Columns, Curbs, and Encroachments: Where the Structure Meets the Layout

The layout is drawn on a clean plan, and then the building intrudes on it: columns land in the parking field, light poles claim stall corners, curbs and wheel stops appear where policy or drainage put them. Each intrusion is small; their accumulation is where good geometry quietly dies. This module carries the rules that keep the intrusions priced and bounded, and the safety case for the intrusions that should not exist at all.

The encroachment budget. Columns in structures extend past the bumper wall into the module; light poles in lots shorten stalls. The rules that keep this survivable: an encroachment should not reduce the module by more than 2 feet, and encroachments should touch no more than 30 percent of the stalls; and where intrusions exceed that 30 percent, the interlock reduction from the previous module must not be taken on top of them, because stacking the discounts produces a module that works only in the drawing.

The column-adjacency rule, and the fallacy it corrects. Short-span practice sometimes lets a column encroach on stall width under the theory that the stall is adequate as long as the door clears the column when it swings. The theory mistakes what the clearance is for. With design vehicles parked on both sides, the clear space for turning into a typical stall is the stall width plus at least 20 inches borrowed from the neighbors' gaps; a wall or column beside the stall confiscates that borrowed space on one side. The correction: widen any stall adjacent to a wall, column, or other obstruction by at least 10 inches, restoring the turning comfort of a mid-bay stall. Skip the widening and the market applies its own correction, worse: drivers park off-center away from the obstruction, crowding the next stall, which crowds the next, and the whole row's effective widths shrink to pay for the one stall the drawing shorted.

Long-span is the encroachment cure. The reason the long-span-versus-short-span decision belongs in the structural module but echoes here: clear-spanning the module removes columns from between parked cars entirely. Long-span buys easy entry without the fender-bender stigma, recovers the floor area columns consume, and, most valuably, preserves the freedom to restripe the entire field as vehicle sizes change across the structure's decades. Short-span columns (typically 18 to 27 feet apart across the stalls, inset about 15 feet from the stall face) cost efficiency, maneuverability, door clearance, and interlock; their legitimate use cases are narrow footprints that need the smaller structural module, and facilities (bus garages among them) where pull-forward exiting is a safety requirement.

Curbs and wheel stops: the case against. Inside the parking field, curbs and precast wheel stops are trip hazards first and vehicle controls second, and the injury data makes the priority vivid: in a single recent year, falls killed over 42,000 people in the US, more than motor vehicles killed (40,698), and past age 65 falls pull decisively ahead, which matters most in exactly the medical facilities whose patrons are oldest. So: no curbs between modules on flat decks, where patrons crossing between bays will find them with their feet; curbs only where local code requires them or drainage genuinely needs them; wheel stops discouraged outright as trip hazards and debris collectors. Where angle parking forces wheel stops anyway, place them in a straight line rather than perpendicular to each stall, because the perpendicular arrangement puts the neighboring stop exactly where the exiting driver steps down, and vans make it worse by seating the driver unusually far forward.