Cities and Design: November 2010

Monday, November 29, 2010

CITY DESIGN WITH SPACE

Design with space depends on the concept of core area development capacity and its relationship to the off-setting project open space provided. (Core area is the land remaining for building mass and parking after all other demands are subtracted from a gross land area of any size. If parking is not required, or placed underground, the entire core area is available for building mass that is often referred to as building height and area.)

Table 1 explains the distillation of core area. Public rights-of-way and improved or paved easements, if present, are first subtracted from a gross land area. (If this is a forecast the area subtracted would be an estimated percentage of the gross land area.) The net land area remaining is further reduced to buildable land area by subtracting all unbuildable areas such as, but not limited to, ravines, marshes, ponds, and unstable soil, if present. Buildable area is reduced to core area by subtracting the open space present or planned in addition to miscellaneous pavement, driveways and loading areas. (If this is a forecast, the areas subtracted would be estimated percentages of the buildable land defined.) The core area that remains is available for building mass; and parking, if required. (Parking is only open space in the minds of those who wish to increase intensity.) When reviewing Table 1, keep in mind that the areas mentioned can represent those of one project, or the sum of many areas within a larger plan.

After core area is identified, it becomes possible to forecast gross building area potential based on the forecast model chosen and the design specification values entered. This potential has been called development capacity, and the square feet of gross building area present or predicted per buildable acre has been called intensity. Intensity can be calculated per gross or net acre; but when large unbuildable areas are involved, these statistics distort the intensity that people experience within the buildable area.

The choice of a development capacity forecast model is influenced by the land use category involved, but this is a simple choice among residential, non-residential or mixed-use alternatives. A non-residential choice would lead to Table 2. A series of decisions in Table 2 leads to a forecast model. The first decision involves the parking system contemplated. This leads to a choice among the parking design options available within the system chosen. From this point, the path leads to one of two forecast models. The choice depends on the information given. Gross building area predictions are based on a given gross land area. Gross land area predictions are based on a given gross building area objective. The given areas can be of any size and do not need to be restricted to one project.

For instance, if the CG1L forecast model is chosen in Table 2, Table 3 illustrates values that can be entered in its design specification template to forecast the core area of a given gross land area. Additional values are entered to calculate the development capacity of this core area in the GBA column and the intensity of this capacity in the SFAC column. Any change in the values entered alters the forecast. If the open space percentage is increased from 30% for instance, core area shrinks along with gross building area capacity, or design specification values must be adjusted to maintain the same capacity. If open space is decreased, the core area increases along with its gross building area potential unless other specification values are also modified.

It should be apparent that open space is a major design specification value that affects the amount of core land area available within our built environment. When combined with other design specification values, it determines the scope of activity and population that can be sheltered within any specified area. Context refinement adds form, function and appearance to intensity decisions that lead to the places we create.

Building height can be increased within a core area, parking requirements can be eliminated and open space can be reduced in the buildable area to increase core area intensity, but these options can be used to extremes that prompted original efforts to protect the public health, safety and welfare. When these options are exhausted, the only way to increase core area development capacity is to buy more land. This is the dilemma we face on a planet of limited resources and expanding population. Open space must be protected beyond the artificial environment we build to ensure the survival of life on the planet, but it must be protected within the places we build to relieve intensity. The specifications required remain to be determined, but common sense should tell us that open space is essential to our quality of life and agricultural capacity, while also part of an ecology of survival we threaten with unlimited consumption.

Footpaths document our first explorations of space, but the land discovered is simply an island in a sea protected by a thin film of atmosphere at risk. Improved movement systems expanded our control. Shelter was built and life support systems were extended. As a result, land was converted from its natural function to an artificial domain we call the built environment. In my lifetime this domain has expanded to serve growing populations while inner cities have been abandoned to escape intensity. This has produced sprawl without economic stability that continues to threaten its source of survival.

