the preferred storage solution. Architects often take these decisions for granted because they learn to evaluate options and make decisions intuitively; but this impedes the accumulation of knowledge since it depends on talent that cannot be taught. It can only be improved.

These decisions involve five primary variables that affect gross building area GBA potential on a given buildable land area BLA when surface parking around, but not under, the building is contemplated (G1 design category).

I’ll explain these topics by beginning with an equation derived in “Replacing Density”. It stated that:

GBA = f*(CORE) / (1+ (fs/a))
f = Number of building floors
CORE = BLA – (S+M)
BLA = Buildable land area in sq. ft.
S= Project open space as a % of BLA
M = Misc. pavement as % of BLA that includes loading area & pavement beyond parking lot area
s = Average area per parking space in sq. ft., including landscaping, within the parking lot perimeter
a = GBA sq. ft. permitted per parking space provided
This can be reduced to a universal equation with five variables when the equation is unwrapped.
Given: GBA = f*(CORE) / (1+ (fs/a))
GBA*(1+ (fs/a)) = f*(CORE)
Since CORE = BLA-(S+M)
GBA*(1+ (fs/a)) = f*(BLA-(S+M))
GBA = (f*(BLA-(S+M))) / (1+ (fs/a))
When BLA=1,
Equation (1):  GBA = (f*(1-(S+M)) / (1+ (fs/a))   
NOTE: GBA is expressed as a fraction of BLA

The five variables in Equation (1) are (f), S, M, (s), and (a) and the values assigned represent shelter design decisions that set the stage for all decisions that follow. The values (f) and (a) are generally specified in a zoning ordinance, but the values S, M, and (s) are often overlooked. They are critical to successful leadership, however; and their omission is the easiest way to explain why zoning has been able to separate incompatible land uses but unable to avoid over-development and sprawl. Any regulation that omits one or more of these five elements for the G1 design category simply encourages arbitrary debate over isolated detail. Equation (1) shows that all five are needed in the equation and that results are produced by their interaction. The next five tables are examples of this interaction.

Table 1 illustrates the GBA options produced by Equation (1) when project open space S is a variable along the x-axis; building height is a variable along the y-axis; and the values (a), (s), and M are held constant. GBA options are expressed as percentages of BLA and the option range is stated as a percentage of BLA in the upper right hand corner of the table. In this case, the range is 30.1% and begins with GBA=1.4% BLA when (f) =1 and S=90%. Some of these options are undesirable, but research is still not available to support intuition with knowledge.

Tables 2-4 repeat the exercise with different variables along the x-axis. Table 2 illustrates GBA options when the average parking lot area provided per parking space (s) varies. The GBA range noted is 14.2% and begins with GBA=1.15% when (f) =1 and (s) =900 sq. ft. of total parking lot area per parking space.

Table 3 illustrates GBA options when the parking space requirement per thousand sq. ft. of GBA (alt-a) varies along the x-axis. The GBA range noted is 192.4% of BLA and begins with GBA=7.6% when (f) =1 and (alt-a) =20 parking spaces required per thousand sq. ft. of GBA.

Table 4 illustrates GBA options when the miscellaneous pavement percentage M varies along the x-axis. The GBA range noted is 12.3% of BLA and begins with GBA=12.9% when (f) =1 and M=25% BLA.

Table 5 is the primary battlefield of zoning. It presents GBA options when project open space S varies along the x-axis and parking requirements (a) vary along the y-axis. The number of building floors is constant at f=5 for this example. The greatest development capacity potential GBA can be found in the S.1, or 10% open space, column. This GBA capacity can be increased further by requesting a variance to the parking requirement (a) that applies. For instance, a variance from 5 to 4 parking spaces per thousand sq. ft. of GBA would produce a 9% increase in GBA potential in the S.1 column.

