How Zoning Works: Allowable Bulk Plane

The bulk plane is really a series of planes which limit the allowable volume of space the building can occupy. As with the height limitations, the bulk plane requirements are separated into limits for the front 65% of the lot and the rear 35%. The purpose of the bulk plane is to allow adjacent neighbors access to sunlight and to maintain privacy. Because of the sunlight requirement, the planes follow the length of the property and slope inward at a 45 degree angle. Typically the vertical leg is 17′ in front and 10′ in the rear and is horizontally located above the property line. The top plane is determined by the building height limitation. To learn more, see the bulk plane drawings in this section, page 13.1-16, and figure 13.1-21.

Because the bulk plane can cause acrimony between neighbors, especially in cases like ours with city infill projects, the measurement requirements are very detailed. The information below is spread over several chapter 13 pages.

  1. Base plane .. The base plane is an imaginary horizontal bottom plane from which the vertical legs of the bulk planes are measured.
    1. The vertical position of the front base plane is determined by an average of the vertical spot elevations, shown on the survey, at the face of the house (not the porch) plane which intersects the property line.
    2. As an example, if the west spot elevation is 94.00 and the east spot elevation is 96.00, the front and back edges of the base plane are at elevation 95.00. The rear base plane is the same except that the vertical spot elevations are taken at the rear property corners. To learn more, see page 13.1-2.
  2. Side wall height .. Depending on the chart shown on page 5.3-5, the side wall is typically 17′ in the front and 10′ in the rear. Page 13.1-16 shows some very specific rules of measurement, but 17′-10′ is ok for our purposes.
  3. 3. Height .. The height of the bulk plane is shown on page 5.3-5 but for our purposes is typically 30′ in front and 17′ in the rear. See page 13.1-12 to learn more.

Please let me know if you have any questions regarding the above.

Steve Culbertson