Cities and Design: Taking the Pulse of Architecture

There is a simple truth in architecture. Building mass and pavement are offset by project open space to produce levels of project intensity. These projects accumulate to become the Shelter Division of the Built Environment. When “over-development” occurs, parking lots and the right-of-way become surrogates for open space. Public reaction to this hostile environment produces escape by “sprawl”. Navigating this Scylla and Charybdis of intensity will require more than a choice between two tragedies -- but the dead reckoning of politics, real estate law, planning regulation, and development construction is not equal to the challenge. These efforts seek to influence architectural decisions without understanding its interactive response to independent requirements. It’s like prescribing medicine without understanding its side effects.

The pressure within cities is called “intensity”. Like blood pressure, it can be an indication of sickness or health. High and low blood pressure is caused by political assumptions and design specification values that represent city design decisions. Fortunately, it is possible to accurately measure the pressure of intensity by recording design specification values that determine its mass and context. This makes it possible to observe, index and evaluate the conditions created. These conditions represent the architecture of city design. The challenge is to lead it toward symbiotic compositions based on the knowledge acquired.

Design specification values interact to produce development capacity options. These options can be predicted with forecast models. Development capacity is gross building area GBA. I’ve used it as a surrogate for building mass in these models because floor area can be used to predict many related implications. When talking about Development Capacity Evaluation software DCE, therefore, mass and capacity are synonymous terms.

Building mass and pavement is offset by project open space to produce levels of intensity, and intensity is a term defined with design specification values that have leadership potential. I’ve attempted to summarize these values with an index of intensity in the forecast models mentioned, but have not been happy with the results. These indices have taken the form (f.S) and (GBA / BLAC). In the first, (S) is the percentage of buildable land area provided as project open space and (f) is the number of floors present, planned or permitted. Unfortunately, (f) is an inadequate description of mass and open space S reports quantity with little indication of context that changes with mass and height. In the second, intensity is predicted as the gross building area in square feet per buildable acre available. It is a definition of mass and intensity that leaves context to the imagination and may be too detailed for leadership application.

Ideally, an intensity index would indicate the massing, intensity, and context present, planned or predicted. This has led me to search for another option, but first I’d like to explain some terms for first-time readers.

Definitions

Figure 1 illustrates terms such as gross land area GLA, net land area NLA, unbuildable land area UNB, buildable land area BLA, and core land area CORE. Unbuildable areas include, but are not limited to, excessive slopes, ponds, wetlands and unstable soil. They represent scenery that does not reduce the intensity of the buildable land area inhabited. They are excluded from intensity calculations because inclusion produces a lower intensity value that distorts the habitable conditions created. In other words, buildable land area is equal to net land area minus unbuildable area as shown in Figure 1. All intensity calculations are based on this logic to convey a better indication of the habitable conditions present, planned or predicted. In mathematical terms, BLA = NLA – UNB and buildable area is available for core area development and project open space BLA = S + CORE. The core area calculated is available for parking cover and building cover CORE = PCA + BCA. The percentage of open space S provided within the BLA offsets core area development and defines two-dimensional site plan balance.

Figure 1: Site Plan Naming Conventions

Building mass emerges from building cover within a core area. It combines with two-dimensional development cover and is offset by project open space S to create three-dimensional context within a buildable land area. (Think of mass as a glass volume that encompasses all detailed architectural form and appearance with a simple geometric shape. Architectural features are sculpted from the volume defined like a sculptor releasing form from a block of marble.) From a planning perspective, MASS = GBA = (BCA * f). A massing index indicates the relationship of building mass to buildable land area Mx = GBA / BLA. An intensity index indicates the relationship of building mass to project open space Ix = Mx / S, and context has an inverse relationship to building mass Cx = 1 / Mx. In the Cx equation, context begins with a project open space percentage allocation S that is part of the massing equation. The benefit from constant S declines as mass increases with height in the core area. This is more clearly explained in the derivation to follow.

