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Residential Design Pressure
Frequently Asked Questions
Exposure
Exposure B
For buildings with a mean roof height of less than or equal to 30 feet (9144 mm), Exposure B shall apply where the ground surface roughness, as defined by Surface Roughness B, prevails in the upwind direction for a distance of at least 1,500 feet (457 m). For buildings with a mean roof height greater than 30 feet (9144 mm), Exposure B shall apply where Surface Roughness B prevails in the upwind direction for a distance of at least 2,600 feet (792 m) or 20 times the height of the building, whichever is greater.
Exposure C
Exposure C shall apply for all cases where Exposure B or D does not apply.
Exposure D
Exposure D shall apply where the ground surface roughness, as defined by Surface Roughness D, prevails in the upwind direction for a distance of at least 5,000 feet (1524 m) or 20 times the height of the building, whichever is greater. Exposure D shall also apply where the ground surface roughness immediately upwind of the site is B or C, and the site is within a distance of 600 feet (183 m) or 20 times the building height, whichever is greater, from an Exposure D condition as defined in the previous sentence.
Risk Category
This is the risk associated with the use of the building.
Buildings and other structures that represent a low hazard to human life in the event of failure, including but not limited to:
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Buildings and other structures except those listed in Risk Categories I, III and IV. | |
Buildings and other structures that represent a substantial hazard to human life in the event of failure, including but not limited to:
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Buildings and other structures designated as essential facilities, including but not limited to:
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How to Determine the Zone 4 or 5 and Explanation for End Wall
To determine the design pressures, you will need to enter the opening size and determine if the opening is in zone 4 or zone 5. The diagram below shows each zone, the dimension “a” is the end wall displayed below, so from the corner and form a distance of “a” it falls under zone 5.
If only a portion of the opening is within this area, assume zone 5.
![Determine zone 4 or 5](https://www.elitepermits.com/wp-content/uploads/2021/11/example-wind-load-calculation-screenshot-9-300x239.png)
Height above the ground
Height from ground level to the middle of the roof height.
![Height above the ground for a house](https://www.elitepermits.com/wp-content/uploads/2021/12/3D-02-First-Floor-RCP-1-1-1024x724.png)
Wind load
Ultimate wind speed, this is the speed design, it is determined by the building code.
![wind speed wind load florida](https://www.elitepermits.com/wp-content/uploads/2021/12/Wind-load.jpg)