The prevailing setback is the most frequently occurring distance between buildings and the street and interior property boundaries in the development zone of the subject property. Maintaining the prevailing setback protects the historic and visual character of the street. The figures which follow give several examples of prevailing setbacks in the Tucson metropolitan area.
As shown in Figure 6, row houses on this block of El Presidio HPZ are built in the Spanish-Mexican vernacular tradition with no side or front setbacks. Their front elevations (facades) are all located on their front property lines. The effect of this zero lot line could be achieved without actually locating the building on the property line.
In cases where a front building setback is provided, a high wall or fence may be located on the property line to allow the building itself to be set farther back. This design solution would reinforce the continuous and cohesive sense of enclosure along the street while providing for the unique needs of the property owner. Zero lot line design does not eliminate other Code requirements, such as fire walls and on-
drainage.
Figure 7: Comparison of Prevailing Setbacks shows the contrast in front and side setbacks between blocks.
In the area represented in Figure 8, the setbacks from interior property lines do not follow a regular pattern. In this example low density development has been incremental and informal and has resulted in the preservation of valuable native vegetation. In this case, determining the prevailing setbacks entails an evaluation of both the character of
design in the entire development zone and close scrutiny of setbacks of adjacent properties.
Figure 9: Anglo-American
Design illustrates front setbacks and a typical streetscape. A uniform setback from the street reflects
planning practices common in subdivisions built after the arrival of the Southern Pacific Railroad in Tucson. The uniform front setback is a primary factor in giving the street its character. The goal in both new construction and renovation is to maintain the prevailing front yard setbacks.
The effect of disrupting the prevailing front setback is shown in the schematic in Figure 10. In this example, the effect of discontinuity of the streetscape would be the same whether the offending structure is a room addition, a carport, or a screen or security wall built on the front property line. In each of these instances, the prevailing setback would be compromised.
