6.4.7 RESIDENTIAL DENSITY

   A.   Purpose

      This Section provides uniform methods for determining residential densities on individual sites .

   B.   Applicability

      Residential density for all residential projects is calculated as follows.

      1.   Residential density in residential projects is based on one dwelling unit per minimum size parcel by area, exclusive of any street and drainageway dedications or exclusive use easements. Because the acreage of a parcel used for street and drainageway purposes differs for each development  project , it is difficult to provide a simple calculation that would give an exact density figure.

         The following provide two methods of calculating approximate density for a project . The number of units obtained through these calculations is an estimate and can only be verified by the actual design of the project . Should there be a need to express a density ratio per acre , for comparison purposes only, such ratio will be calculated using the second method assuming 30 percent of the site would be used for streets , drainageways, or other uses whose acreage is not included to calculate allowable density .

         a.   The first method of calculation gives the highest possible density that can be achieved on a parcel . However, to achieve this density , the following two design criteria must be present. (See Figure 6.4.7-A Residential Density , Method 1)

            i.   The property can be developed without additional dedications for streets , drainageways, or exclusive use easements.

            ii.   Each lot is the minimum size permitted by the underlying zone .

            The site area , expressed in square feet, is divided by the minimum lot size permitted by the underlying zone .

            Site Area : 71,400 square feet (sf) or 1.64 acres
            Minimum lot size : 7,000 sf
            Approximate No. of Units   = Site Area ÷ Minimum Lot Size
                        = 71,400 sf ÷ 7,000 sf
                        = 10.2 units
                        = 10 units + .2 remainder
               Approximate Density   = Units ÷ Site Area
                        = 10.2 units ÷ 1.64 acres
                        = 6.22 dwelling units/acres

Figure 6.4.7-A Residential Density , Method 1

         b.   The second method assumes that the project design requires dedication of either streets , drainageways, or exclusive use easements or will have other site conditions that do not allow every square foot of the property to be included in an individual lot . Also, due to varying widths of street and drainageway rights-of-way and lot configurations, it is impossible to project an exact number of units or lots that can be achieved. Since the amount of site area used for streets , drainageways, etc., varies from project to project , it is necessary to approximate the amount of site area by percentage that will be needed for those purposes. It will be assumed, to illustrate the calculations, that 30 percent of the site area will be utilized for such purposes. (See Figure 6.4.7-B Residential Density , Method 2)

            The calculation is the site area , expressed in square feet, minus 30 percent of the site area , divided by the minimum lot size permitted by the underlying zone .

Site Area : 87,120 square feet (sf) or 2 acres
Minimum lot size : 7,000 sf
Site area for streets, etc.: 26,136 sf (approximately 30%)
Approx. No. of Units   = (Site Area - 30% of Site Area ) ÷ Minimum Lot Size
         = (87,120 sf - 26,136 sf) ÷ 7,000 sf
         = 8.71 units
         = 8 units + .71 remainder
Approx. Density   = Units ÷ Site Area
         = 8 units ÷ 2 acres
         = 4 dwelling units/acres

Figure 6.4.7-B Residential Density , Method 2

      2.   Residential density in multifamily projects developed is calculated in the following manner.

         a.   Multiply the area of the site , in acreage, by the density (units per acre ratio) permitted by the underlying zoning.

               Example:
               Units Per Acre Ratio: 15.0
               Project  Site Area : 6 acres
               Calculation:
               Units per acre x site area = no. of units
               15 x 6 = 90 units

         b.   Exception. Any site area  dedicated or sold at nominal cost to the City for public purposes is included as part of the site area for calculation of density , provided:

            i.   The additional density is less than 10 percent of the density permissible for the rest of the site area ;

            ii.   Such dedication was not a condition of approval for applications, such as, but not limited to, rezonings or variance requests;

            iii.   Such dedication does not include right-of-way  dedicated as part of a subdivision  plat ; and

            iv.   A legally binding agreement to dedicate or sell at nominal cost to the City is submitted as part of the application.

      3.   Residential density in Flexible Lot  Development  projects is based on the developable area (as defined in Section 11.4.5 Definitions - D) of the site .

(Ord. 11171, 5/20/2014)