DPWES Letters to Industry


Land Development Services
12055 Government Center Parkway
Fairfax, Virginia 22035
703-324-1720, TTY 711

January 11, 2007
07-02

New Procedure for Reviewing for Shape Factor

On December 4, 2006, the Board of Supervisor’s adopted amendments to the Zoning Ordinance, Subdivision Ordinance and Public Facilities Manual establishing criteria for regulating the shape of new lots in subdivisions proposed for certain residentially zoned districts. These amendments became effective on December 5, 2006.

For the most part, building lots within residential subdivisions are generally found to be conventional or rectangular in shape. However, there have been a growing number of irregularly shaped lots that have exhibited characteristics such as elongated appendages, extreme width to depth ratios and lot lines with sharply acute angles that have proven to be problematic for the home owner. Such irregularly shaped lots have made it very difficult for homeowners to readily ascertain lot line locations, have perpetuated difficulties with yard and septic field maintenance and have resulted in lots that are generally inconsistent with the intent of the Zoning Ordinance.

Providing the development community with a simple straightforward approach to designing lots that were more regular in shape led to the concept of a Shape Factor. A Shape Factor consists of a mathematical measurement of a lot’s compactness and is defined as a non-dimensional ratio between the lot perimeter squared and the lot area. Shape Factor is an easily applied method that can be universally used to categorize the relative shape of a lot in terms of its regularity of form. Shape Factor requirements will apply to all new lots in subdivisions proposed for the R-E, R-1 through R-5 and R-8 districts as well as the single family portions of developments in the PDH, PDC and PRC districts which are not depicted on an approved development plan. These requirements will not apply to existing lots (e.g. lots recorded prior to the effective date of this ordinance), lots depicted on an approved proffered development plan, lots which are subject to an approved Special Exception for cluster development, or lots depicted on a Preliminary Plan which was approved prior to December 5, 2006.

The procedures for evaluating the configuration of a lot and the criteria for implementing these procedures are as follows:

  • Lots that are subject to this amendment shall be required to have a Shape Factor of 35 or less based on the Shape Factor formula of: SF = P2/A where P = the perimeter of the lot and A = the area of the lot.
  • A lot with a Shape Factor greater than 35 but less than 50 may be permitted by the Board of Supervisors through the approval of a Special Exception.
  • Lots within the R-2, R-3, and R-4 Districts which are approved by the Director for cluster development shall exclude the pipestem portion of a pipestem lot from the Shape Factor computation.
  • On subdivision plans where the lot configuration is subject to the Shape Factor limitations, the Shape Factor shall be depicted for each lot within the subdivision.

Procedures

Effective immediately, on all subdivision plans where the lot configuration is subject to the Shape Factor limitations, the Shape Factor for each lot within the proposed subdivision shall be depicted on the Subdivision Plan. Shape Factor values for each lot should be put in tabular form (See example included below) and should be included on that portion of the plan where the overall lot layout of the subdivision is shown. To facilitate the early identification of potentially problematic lots, it is strongly encouraged that the Shape Factor information be included on all Preliminary Subdivision Plans as well.

Lot Number Lot Perimeter Lot Area Lot Shape Factor
1      
2      
3      

Where the Shape Factor of a lot is greater than 35 but less than 50, specific criteria has been set forth within the Zoning Ordinance whereby the Board of Supervisors, through the approval of a Special Exception application, may permit these lots. Information regarding the submission and processing of a Special Exception application can be obtained through the Zoning Evaluation Division of the Department of Planning and Zoning either by contacting them by telephone at 703-324-1290, TTY 711 or via e-mail.

If you have any questions, please contact Environmental and Site Review Division at 703-324-1720, TTY 711.


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