GLOSSARY

Open Parking Garage (Open-Air Facility)

An open parking garage, sometimes called an open-air parking facility, is a parking structure with enough uniformly distributed openings in its exterior walls on two or more sides to be ventilated naturally, as defined in the International Building Code (IBC).

ELEVATION OF ONE TIER: WHAT MAKES A GARAGE OPENOPENINGS ON EACH SIDE ADD UPROOF OR UPPER DECK ALLOWED: OPENNESS IS ABOUT THE WALLSTEST 1: open area at least 20% of the tier’s total perimeter wall areaTEST 2: openings run at least 40% of the tier’s perimeter lengthOpenings uniformly distributed on two or more sides (IBC 406.5.2)
An open parking garage is defined by its wall openings, not by the absence of a roof. Meet the openness tests on each tier and natural airflow replaces mechanical ventilation. Check the code edition adopted locally. Illustrative.

Being open is about the walls, not the roof. An open garage can have a roofed top level, or sit under other occupancies, and still qualify. Under IBC Section 406.5.2, the openings on each tier must total at least 20 percent of the tier’s total perimeter wall area, and their aggregate length must be at least 40 percent of the tier’s perimeter. Interior walls and column lines must also be substantially open. See openness calculation.

Why the classification matters

  • Ventilation. An open garage relies on natural airflow and needs no mechanical exhaust system. A garage that fails the tests is an enclosed parking garage and must be mechanically ventilated under the mechanical code.
  • Size limits. The IBC allows open garages greater height and area than enclosed garages of the same construction type, which is why most freestanding parking structures are designed to be open.
  • Fire protection. Sprinkler requirements for open garages have been changing as editions of the IBC respond to larger vehicles and EV fires. Check the edition the local jurisdiction has adopted.
  • Occupancy. Open garages for private vehicles are Group S-2. See Group S-2.

What can break it

  • Solid facade panels, louvers or screens that block more of the openings than the calculation allows.
  • Below-grade levels, which usually cannot meet the tests and are treated as enclosed.
  • Adjacent buildings or walls too close to the openings to let air move freely.

The Parkonomics view

The open-garage line is one of the most valuable a designer draws. Staying on the open side avoids mechanical ventilation for the life of the building and buys height and area. Treat the openness calculation as a design constraint from the first facade sketch, not a check at permit time, because the screen that makes a garage beautiful is often the one that makes it enclosed.

Related terms: Openness Calculation, Enclosed Parking Garage, Natural Ventilation, Mechanical Ventilation System, Group S-2 Parking Garage, Architectural Mesh

Further reading: The Evolution of U.S. Parking Structures in 2026