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Wednesday, November 10, 2010


            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

The following articles can be read on my blog, Cities and Design, at

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.

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