Derivation

Given:

MASS = GBA

GBA = f * BCA

These are conventions adopted for architectural massing calculations when the sky-plane requirements for high-rise buildings are not a factor. Sky-planes will be addressed later.

When gross building area GBA in square feet is divided by the buildable land area BLA in square feet, the result is a massing index Mx that is a multiple of the BLA. It is similar to a floor area ratio FAR, but the divisor is based on buildable land area rather than total land area. This more accurately reflects the intensity created within a habitable land area.

Mx = GBA / BLA

Since GBA = f*BCA and BLA = CORE + S

Mx = ( f * BCA) / (CORE + S)

The values f and S are design specification values entered with others in the design specification template of a forecast model. (See Table 1) Building cover area BCA and core area CORE are calculated from these values, along with other fundamental design implications. A massing index Mx summarizes the gross building area GBA impact on the buildable land area occupied. It is expressed as a multiple of BLA and reflects the implications of all design specification values entered.

Architectural intensity is the relationship of building mass to project open space. An intensity index Ix can be created by dividing a massing index by the percentage of open space provided S at grade. The intensity value increases as massing increases since increasing mass exerts increased pressure on the constant open space allocation. This pressure is also expressed as a multiple of BLA.

Ix = Mx / S

Open space benefit drops when mass increases and open space remains constant. The result is context decline that has an inverse relationship to the mass introduced. The Cx index expresses this phenomenon as a multiple of BLA that declines as Mx and Ix multiples increase.

Cx = 1 / Mx

In other words, mass and intensity are functions of the values entered in a design specification template. Their index equations summarize the results with values that are multiples of the buildable land area BLA. Context declines as mass and intensity increase. This inverse relationship is defined by the Cx value that is also reported as a multiple of the buildable land area involved.

Discussion

Composition indices can be particularly helpful when attempting to document the decline in open space benefit produced by increasing building mass and height on the same property. For instance, the “Skyscraper” section of this essay shows how a 20% open space allocation can decline to a 1.4% percent benefit when adjacent to a 200 story building, and this doesn’t take present and future population and traffic into account.

Tables 1 -4 present some examples of massing, intensity and context indices produced by design specification values. Table 1 calculates these indices based on the values entered in the CG1L forecast model. This model represents buildings with grade parking lots around, but not under, the building in non-residential land use areas. Table 2 calculates massing, intensity and context indices for a residential apartment building using the forecast model RG1L. Table 3 calculates these indices for a single family zoning table. Table 4 calculates them for a high-rise building using a modified version of CG1L.

Massing, intensity and context indices summarize an architectural composition of mass, pavement and space. The summary pertains to the design category represented by the forecast model chosen. The values entered in its design specification template produce development capacity, or intensity, options summarized by these composition indices.

Tables 1–4 demonstrate how composition indices are forecast. They can also be measured at existing locations for comparison with their broader physical, social, psychological and economic implications; but we have not begun the process. This puts us at a level of awareness equal to those who first experimented with blood pressure. They lacked a diagnostic history, but began to record their readings and correlate the conditions observed. Architecture and city design can benefit from the example.

Mass and intensity can easily dominate public benefit, which has been referred to as its health, safety and welfare. When project open space at grade is zero private benefit is served by the building, but public benefit declines to a margin of sidewalk served by a modicum of light, air and ventilation in the public right-of-way. The right-of-way benefit is then reduced by growing populations and traffic attracted to the adjacent real estate investment. This is covered in more detail under “Right-of-Way”, but it points to a refined version of the simple truth mentioned earlier. Mass and intensity are offset by open space context. A paucity of context produces oppression while excess produces sprawl.

Examples

Table 1 presents a prediction of massing GBA options based on the forecast model CG1L and the values entered in its design specification template. Project open space is entered as 30% of the buildable land area. The design premise for this model is a grade parking lot surrounding, but not under, the building(s). A range of values for f is entered in its Planning Forecast Panel. Values for BLA, GBA, and BCA are calculated and presented in its forecast panel by the model’s embedded equations. Mx, Ix, and Cx results are calculated from these predictions in the last three columns. They can also be calculated for existing projects by taking field measurements for BLA, GBA, BCA, S and f.

