Garage Door System GuideIn a hurricane, the garage door is often the largest and weakest opening on a house. The Building America Solution Center notes that a breached garage door creates a large opening in the building envelope, letting wind raise internal pressure until it pushes out windows, walls, and roofs. That is why garage doors are pressure rated, not just wind-speed rated. This guide explains design pressure, impact rating, and the DASMA, IRC, and Florida code requirements behind the labels.
Why a garage door is a structural component
The garage door is not just a big panel; it is part of the structure that holds the storm out. The Building America Solution Center explains that a breached garage door creates a large breach of the building envelope, and that this breach can allow strong winds to enter the building, where they can increase internal pressures to the point that they push out windows, walls, doors, and roofs.
Because of that risk, the International Residential Code requires garage doors to be tested in accordance with either ASTM E330 or ANSI/DASMA 108. This ties an ordinary residential garage door to a defined structural test rather than to a manufacturer's marketing claim about surviving a given wind.
Pressure, not wind speed, is what gets tested
A door rated for a wind speed alone tells you very little. DASMA explains that wind pressure represents the force exerted by wind, that it is calculated starting with wind speed but is greatly dependent on the structure's configuration and site location, and that it is not enough to say a product will meet a given wind speed. Since doors are tested to pressures, not wind speeds, using pressure lets the manufacturer correctly specify a door.
Design pressure is also two-sided. DASMA notes that in a high wind event both positive and negative pressures are generated: positive pressures try to push the door into the building, and negative pressures try to pull the door out of the building. Which one dominates depends on wind direction and the direction the door faces, which is why wind-rated doors carry both a positive and a negative rating.
Design pressure, design load, and test load
The labels use three related terms, and DASMA draws clear lines between them. Design pressure is the site-specific pressure a door is required to be rated for, design load is the pressure the door is actually rated for, and for a door to be adequate the design load should exceed the design pressure. Test load is the highest pressure a door must sustain during a pressure test such as ANSI/DASMA 108, and is commonly 1.5 times the design load.
DASMA also stresses that the numbers are site-specific. Door size, the least horizontal dimension of the building, the mean roof height, and the door's distance from building corners all affect design wind pressure. For that reason the local building department having authority is the sole and final determiner of the wind load requirements for a given garage door.
Impact rating and windborne debris
In coastal zones, resisting pressure is not enough; the door must also survive flying debris. DASMA explains that impact rated refers to garage doors and glazing that are successfully evaluated according to cyclic and impact test procedures such as those in ANSI/DASMA 115, and advises checking with the local building department to see whether you are in a windborne debris region.
ANSI/DASMA 115 is the standard method for testing sectional garage doors for structural performance under missile impact and cyclic wind pressure, including a large missile impact test. The Building America Solution Center adds that glazing in garage doors must be protected from windborne debris in regions where the design wind velocity is 140 mph or greater, or 130 mph or greater within one mile of the coast.
Florida and the High-Velocity Hurricane Zone
Florida applies the strictest version of these rules. Under the Florida Building Code the door model must carry a Florida Product Approval, an FL number in the state database, or, in Miami-Dade and Broward counties' High-Velocity Hurricane Zone, a Miami-Dade Notice of Acceptance (NOA). The door's design pressure rating must meet or exceed the wind loads calculated for the specific address, exposure, and opening size.
Design wind speeds vary sharply by region. Miami-Dade sits at about 175 mph and the Florida Keys at 170 to 190 mph, while inland Central and North Florida run about 115 to 130 mph. In the High-Velocity Hurricane Zone, all exterior openings must be impact-protected, so a garage door there needs both an adequate pressure rating and impact protection to be approved.
Frequently asked questions
Why are garage doors pressure rated instead of wind-speed rated?
DASMA explains that doors are tested to pressures, not wind speeds, because wind pressure depends heavily on the structure's configuration and site location. A wind speed alone is not enough to correctly specify a door.
What is the difference between design pressure, design load, and test load?
Per DASMA, design pressure is the site-specific pressure a door must be rated for, design load is what the door is actually rated for, and the design load should exceed the design pressure. Test load, commonly 1.5 times the design load, is the highest pressure sustained during testing such as ANSI/DASMA 108.
Do I need an impact rated garage door?
It depends on your location. DASMA advises checking with your local building department to see whether you are in a windborne debris region, and the local building department is the sole and final determiner of wind load requirements for a given door.
What are the rules for garage doors in Florida?
Under the Florida Building Code the door model must carry a Florida Product Approval, or in Miami-Dade and Broward's High-Velocity Hurricane Zone a Miami-Dade Notice of Acceptance. In that zone all exterior openings must be impact-protected, so the door needs both an adequate pressure rating and impact protection.