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Height Matters

Every foot you build higher means more wind pressure. Watch how wind speed increases with height and what it means for your structure.

Drag the slider to grow the building. See wind pressures change in real time.

0 ft
30 ft
60 ft
90 ft
120 ft
160 mph
170 mph
175 mph
180 mph
30 ft
0.85
Kz Factor
66
qz (PSF)
0%
vs 15 ft

How Height Changes Everything

Same 180 mph design wind speed, vastly different pressures based on building height.

🏠

Single Story

15 ft
Kz = 0.85
66 PSF velocity pressure
🏢

Two Story

30 ft
Kz = 0.98
76 PSF velocity pressure
🏣

Commercial

60 ft
Kz = 1.13
88 PSF velocity pressure
🏘

High-Rise

100 ft
Kz = 1.26
98 PSF velocity pressure

Understanding the Kz Factor

The velocity pressure exposure coefficient that determines how much wind your height catches.

Velocity Pressure Formula

qz = 0.00256 x Kz x V2

Where V = basic wind speed (mph)
Result in pounds per square foot (PSF)

Kz = 2.01 x (z/zg)2/α

Where z = height, zg = gradient height
α = terrain exponent

Kz Values - Exposure C

Height (ft) Kz qz @ 180 mph
150.8566 PSF
200.9070 PSF
250.9473 PSF
300.9876 PSF
401.0481 PSF
501.0985 PSF
601.1388 PSF
801.2194 PSF
1001.2698 PSF

Calculating Mean Roof Height

Different roof types have different methods for finding the mean height.

h

Flat Roof

Mean roof height equals eave height. Simplest calculation.

h = eave height
h

Gable Roof

Average of eave and ridge heights.

h = (eave + ridge) / 2
h

Hip Roof

Same as gable - average of eave and peak.

h = (eave + peak) / 2

Multi-Level

Each section calculated separately for local pressures.

h1, h2 per section

Velocity Pressure Calculator

Calculate your design velocity pressure based on height and wind speed.

Kz Factor
0.98
Velocity Pressure (qz)
76
PSF

Based on ASCE 7-22 Table 26.10-1
Kd = 0.85 (directionality) already factored

Common Questions

What is mean roof height in wind engineering?
Mean roof height is the average height from grade to roof. For flat roofs, it's the height to the roof surface. For sloped roofs, it's the average of the eave and ridge heights. This measurement determines which wind speed profile applies to your building and directly affects the velocity pressure coefficient Kz.
Why does building height increase wind loads?
Wind speeds increase with height due to reduced ground friction. At ground level, terrain features slow the wind. At 60 feet, wind is typically 20-30% faster than at 15 feet. Since pressure increases with the square of velocity, small height increases create large pressure increases. A 100-foot building sees nearly 50% higher pressures than a 15-foot building.
What is the Kz factor in wind calculations?
Kz is the velocity pressure exposure coefficient that accounts for how wind speed varies with height and terrain. For Exposure C at 15 feet, Kz is about 0.85. At 60 feet, Kz increases to 1.13. This 33% increase in Kz translates to 33% higher design pressures. The formula comes from boundary layer wind theory.
How is mean roof height calculated for different roof types?
Flat roofs: height from grade to roof surface. Gable roofs: average of eave height and ridge height (eave + ridge) / 2. Hip roofs: same as gable. For multi-level roofs, each section may have different mean heights affecting local pressures. Parapets can also affect the calculation for flat roofs.
What height limits apply in Broward County?
Broward County follows the Florida Building Code with HVHZ provisions. Buildings over 60 feet may require wind tunnel testing. High-rise buildings face additional requirements including enhanced structural connections and potentially different wind load methodology. Local zoning may also limit heights in certain areas.

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Our engineers calculate precise Kz factors and velocity pressures for your exact building height in Broward County.

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Live Calculations
Height
30 ft
Kz Factor
0.98
Pressure
76 PSF