Garage Door System GuideThe garage door is often the largest opening on a house, which makes it the weakest point in a high wind event. If it fails, wind enters and can pressurize the whole structure from the inside. The engineering behind wind rated doors is built on pressure, not miles per hour, and it is codified in DASMA technical data and test standards. The facts below come from DASMA Technical Data Sheet 168 and manufacturer literature.
Why pressure, not wind speed, defines the rating
DASMA, the Door and Access Systems Manufacturers Association, is explicit that wind speed alone cannot specify a door. It states that wind speed is not the defining factor in how a component performs in a high wind event; what matters is the amount of velocity pressure the wind produces at that speed, which also depends on building geometry and terrain. That is why DASMA says the industry cannot simply supply a generic 100 MPH door.
Because of this, doors are tested to pressures rather than to wind speeds. DASMA distinguishes design pressure, the site specific pressure a door is required to be rated for, from design load, the pressure a door is actually rated to hold. For a door to be considered adequate, DASMA states the design load should exceed the design pressure at that site. High wind loads also work in two directions at once: DASMA notes that positive pressures push the door into the building while negative pressures try to pull it out.
The test standards: DASMA 108 pressure and DASMA 115 impact
The proof of a wind rating comes from lab testing to recognized standards. DASMA states that the test load, the highest pressure a door must sustain during a pressure test such as ANSI/DASMA 108, is commonly 1.5 times the design load, which builds a margin above the label rating. DASMA also notes that all of the standard test methods for garage doors are based on allowable stress design loads, and that ASCE 7-10 ultimate strength values are converted to those loads by multiplying by 0.6.
In windborne debris regions, pressure alone is not enough. DASMA explains that impact rated refers to doors and glazing successfully evaluated according to cyclic and impact procedures such as those in ANSI/DASMA 115, and advises checking with the local building department to confirm whether a location is in a windborne debris region. DASMA is clear that the building department having authority is the sole and final determiner of the wind load requirements for a given door.
Exposure category and reinforced product options
The same door can face very different loads depending on where it sits. DASMA describes Exposures B, C and D as the common site categories, and notes that a given wind speed produces less pressure in Exposure B, a typical inland subdivision with obstructions, than in the more open Exposures C and D near coastlines and large bodies of water. This is why a coastal door and an inland door of the same size can carry different pressure requirements.
Manufacturers meet elevated ratings with reinforced product lines. Clopay publishes that its WindCode door reinforcement is available for homes in high wind areas across its steel and aluminum collections, and that impact rated glass is available for select full view models. DASMA adds that impact rated glazing does not change the underlying pressure requirement; documents submitted for approval typically must specify the glazing type and the number of glazed sections.