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A build-out analysis projects the amount and location of development that may ultimately occur in a specified area as permitted by current land development ordinances. It enables a community to test the reality of its development regulations against its vision for its future.
People often assume that their community's zoning regulations will protect them from inappropriate development, but conventional zoning and subdivision regulations typically allow development on all buildable land. A build-out analysis allows a community to see, under its existing regulations, what their community will look like when all land is developed to the extent allowed under current law. The analysis can also include the impacts from permissible development on the tax base, traffic, school enrollment, park needs, sewage and water facilities, natural and historic resources, farmland and rural landscapes, and overall quality of life. The results of the analysis typically are conveyed through maps and charts. The analysis enables officials to make more informed decisions in their development regulations and planning for the future.
There are typically two phases in conducting a build-out analysis: Phase I visually depicts changes on a map, and measures additional housing units and non-residential square footage that could be built under existing zoning regulations. Phase II quantifies the impact of the additional development. A summary brings together the critical information and conclusions in an easy-to-understand way.
A computerized geographic information system (GIS) is helpful. GIS allows data to be combined, managed, manipulated and analyzed. A GIS can be used to determine the number of additional dwelling units and non-residential square feet that could be built on developable land in the study area under the existing zoning regulations. A GIS can provide a user-friendly model for electronically layering maps to allow users to easily visualize where development in a community might occur. Depending on the software, this information can then be shared via the internet without the requirement that end-users purchase GIS software.
If a community wants to take the analysis one step further, a graphic artist could use the Phase I results to prepare sketches of possible future street scenes. (The computer software Community Viz could be applied to this purpose.)
Before starting, you will need to determine the scale at which you will conduct the analysis. Although the more detailed the analysis, the greater level of accuracy and information you will have, increasing detail will also increase the amount of resources you will need to invest in creating the analysis.
At the micro-scale, each parcel is analyzed to account for zoning requirements and physical constraints.
At an intermediate scale, parcels are analyzed using the same constraint parameters across the study area. For example, all parcels within the study area could be grouped and evaluated as a whole by zoning districts. Although this approach is useful if time and data availability do not allow for a more detailed analysis, whether or not this scale will give sufficient accuracy will depend on the intended use. This level of analysis will not allow a locality to know where exactly development can occur.
More detailed information about scale can be found in the paper “Build-Out Analysis in GIS as a Planning Tool With a Demonstration for Roanoke County, Virginia” by Mary A. Zirkle.
First, construct a base map of your community. The base map should show the basics, such as:
The base map should:
After the base map is created, the next step is creating overlay maps that show land that may be developed further. Then calculate what development may occur by applying the zoning regulations to the total acres developable. This will yield total buildable dwelling units and/or total buildable non-residential square feet by zoning district.
Communities that have a high percentage of undeveloped or underdeveloped land may want to do staggered overlays showing the possible progression of growth. For instance, the first might show growth along major roads and on large parcels. The next overlay might show growth on the next most desirable parcels. The last could show growth on the least desirable parcels.
Phase II is a quantitative analysis of the impact of the changes detailed in Phase I. Numbers to calculate might include changes in:
Additional analysis should be based on the priorities and capacity of the municipality and is not a requirement of a build-out analysis. In the impact analysis, a community determines what is important to them. Additional factors that might be considered are:
The following is a detailed discussion of how a build-out analysis is typically constructed. Note that most build-out analyses use Geographic Information Systems (GIS). GIS is used to determine the number of additional dwelling units and non-residential square feet that could be built on developable land in the study area under the existing zoning regulations. The number of additional dwelling units can be converted to population, based on current or projected household sizes per municipality, and the number of additional non-residential square feet can be converted to employees, based on employment generation standards from The Fiscal Impact Handbook by Robert W. Burchell and David Listokin.
First, Geographic Information System (GIS) data sets are gathered which include parcel data, land use, environmental constraints such as floodplains and wetlands, and zoning districts. The total acreage of developable land is calculated by zoning district. Undeveloped land (vacant, wooded, and agricultural) and land deemed appropriate for redevelopment are considered “developable”. Environmentally constrained lands (floodplain, wetlands, steep slopes, and any other areas where development is regulated) are then subtracted from the total developable acres. An additional 10% is subtracted from the resulting amount in residential zoning districts to account for streets and infrastructure, with the remainder equaling the net total acres developable by zoning district.
The particular zoning regulations per district are applied to the net total acres developable to yield total buildable dwelling units and total buildable non-residential square feet. Many assumptions in interpreting the zoning regulations will need to be made. For example, in a mixed use district, it is advised to assume the greatest percentage of non-residential uses and of higher density residential uses permitted per development.
To calculate the achievable Floor Area Ratio (FAR), which is often different than the permitted FAR, use the formula:
FAR = Impervious Coverage Ratio
1 + 400SF (square feet)
# of Stories Parking ratio
Impervious Coverage Ratio: The maximum percentage of the site that may be covered by impervious surfaces (buildings, parking lots, driveways, etc) stated in the zoning ordinance.
Number of Stories: Manufacturing and warehousing type uses are always assumed to be built as one story. Likewise, retail is assumed to consume one floor only. Generally, only offices are deemed likely to be built on more than one story, for which the maximum number of stories permitted, stated in the ordinance, should be used.
400 SF: A standard amount of impervious coverage per parking space, aisle, and associated driveway space.
Parking ratio: The ratio stated in the zoning ordinance per gross square feet of building space. For example, a common parking ratio requirement for office use is 1 space per 200 SF of building space. The parking ratio in this case would be 200, meaning 200 SF per 1 parking space.
Developable land that will be developed in the near future (indicated by building proposals that were expected to be approved shortly, approved building proposals, and land under construction) should be subtracted from the net total acres developable prior to the application of the zoning regulations. Data on dwelling units and non-residential square feet for these areas can then be added to the buildable dwelling units and buildable square feet found after the zoning regulations are applied.
Employment generation can be based on standards from The Fiscal Impact Handbook by Robert W. Burchell and David Listokin. The following standards can be applied to the district’s most prominent uses:
Shopping Centers: 1 employee per 500 SF GLA (gross leasable area)
Offices: 1 employee per 250 SG NLA (net leasable area)
Industrial Plants: 1 employee per 300 SF NLA
Warehouses: 1 employee per 750 SF GLA
Build-out analysis is not just for communities with vacant land. Any community with property that has not yet been developed to the full extent allowable under law might benefit from a build-out analysis.
Patty Elkis, PP, AICP, Associate Director, Planning Division, Delaware Valley Regional Planning Commission prepared the first draft of this document; Peter Claggett of the Chesapeake Bay Program and USGS reviewed it. A substantial portion of the original text of the main description was quoted directly or adapted from the U.S. Environmental Protection Agency website (http://www.epa.gov/greenkit/build_out.htm).
Copyright © is held by the Pennsylvania Land Trust Association
Text may be excerpted and reproduced with acknowledgement of ConservationTools.org and the Pennsylvania Land Trust Association.