Development capacity of land - Density vs. Intensity

[M II A II R II K]

Replacing Density


September 30, 2010

By Walter M. Hosack

Read More: http://wmhosack.blogspot.com/2010/09...g-density.html

The development capacity of land is equal to the gross building area that can be constructed per acre available. Gross building area however, is simply a volume that provides shelter on the floors involved. The amount provided per acre, in addition to the supporting pavement introduced, is referred to as “intensity” when compared to the project open space that remains. At one end of the spectrum is a small building on thousands of acres. At the other is a high-rise on one acre. In both cases, the square feet of shelter and pavement constructed per acre of land involved is a measure of the physical intensity introduced.

- When gross building area is planned or converted for a specific activity, such as a hospital, the physical level of intensity is also affected by the social activity planned. The combination is referred to as “land use”, and its condition is affected by its economic stability and social acceptance.

- The movement and life support divisions of our built environment open up land for development, but intensity begins with the square feet of building area and pavement provided per acre of land consumed -- in relation to the project open space that remains. This determines the population that can be served, the scope of activity that can be conducted, the economic contribution that can be expected, and the quality of life encouraged.

- Density is a concept in the world of land use planning that is a statistic of performance, but an inadequate leadership metric. There are just too many loose ends that encourage random results because it does not anticipate the design categories, specification variables and mathematical relationships involved. Random intensity is one of these random results. It cannot be controlled by a simple density statistic because it is a function of the relationship between building mass, development cover and project open space on a given land area. Density can report results, but it cannot lead performance because it omits the pressure points of design.

- Physical intensity has three components: building mass, development cover, and project open space. Development cover is a generic name for pavement of various types, such as parking lots and plazas. Project open space excludes unbuildable areas such as ravines and is the amount of unpaved space within the buildable area of any property.

- Building mass is gross building area that is a function of the building height and floor plan involved. The floor plan area can be included with development cover to express the amount of impervious cover present, but this two-dimensional statistic defines balance. It does not define the intensity created by the relationship of three-dimensional form and pavement to open space. This relationship can be defined with equations that relate to design categories and operate with values assigned to their design specification variables.

I = intensity expressed in terms of gross building area sq ft per acre
GBA = gross building area in sq ft
AC = gross land area, GLA: or net land area, NLA; or buildable land area BLA; or core land area CORE in acres

I = GBA / AC




s = a value representing the average gross parking lot area, including landscaped islands, divided by the number of parking spaces provided (different values represent different parking lot designs)
a = the maximum building area permitted per parking space provided






Figure 1 confirms the intuition of many designers and converts this intuition to knowledge that is a function of the CG1L forecast model. The context implications of design specifications, including open space requirements, and the intensity options produced remain to be explored; but there is another point to be made. Figure 1 demonstrates that planning and design issues can be expressed in mathematical terms.