Sprawl tells me that we have not learned to design with space as we construct the four divisions of our built environment. We use too much or too little and mistakes are reflected in blight, social alienation, economic instability and psychological distress. We have all seen horrendous relationships among shelter, movement, open space and life support structures within cities. We consider open space a void to be “improved” and resistance is considered “taking”. Sprawl continues as we struggle to recognize natural realities that face our abstract world with a power we cannot dominate without consequences.

It is becoming apparent that we must adapt to life within limits since the space beyond cannot be consumed indefinitely. It also means that we must adapt our concept of agriculture to resist urban sprawl; to adapt open space requirements within cities to offset excessive intensity; and to recognize that life within limits will require the redevelopment of blight rather than the abandonment of central cities. This does not mean that economic penalties can be imposed on those saddled with the mistakes of our past, but that our abstract financial concepts must adapt to recognize the goal, which is design with space that protects the survival, patterns and dignity of all life on the planet.

We have much to learn about the space that must be protected beyond our cities and the space we must preserve within, since shelter and movement options can respond to population growth with overwhelming intensity. We are now coming to realize, however, that low intensity cannot serve population growth without threatening the health, safety and welfare of the planet.

Learning to shelter the activities of expanding populations within geographical limits will require a thorough understanding of intensity and context design. Anything less will continue our consumption of a planet that cannot speak, but who reacts without compromise. It is we who must learn its language, since it has no need to explain that we are not a gift. It is the gift and we are expected to take responsibility. Forecasting our development capacity options within sustainable limits is a step in this direction.

Author Note: Land Development Calculations has been written to assist many professions who wish to build the knowledge required to design with space. It forecasts development capacity in relation to the land consumed. This unlocks the ability to forecast anything that is a function of the gross building area predicted such as, but not limited to, construction budget, population capacity, traffic generation, return on investment and yield per acre (for comparison to a city’s average annual operating expense per acre).

The following articles can be read on my blog, Cities and Design, at http://wmhosack.blogspot.com/:

1) "Replacing Density" discusses its leadership weakness and intensity alternative,

2) "The Limits of Shelter Capacity" provides expanded detail regarding intensity,

3) “The City is a Farm” discusses the relationship of intensity to economic development,

4) "The Disorganized Zoning Ordinance" outlines the legislative confusion that impedes leadership progress,

5) “Examining Architecture” takes a closer look at a piece of the city design puzzle,

6) “The Variance Trap” illustrates development regulation weakness with a residential forecast model from the Development Capacity Evaluation (DCE) software collection,

7) “City Design with Space” discusses the overlooked role of project open space with a non-residential forecast model from the DCE collection,

8) “The Core of Our Built Environment” identifies the nucleus of development capacity

9) “Ponzi Schemes and Land Use Plans” offers an alternative to annexation and sprawl.

10) “Where Does Sustainability Begin?” discusses the importance of land in a competition between our natural and built environments.

11) “Economic Development Is Missing a Strategy” discusses the intelligence and strategic planning required to identify economic development objectives on the road to a sustainable future.

These articles have been deleted from my blog but are available upon request:

1) “The Concept of City Design” includes an overview and suggested research agenda,

2) “Politics and Planning” is an argument in support of the effort, and

3) “Context Measurement” outlines a suggested research yardstick.

Wednesday, November 10, 2010

THE VARIANCE TRAP

A zoning variance is intended to mitigate the hardship of general regulations applied to a unique circumstance, but often represents a lack of confidence in the regulation itself. In many cases there is good reason, because specific requirements are often uncoordinated attempts to achieve poorly defined goals. The following is a brief sketch of the confusion that surrounds our attempts to reach goals with density, parking and building height regulations.

I began my career listening to discussions of permitted residential densities, heights, and required parking. I started wondering if anyone understood the combined impact of these requirements, especially when additional regulations, such as landscape requirements within a parking lot, were being considered. I quickly realized that no one could accurately forecast implications, and all of us relied on intuition and claims of experience.

As an example, a density of 80 dwelling units per acre was permitted along with a building height of 15 stories and a parking requirement of 1.5 spaces per dwelling unit. When a developer attempted to design within these parameters using a grade parking lot, he couldn't come close to 80 dwelling units per acre. This encouraged him to pave every potential square foot in an attempt to reach his authorized density, and this began my search for a way to define realistic expectations based upon a thorough understanding of design fundamentals.

