ASCE 7-22 Chapters 26-30 - Wind Loads for Components and Cladding: The Engineering Basis for Garage Door Pressure Ratings

Every garage door pressure rating in pounds per square foot (psf) traces back to a calculation method defined in ASCE 7-22. Chapters 26 through 30 contain the components and cladding (C&C) wind load procedures. These chapters are the engineering authority behind every door specification that includes a design pressure.

What this standard says

ASCE 7-22, published by the American Society of Civil Engineers, is the design standard referenced by both the IBC and IRC for wind load determination. Chapters 26 through 30 address wind loads on buildings.

ASCE 7-22 Chapter 26 describes the design inputs:

"Identifying 3-second gust speeds at specific reference heights ... applying velocity pressure exposure coefficients to adjust for actual site conditions ... using importance factors (Iw values: 0.87, 1.00, 1.15) based on Risk Category."

Chapter 26 establishes the foundational inputs: the design wind speed from the ASCE 7-22 wind speed maps (Figures 26.5-1A through 26.5-1C), the exposure category (B for suburban, C for open terrain, D for coastal), and the building's risk category. The wind speed maps provide ultimate design wind speed (Vult) for four risk categories. Denver sits in the 115 mph Vult zone for Risk Category II buildings on the standard map.

Chapter 27 addresses the main wind force resisting system (MWFRS). Chapters 28 through 30 address components and cladding (C&C). Garage doors are C&C elements because they are discrete panels that transfer wind load to the structural framing, not part of the continuous force-resisting system.

The C&C method calculates design pressure using:

• Velocity pressure (q), derived from the design wind speed and exposure
• Velocity pressure exposure coefficient (Kz), which adjusts for height and terrain
• Gust factor (G)
• External pressure coefficient (GCp), which depends on the door's zone location on the building

Zones 4 and 5 (field and edge/corner of a wall) have different pressure coefficients. A door near a building corner or in a recessed entry may see higher pressures than a door in the middle of a long wall.

When it applies

ASCE 7-22 Chapters 26 through 30 are referenced by:

• IBC 2024 Section 1609 (commercial buildings)
• IRC 2024 Section R301.2.1.1 (residential buildings with wind design requirements)

The C&C method is the standard approach for calculating the design wind pressure that a specific garage door must resist at a specific location.

In Colorado, SEAC (Structural Engineers Association of Colorado) has published guidance on applying ASCE 7-22 in Colorado Special Wind Regions. The Vult at Denver is 115 mph, Exposure C for most suburban and plains locations.

What this means for you

Design pressure is site-specific. A garage door specification is not complete without knowing the site's Vult, exposure category, building height, and door zone. The C&C calculation produces a specific psf value. The door's tested rating must meet or exceed that value.

Exposure C is the default in Denver. The plains terrain east of Denver and the open suburban character of most Front Range neighborhoods place most sites in Exposure C. Exposure B (more sheltered terrain) requires buildings to be in dense urban areas or heavily treed surroundings.

Higher buildings need higher ratings. The velocity pressure coefficient (Kz) increases with height. A garage door at 15 feet above grade faces a higher design pressure than one at 10 feet, all else equal.

The door must be rated for both positive and negative pressure. The C&C method produces both inward (positive) and outward suction (negative) pressures. Both values matter. The door's tested rating must cover both directions.

G Brothers uses DASMA TDS #155 (Residential and Commercial Wind Load Guides) and coordinates with structural engineers for commercial projects requiring ASCE 7-22 C&C calculations.

Full text and source

ASCE 7-22 is a copyrighted standard published by ASCE and available for purchase at asce.org. Wind speed maps and design values based on ASCE 7-22 are available through the ASCE Hazard Tool at https://hazards.atcouncil.org/.

ASCE 7-22 is a voluntary consensus standard made mandatory by the IBC and IRC. The design pressures it produces must be matched by tested door pressure ratings under ANSI/DASMA 108.