What is Windload?

Clopay® has developed a unique WindCode® door ID program to help you select the right garage door for your area based on factors like local building code, MPH requirements and mean roof height.

Clopay WindCode® doors are identified by "W" designations on a rating scale from W1 to W9. The higher the "W" rating, the stronger the door.

The International Building Code includes a wind speed map based on data compiled by the National Weather Service (NWS). Wind speed is converted to design pressure and measured in pounds per square foot (PSF) to develop a product rating. On the table below exposure B is used in most situations (urban, suburban, and wooded areas) and Exposure C is generally used in open land with few obstructions or within 1500 feet of the coastline.

WindCode® Door Related Terms


The testing standard used in the garage door industry. Also known as uniform static air pressure testing. This standard was developed by the American Society for Testing and Materials (ASTM) to allow products to be measured in air pressure chambers. ASCE7 Design standard developed by the American Society of Civil Engineers titled "Minimum Design Loads for Buildings and Other Structures". Section 6 of this standard deals with wind loads.


The basis for wind load calculations used in most building codes.

International Building Code

Model building code developed by the International Code Council. Most of the U.S. has adopted this building code (sometimes with slight, locally adopted variations). The wind load provisions in this code specifically call out ASCE7 to be using in wind load calculations.

Design Pressure

The measurement of resistance in both positive and negative directions that a door system must withstand. Design pressures are usually expressed in both positive (PSF+) and negative (PSF-) values. Also known as design load.

Test Pressure

The actual tested wind pressure resistance that a door system will withstand during laboratory testing. Most building officials usually require that the test pressure be equal to 150% of the design pressure. Also known as test load.

3-Second Gust

How wind is measured by the National Weather Service. This data is then compiled into wind maps incorporated into ASCE7 and the International Building Code. The wind speed maps are based on a yearly 2% probability of occurrence (50-year average peak wind).

Mean Roof Height

The height above grade level of the midpoint of the roof. Mean roof height is calculated by averaging the eave and ridge heights, and is used as part of design pressure calculations in both ASCE7 and the International Building Code.

Wind Velocity

The actual measured speed of airflow during a wind event; usually expressed in MPH. Wind velocity is typically measured at 33 feet (10 meters) above ground level at airports and similar open country locations.

WindCode® Doors

The registered name for all Clopay Building Products garage door products designed and tested to comply with wind resistance requirements of local, state, and national building codes. The WindCode® door program includes engineering, marketing and sales efforts designed to assist Clopay's customers understand code issues and to offer the best products for their market.