A setback is a zoning requirement specifying the minimum distance from a property line within which buildings (and sometimes other improvements like decks, garages, or pools) may not be constructed. Setbacks are typically defined per side: front setback, side setbacks, and rear setback. Specific values come from the local zoning code and vary by zoning district (residential, commercial, industrial, mixed-use).
For contractors, setbacks affect site planning and building design. Encroaching into a setback typically requires a variance (a formal request to the zoning board for an exception). Variances can take 2 to 6 months to obtain. Setbacks are enforced through zoning permits issued before building permits; building permits are typically not issued until zoning compliance (including setback compliance) is verified.