The ten percent open space in Table 5 is not desirable, nor is 375 sq. ft. of parking lot area per space, and a parking requirement of 4 spaces per thousand is not enough to support some land use activities. I make this point because I’m not trying to advocate individual design specification values. I’m trying to explain how they interact. When one or more is omitted it is impossible to accurately predict development capacity with Equation (1); and I have already pointed out that three are often overlooked in zoning ordinances and the other two are considered independently. In other words, it is impossible to plan and lead shelter for growing populations within sustainable geographic limits when these equations are not understood. This in turn makes it impossible to protect the Natural Domain from sprawl and the Built Domain from excessive intensity because special interest arguments often trump public uncertainty.

At the present time my guess is that most zoning ordinances do not regulate project open space S, miscellaneous pavement M, and/or minimum parking lot area per space (s). Even if they did, their requirements in isolation can be contradictory when not correlated.

In addition, zoning requirements are rarely based on a land use plan with self-imposed geographic limits; or a massing plan for the urban form of shelter that is correlated with its physical, social, psychological, environmental, and economic implications. In other words, city planning has separated incompatible land use activities, but it has done it with sprawl that threatens our source of life.

Architects take the five variables in Equation (1) for granted. They use intuition to correlate these elements with design sketches. He or she cannot complete a project without considering these five variables; but the graphic methods of solution have limited the options that could be evaluated, and their mathematical foundation has been overlooked by an emphasis on “talent”. This has limited the accumulation of knowledge.

Table 6 summarizes the results in Tables 1 -5, but these results only illustrate how Equation (1) works. They do not represent recommendations. All results are expressed as a multiple of the buildable land area BLA available.
It should be fairly obvious from the results that building height (f) influences development capacity GBA, but that the surface parking requirement (a) is the most influential. A closer look at Table 3 will explain this more fully. If you look at the (f-1) row, the development capacity GBA varies from 7.6% to 40% of BLA depending on the parking requirement (a). This is a range of 32.4%. The two-story range is 64.7%. The five-story range is 161.8%. All of these ranges are a function of a variable parking requirement (a) within a constant building height (f) row, and they all exceed the development capacity ranges available in the other tables. In other words, modifying the value (a) has the greatest potential to increase development capacity GBA for the G1 design category. It’s not hard to understand the number of variance requests from parking requirements (a) when looking at the potential GBA range in Table 6, but keep all of the tables in mind. It is not only (a) that influences development capacity, and design leadership must have all five reins under control to prevent a run-away.

Design begins with the correlation of relationships in Equation (1). This defines the context format for architecture and city design when the G1 design category is considered. Buildings emerge from a context format and symbolize our progress toward shelter for growing populations within symbiotic limits that do not threaten our source and quality of life.

Intensity and over-development become a problem because project open space S, miscellaneous pavement M, and minimum parking lot area per parking space (s) are rarely specified or correlated in zoning ordinances. The omission inadvertently emphasizes building mass and pavement. The public is compressed in a right-of-way of increasing traffic and pollution. Storm sewer capacity is threatened by excessive impervious cover, and the list goes on. The battle is often fought within Tables 1-5 when surface parking is involved, and many real estate investors / building owners / speculators would prefer choices in the left-hand column of each, but this is a recipe for excessive intensity that will not protect our quality of life.

Architects will have a lot to offer when they decide to quantify intuition, demand context, and accumulate knowledge to defend design decisions that benefit the public interest.


In the end it’s all about gross building area GBA potential on a given buildable land area BLA because GBA can be used to shelter any activity. For instance, if you divide the gross area of an existing apartment building by the number of dwelling units present the result will be an average gross dwelling unit area ADU statistic. If you divide the GBA forecast for another buildable land area by the same ADU, its dwelling unit capacity can be predicted, assuming the same dwelling unit mix and areas. The critical piece of information is the development capacity GBA of land, and it can be forecast.

Single family homes are no different. Gross building area shelters a specific activity on a given land area. The GBA capacity of a residential lot is a function of the five variables in Equation (1). Gross building area is the universal currency. It is simply tailored to meet the needs of a specific activity. I’ll have more to say about this in the future.

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