The massing range Mx predicted in Table 1 for one to four story building options is 0.25 / 0.381 of the buildable land area BLA. The intensity range Ix is 0.833 / 1.171 times BLA and the context range Cx is 4 / 2.85 times BLA. The context values describe a decline from 4 / 2.85 as building mass and intensity increase with height. (Tables 1 – 4 are presented at the end of this essay to avoid interruption.) A context decline from 4 to 2.85 is not tragic, however. It indicates that the context benefit from a 30% open space specification is still 2.85 times BLA . The massing range from 0.25 to 0.381 times BLA is still a modest fraction. This indicates that the intensity increase from 0.833 to 1.171 times BLA is well within tolerable limits.

Table 2 is based on the same design premise and open space provision of 30%, but contains a different design specification template for apartment buildings. It indicates that the massing range for one to four story apartments is 0.43 / 0.84 times BLA. The intensity range is 1.2 / 2.8 times BLA and the context range is 2.35 / 1.19 times BLA. This shows a similar decline in context benefit from 2.35 to 1.19 as mass increases from 0.43 to 0.84 times BLA. Intensity also increases from 1.2 to 2.8 times BLA. All of these readings, however, indicate benign massing, intensity and context relationships.

In Table 3, buildable land area BLA is equal to the minimum lot size permitted per dwelling unit in each zone. It shows that a rather typical single family zoning ordinance permits a massing range of 0.15 / 0.625 BLA; an intensity range from 0.167 / 1.250 BLA and a context range from 6.667 / 1.60 BLA. The massing index range (0.15 to 0.625 BLA) indicates that gross building area is a fraction of the minimum lot area required in each zone. The low end of the intensity range (0.167 BLA) indicates that intensity is also a tiny fraction of BLA while the high end (1.25 BLA) indicates what is presently considered a rather small detached single-family residential lot. The high end of the context range (6.667 BLA) indicates that open space benefit is 6.66 times BLA for a 3 acre lot. The low end (1.60 BLA) indicates that project open space benefit remains greater than BLA for a 9,000 sq. ft. lot. This highlights the desirability of low density residential massing while also explaining the contribution of high context values to excessive sprawl.

Table 4 includes the unique characteristics of skyscraper sky-plane requirements. It is based on 20% open space and all other design specification values entered. A more detailed explanation will follow; but for now, Table 4 predicts that a 50 story skyscraper will produce a building mass equal to 31.6 times the buildable land area BLA, intensity equal to 158 times BLA, and context equal to 0.0316 times BLA. It also shows that a 100 story skyscraper will produce mass of 50.7 BLA, intensity of 254 BLA, and context of 0.0197 BLA. Common sense is again confirmed. The context range of (.0316 / .0197 BLA) declines as the massing range of (31.6 / 50.7 BLA) and the intensity range (158 / 254 BLA) increase.

As I mentioned, these readings are like blood pressure without medical research. They provide an accurate picture, but the physical, social, psychological and economic implications of these readings remain to be determined.

In summary, Tables 1-4 indicate that when design specification values remain constant; increasing building height increases mass and intensity while context benefit declines. These relationships are charted in Figure 2 based on Table 1 statistics.

Figure 2: Relation of Massing and Intensity to Context

City Design

Project context is inversely proportional to mass and intensity on a given buildable land area. This does not take street width, traffic type, traffic volume and surrounding intensity into account. These factors are controlled by the decisions of others, but they are part of the public issue I’ve referred to as city design. City design intensity is equal to the sum of its parts. Shelter intensity is one part that is equal to the sum of individual architectural projects. These have independent and collective social, psychological and economic implications. This may help to explain how architecture contributes to city design; why I’ve used the term “architecture of city design” in some essays; and how independent architectural decisions must be woven together with project open space contributions to avoid dissonance.