Table 1 explains the point using a forecast model from the Development Capacity Evaluation software collection. This model is designed to address residential, grade parking lot design solutions with the parking lot around, but not under, the building. It has two primary panels entitled, “Design Specification” and “Planning Forecast”. A land area of 5 acres is given and Arrow 1 points to the permitted density. Arrow 8 points to the number of dwelling units implied by this density. Arrow 3 points to the parking requirement and Arrow 2 points to the land area estimate per parking space. (The area shown implies that very little internal parking lot landscape is planned.) Arrow 4 indicates that 80% of the gross building area will remain for habitable space. (This means that 20% of the gross building area is estimated for wall thickness, circulation, mechanical areas, etc.) Arrow 5 points to the average dwelling unit area planned based on the dwelling unit mix specified. (This is a critical forecasting value that is rarely considered.) Arrow 6 points to a minimal open space provision of 10% and Arrow 7 points to a more desirable value of 40%. However, column FLR in the Planning Forecast Panel is zero throughout, indicating that the density and design specification is not feasible, nor is the dwelling unit target of 400.

Table 2 forecasts development implications for a density of 50 when all other specification values remain constant. Arrow 8 points to a reduced target of 250 dwelling units. A 10.2 story building is required and only 10% open space can be provided since 15% requires a 16.4 story building and only 15 floors are permitted. This design specification can easily produce a profitable building in an undesirable context when design with space is dominated by the demand for building capacity.

Table 3 forecasts the development implications of the density 33.43 when all other specification values remain constant. Arrow 8 points to a reduced target of 167 dwelling units that could be constructed on 15 floors with 40% open space, but why build 15 floors when you can create the same number of dwelling units on 2.5 floors with 10% open space and less expense? (You could also build 250 dwelling units with 10.2 floors (round to 10 or 11) and 10% open space as noted in Table 2.) The answer depends on the intensity and context desired within an urban design district of a city design plan.

Note in Table 3 that the parking lot area PLA is constant because the density objective of 33.43 does not change, but that the open space S increases from 0.5 to 2.0 acres as building height FLR increases from 2.5 to 15 floors and building footprint BCA decreases. Changing any value entered in the design specification panel of Table 3 would produce a new forecast for evaluation. This should indicate the spectrum of intensity options available to any project, not to mention the increase in options that occurs when a forecast model representing another design category is selected for comparison.

Unfortunately, a developer who expects a 400 dwelling unit return from a land purchase may first attempt to modify his design specification values when only reaching 167, or 42% of his goal. He may then seek variances to the values required when he still can’t reach the level of expectation encouraged by the density regulation involved, and appointed regulators with diverse backgrounds may feel relief is warranted because of the disparity. This is not in anyone’s interest when the places created and the land consumed occurs by chance mistaken for leadership.

If 40% open space was part of a pedestrian circulation plan however, the 10% option in Table 3 would not meet the urban design criteria established and a variance would clearly contradict the goal.

The development capacity of land is a function of the zoning regulations adopted. Setbacks, densities, building height and parking requirements represent our first attempts to combat fire hazard with building codes and separation; physical and mental health hazard with density regulation and building height limits; and traffic hazard with parking requirements. Open space has been a left-over often reduced with variance approvals and rarely addressed as a specific requirement in zoning ordinances. Its existence by chance is threatened by variance, but its reduction is a hazard that increases intensity and alters context. Specific requirements will raise the issue of “taking”, but space is a design fundamental and an essential ingredient that defines intensity by off-setting building mass and pavement. The lack of space is no less a hazard than the lack of light, air and ventilation since physical and psychological health issues are interrelated. City design with space and intensity can clearly define the goals required, and development capacity evaluation can expose the implications of varying from the plan.

Author Note: Portions of this article were excerpted and edited from the second edition of my book, Land Development Calculations, and its attached forecasting software, Development Capacity Evaluation, v2.0 published by The McGraw-Hill Companies, 2010. The book can be found on Amazon.com.