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)

6.5. PRINCIPAL LAND USE

6.5.1. ONE OR MORE PRINCIPAL USES , SEPARATE PROJECTS

   One or more principal uses conducted as separate projects on a parcel is considered individually in determining the respective Land Use Classes and dimensional standards

6.5.2. TWO OR MORE PRINCIPAL USES , SAME PROJECT

   Two or more principal uses conducted as a single project , which integrates elements of the various uses, such as, but not limited to, vehicular parking, vehicular and pedestrian access, refuse collection, and loading services, as common use among the various uses in the project , shall have dimensional standards applied as follows:

   A.   Two or More Uses, Same Dimensional Standards

   On projects with two or more uses that have the same dimensional standards, the dimensional standard requirements shall be applied on the site as if there were only one use.

   B.   Two or More Uses, Different Dimensional Standards

   Projects without a residential component shall calculate the residential density (RAC), setbacks and the minimum lot size standards separately for the residential use. All other uses shall use the dimensional standards of the principal use having the least restrictive dimensional standards.

6.6. ACCESSORY USES , BUILDINGS , AND STRUCTURES

   Accessory uses and buildings are permitted in all zoning districts . Those land uses and buildings associated with and incidental to a principal building are accessory and subject to the provisions described below.

6.6.1. ACCESSORY USES

   In all zones , an accessory use shall comply with the following:

   A.   The use shall be incidental or secondary to the principal use and is located on the same parcel as the principal use ;

   B.   The use shall be intended for the occupants, residents, customers, employees, lessees, or guests of the principal use ;

   C.   The use shall not substantially alter the exterior appearance or character of the principal use or building to which it is incidental ; and,

   D.   Animals may be kept for personal use in all zones subject to Tucson Code, Chapter 4, and any applicable health regulations.

   E.   Medical Marijuana Designated Caregiver Cultivation Location

      1.   A designated caregiver may cultivate at their residence for a single qualifying patient subject to compliance with A.R.S. § 36-2806.01;

      2.   All conditions and restrictions for medical marijuana dispensary off-site cultivation locations apply except that the designated caregiver cultivation location cultivation area is limited to a total 250 square feet maximum, including any storage areas; and,

      3.   More than one designated caregiver may co-locate cultivation locations as long as the total cultivation area does not exceed 250 square feet maximum, including storage areas.

   F.   Medical Marijuana Qualifying Patient Cultivation Location:

      1.   A qualifying patient may cultivate at their place of residence subject to compliance with A.R.S. § 36-2806.01; and,

      2.   A qualifying patient, cultivating marijuana, shall comply with all lawful, applicable health regulations, including those promulgated by the Arizona Department of Health Services and any other authorized regulatory agency.

(Am. Ord. 11890, 12/7/2021)

6.6.2. ACCESSORY BUILDINGS AND STRUCTURES

   In all zones , the buildings used for accessory uses shall comply with the following:

   A.   The standards of this Section 6.6.2 apply in all zones to buildings used for accessory uses , except as noted in the following:

      1.   A structure if five feet or less in height and ten square feet or less in area, such as a doghouse, a refuse container enclosure, or play equipment.

      2.    A shelter for food producing animals if six feet or less in height and 16 square feet or less in area.

   B.   An accessory building shall be built only on a lot occupied by a principal building or use;

   C.   An accessory building shall be developed in accordance with the dimensional standards of the principal land use , except as provided by this section and, when applicable, Sections 6.6.3, Residential Uses, and 6.6.5, Urban Agriculture Uses and Activities;

   D.   An accessory structure , except for an accessory dwelling unit , that exceeds the allowable height of a wall within a perimeter yard and is detached from a principal structure shall comply with the perimeter yard width standards of the principal structure , except that the accessory structure may be built to a parcel line with the consent of the adjoining or, when separated by an alley, adjacent property owner(s) or as permitted by Section 6.6.5, Urban Agriculture Uses and Activities;

   E.   Accessory structures , such as light poles, flagpoles, and other tall and narrow structures that are similar, shall be exempt from the setback requirement. Amateur radio towers are exempt from the setback requirement and are allowed to a maximum height of 100 feet;

   F.   An accessory building , except for a stable or enclosure for animals , may be attached to a principal building , provided that its construction complies with the development requirements of the principal building ;

   G.   The use of solar energy collectors for the purpose of providing energy for heating or cooling shall be permitted in all zones , whether as part of a principal building or as an accessory building . Such solar collection devices shall not be included in computing lot coverage ;

   H.   All structures for livestock and other large farm animals such as ratites, as defined in the Tucson Code Chapter 4, Animals and Fowl, shall be set back at least 50 feet from all property lines , except corrals that shall be set back ten feet from all property lines . In addition, the proximity of corrals and barns or other structures for large farm animals from a dwelling unit on adjacent property shall be in accordance with Tucson Code Chapter 4, Section 4-27;

   I.   The maximum height of a wall or fence within a perimeter yard shall be six feet; however, the wall or fence may be higher than six feet, but no higher than ten feet, if: (See Figure 6.6.1-A, Height of Wall or Fence within a Side or Rear Perimeter Yard .)

      1.   At least 75% of the area above six feet in height is left unobstructed and open through the use of architectural elements, such as arches, columns, or wrought iron;

      2.   Part of, or located on top of, a retaining wall no higher than ten feet measured from design grade and no higher than six feet measured from the top of the retaining portion of the wall;

      3.   A greater height is required through the rezoning process or the special exception land use process; or,

      4.   A greater height is required by a specific UDC standard.

   J.   In nonresidential zones , walls or fences, as permitted in Section 6.6.2.I above, may exceed the height standards, provided the wall or fence complies with the perimeter yard standards applicable to buildings on the site ;

   K.   Accessory uses , buildings , and structures are not required to provide additional parking, landscaping and screening, or loading spaces beyond what is required of the principal use .

Figure 6.6.1-A: Height of Wall or Fence Within a Side or Rear Perimeter Yard

(Am. Ord. 11171, 5/20/2014; Am. Ord. 11328, 12/8/2015; Am. Ord. 11890, 12/7/2021)