Rights-of-Way

Right-of-way width is the foundation for public context within the public domain. Many of these rights-of-way are consumed by traffic volume and supplied with minimum standards of light, air, and ventilation. In some cases these rights-of-way are more than one-hundred years old and growing populations have become compressed along narrow ribbons of sidewalk reduced by increasing traffic volume and degraded by its pollution. This brings the entire concept of dual-purpose rights-of-way into question -- if it ever existed as a balanced concept in the first place.

The public interest is again involved. The building mass, context and intensity created along these rights-of-way can trap populations in corridors too congested to serve their original purpose, let alone a combined purpose. We are all familiar with this road named Decline and it is a city design topic for another day. In simple terms however, we cannot afford the continued belief that hospitable cities are woven together with movement systems.This is a utilitarian point of view that ignores the environmental consequences of sprawl and the human consequences of foreign objects within the urban anatomy.

Our quality of life is woven together with public and private open space. The combination of shelter and open space is served by its movement and life support systems. Service has had priority over shelter in the name of progress, but increasing awareness will lead us to equalize these priorities as we continue to search for a symbiotic future.

Skyscrapers

A measurement system must be able to accurately measure the entire spectrum of possibilities. This applies to all systems from decibels and voltage to metric commodities. In architecture and city design, the measurement range extends from low density residential subdivisions to high density skyscrapers, but density has been an inaccurate measurement tool producing random leadership results.

To test intensity measurement at the skyscraper end of the spectrum, I modified forecast model CG1L and expanded the design specification template to reflect the unique “sky-plane” responsibilities of this building type. This unique requirement deserves a brief history.

The skyscraper emerged as a capacity multiplier during the troubled times of the tenement. Social reform searched for the soul of free enterprise and substituted regulation. It actually became necessary to specify that light, air and ventilation could not be obstructed by the private construction of tall buildings. Freedom, in this case the freedom to dominate, was an inevitable defense; but the public interest could not be ignored. Increased setbacks were required for increased height to permit light and air to reach the right-of-way. The modern ziggurat, or wedding cake building, emerged in response along the street canyons of mega-cities. The setback regulation was called a “sky-plane”. Building form has become more sophisticated along with regulation, but the policy remains the same. It specifies that the public has a right to light, air and ventilation, but inducement must be offered to augment a right-of-way under pressure from the land use activity spawned at street level.

I have adopted a simple pyramid concept for this example similar to the Transamerica Pyramid in San Francisco and have modified Table 1 to reflect the number of sides and the slope involved. Two rows have been added to the bottom of its design specification template for this purpose. The first asks for the percentage reduction in area per side for each additional floor in height. This is the slope of the pyramid face. The second asks for the number of building faces involved. In this case I have used four sloping sides with a total reduction in floor area of one percent per floor. Calculation is based on the assumption that each slope begins at ground level. Each floor of massing potential intersects the sloping plane and potential area per floor is calculated on this basis.

This is a definition of development capacity expectations, not building form. Remember that massing is an imaginary glass enclosure. Its purpose is to establish massing and context parameters for detailed architectural definition. The forecasts in Table 4 define these parameters.

Figure 3: Transamerica Pyramid

Table 5 summarizes the predictions in Table 4 and illustrates the classic relationship between massing and intensity on one hand and context on the other. A ten story building with a 20% open space allocation declines in context benefit to 13.7% BLA. A 200 story building declines to a 1.4% BLA benefit while massing and intensity steadily increase. It is up to us to determine the course between this modern day Scylla and Charybdis.

Table 5: Massing, Intensity and Context as Multiples of BLA from Table 4

Summary

Table 6 summarizes the massing, intensity and context pressures forecast for each example used in Tables 1-4. They have been produced by values assigned to the design specification topics that pertain to each forecast model mentioned. The alternatives to these predictions are infinite because of the scope of topics, the scope of values that can be assigned to each topic, and the anatomy of the topics involved.

