In real estate and land use planning, a zero lot line refers to the construction of a building directly on one or more of the property’s boundary lines. This design eliminates the typical setback requirement on that side of the lot.

Zero lot line construction is commonly used in commercial developments, such as stores built up to the sidewalk, and in certain residential projects to maximize usable space. The arrangement is subject to zoning regulations and building codes that govern setbacks and fire safety.