Setbacks Define the Boundaries Within Which a Building Can Be Located
Building setbacks are minimum required distances between a structure and a property line (or other reference, such as a street centerline, easement, or waterway). Setbacks are established by the zoning code and serve several purposes: maintaining neighborhood character and preventing buildings from encroaching on adjacent properties; providing fire separation between buildings; ensuring adequate light and air between structures; and preserving visual corridors and street edge conditions. On any site, the setbacks from all four property lines define a reduced buildable area within the site - the "building envelope" - within which all structure must be located. The ARE PA exam tests setback analysis as a fundamental site planning skill that must be completed before any design work begins.
Types of Setbacks
- Front setback (front yard): Minimum distance from the front property line (typically facing the primary street) to the building. Front setbacks are typically the most regulated dimension and often define the neighborhood's street edge character.
- Rear setback (rear yard): Minimum distance from the rear property line to the building. May be smaller or larger than the front setback depending on the district.
- Side setbacks (side yards): Minimum distance from each side property line to the building. Side setbacks are typically smaller than front and rear setbacks for urban and suburban sites, but may be zero in downtown commercial districts that allow buildings at the property line.
- Street-facing side setback: Corner lots have two street-facing frontages; the secondary frontage may have a different (often smaller) setback than the primary front setback.
How Setbacks Are Measured
Setbacks are typically measured as the horizontal distance from the property line to the nearest point of the building (or to the nearest point of the building foundation, in some codes). Overhangs, canopies, decks, and similar projections are sometimes exempted from setback requirements (allowed to extend into the setback zone) up to defined dimensions - for example, a building cornice may be allowed to project 24 inches into the setback. Zoning codes define exactly what elements must maintain the setback and what elements are permitted exceptions.
Setbacks vs. Easements
Easements are distinct from setbacks but have similar effects on buildable area. An easement is a right granted to a party (utility company, adjacent landowner, public entity) to use a portion of the property for a defined purpose. Utility easements prohibit building construction within the easement area. Access easements allow vehicles or pedestrians to cross the property. Conservation easements restrict development within sensitive environmental areas. Unlike setbacks (which are zoning requirements that can be variated), easements are property rights recorded on the deed that cannot be unilaterally removed by the property owner.
Calculating the Buildable Envelope
After identifying all applicable setbacks and easements, the architect calculates the buildable area by subtracting the setback and easement areas from the total parcel area. If the site is 120 feet wide and has 15-foot side setbacks on each side, the maximum building width is 90 feet. Combined with height limits, FAR limits, and lot coverage limits, the result is a precise three-dimensional buildable envelope that constrains all design options.
Key Exam Points
- Setbacks: minimum distances from property lines to building; establishes buildable area within the site.
- Front, rear, and side setbacks may differ; corner lot secondary frontage has its own setback.
- Measured from property line to nearest building point; defined projections may be exempted.
- Easements further reduce buildable area; cannot be removed unilaterally (unlike setback variances).
- Buildable envelope = parcel area minus all setback and easement restrictions.
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