Table 6 indicates that empirical observation can be confirmed with an accurate measurement system. Architects understand that the benefit from a given open space allocation declines as additional building mass increases the pressure, or intensity, imposed. I’ve called the level of benefit “context” and suggested a method of measurement to quantify observation and build knowledge. The goal is to replace subjective terms like “over-development”, “pleasing’, and “pastoral” that cannot lead growing populations toward symbiotic natural relationships.

Table 6: Massing, Intensity and Context Summary for Tables 1 – 4

In architecture, pressure is called “intensity”. Table 6 indicates that pressure can be measured with three readings that I’ve called composition indices. Like blood pressure, these readings indicate the current state of health for a far more complex anatomy, but blood pressure has a frame of reference. Architecture and city design have yet to adapt a method of composition measurement that can place subjective observation into an objective research system.

If you look at any horizontal row in Table 6 you will see that context declines as massing and intensity increase with building height when all other design specifications remain constant. If you look at a column, however, you will see the influence of separate design specification templates. The increase in massing, intensity and context is not a consistent increase from single-family homes to high-rise buildings because these templates contain different topics related to their specific land use family and design premise. In other words, the columns show a trend toward declining context as mass and intensity increase with land use family and design category, but there are too many design specification topics and values in each category to make this more that a trend among categories. In other words, a corporate office in a park could have a better context reading than a single family detached home on a 6,000 square foot lot with 50 feet of frontage because of the different design specification values involved. Building additions would then increase these mass and intensity readings as the context reading for each declines.

In summary, medicine has learned to correlate blood pressure with the health of an anatomy that is a gift. We are now attempting to interpret the health of an environment that is a gift, and we have imposed cities to shelter growing populations on and in this gift. Science would recognize these cities as a parasite facing extinction because there is no “land without end” just as there is no flat earth. The gifts we have been given demand correlation and the next level of awareness will come to grips with the scope of our responsibility. The more common term for correlation is “adaptation”. If a species does not adapt it faces extinction from internal competition and external exposure. It is an inevitable outcome of failure, and we have been given a gift that enables us to adapt with the design decisions required for correlation. Science has named mutual benefit “symbiosis” and it is a worthy goal for our next level of awareness.

I have tried to resist ending with a musical analogy; but the composition indices of massing, intensity, and context are too tempting. If a city is an orchestra, its instruments are forecast models in the DCE collection. Each instrument has three strings; one for each of the three composition indices mentioned. Finger placement on these strings is defined by the values entered in the instrument’s design specification template. Sound is a function of the template, the instrument and the musician. A symphony is a correlation of templates, instruments, and musicians. Acoustics is an environmental response. If you find a composer to be a mystery and his composition a riddle within an acoustic enigma, the challenge to create urban symphonies within symbiotic cities surrounded by environmental judgment should become apparent. Less is known, more is expected and relief by escape from the auditorium is an illusion.

Postscript

Some may have noticed that the Derivation section of this essay explained that:

Mx = GBA / BLA, or

Mx = ( f * BCA) / (CORE + S), and

Ix = Mx / S

The value S in the extended Mx equation helps to express a simple numeric relationship between development capacity GBA and buildable land area BLA. The result Mx expresses capacity as a multiple of the buildable land area but does not explain the declining benefit from a given project open space allocation as building height, mass and capacity increase.

When increasing mass Mx reduces the benefit from a given project open space allocation, the result is an increasing level of intensity Ix. The opposite is also true. Increasing project open space S decreases the intensity from a given building mass Mx. This theorem has been expressed with the equation Ix = Mx / S.

The value S in the Ix equation is a percentage of the BLA that cannot exceed 99.99%. As the percentage increases and Mx remains constant, intensity Ix declines. A value of S = 100% is a park without building mass and the entry should produce an error message. A value of S = 0.0% is a building without project open space, but the value defaults to 0.0001% because zero would produce the lowest rather than the highest intensity reading when no project open space is provided.

Table 1: Massing, Intensity and Context Summary for CG1L Design Premise