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Components & Cladding (C&C)

Wall Pressure Zones
Zone 4 vs Zone 5

Not all parts of your wall face the same wind pressure. Corners get hit harder! Click the zones below to see the difference in GCp coefficients.

Click Zones to Explore
Zone 5
Zone 4
Zone 5
5
4
GCp Values (10 sq ft)
Zone 4 (Interior)
-1.0
Zone 5 (Corner)
-1.4
Zone 4
Zone 5

Why Corners Get Hit Harder

Imagine blowing on a piece of paper. The middle pushes back smoothly, but the edges flutter wildly. Buildings work the same way!

When wind hits a building corner, it can't just push through - it has to go around. This creates spinning air (vortices) that suck on the corner surfaces with much higher force than the steady push on the middle of the wall.

That's why ASCE 7 defines Zone 5 at corners with higher GCp values - these areas need stronger cladding and connections to resist the extra suction.

Vortex creates suction at corner

a = min(0.1 x W, 0.4 x h)
100 ft wide x 50 ft tall
10 ft zone
50 ft wide x 30 ft tall
5 ft zone

Minimum 3 ft or 4% of least dimension

How Wide is Zone 5?

Zone 5 isn't a fixed width - it depends on your building size. The formula uses "a" which is the smaller of 10% of the building width or 40% of the building height.

For a typical Miami-Dade house that's 50 feet wide and 20 feet tall, Zone 5 extends about 5 feet from each corner. But there's a minimum: Zone 5 can never be less than 3 feet wide.

This means for small structures, a larger percentage of the wall area falls into Zone 5, requiring higher-rated cladding throughout more of the building.

Real Pressure Numbers

In Miami-Dade with 180 mph wind speed, the difference between Zone 4 and Zone 5 is dramatic. For a 10 square foot cladding element:

Zone 4 might see -75 psf negative pressure (suction), while Zone 5 at the same height could experience -105 psf or more - that's 40% higher!

This is why windows and wall panels at building corners often need special reinforcement or different product ratings than those in the middle of the wall.

Zone 4 (Interior Wall)
~75 psf
Suction Pressure
Zone 5 (Corner)
~105 psf
40% Higher Suction

Frequently Asked Questions

What are wall pressure zones in wind load calculations? +
Wall pressure zones define areas of different wind pressure intensity on building walls. Zone 4 covers the interior wall areas while Zone 5 covers corners where wind pressures are higher due to aerodynamic effects like vortex formation.
What is the difference between Zone 4 and Zone 5? +
Zone 5 (corners) experiences higher negative pressures than Zone 4 (interior). For small effective areas around 10 sq ft, Zone 5 GCp can be up to 1.4 versus Zone 4's 1.0, meaning Zone 5 requires 40% stronger cladding attachments.
How wide is Zone 5 on building walls? +
Zone 5 width equals "a" which is the lesser of 10% of the least horizontal dimension or 0.4 times the building height, but not less than 4% of least dimension or 3 feet. For typical Miami-Dade buildings, this creates corner zones 3-10 feet wide.
Why do corners have higher wind loads? +
Wind separates and accelerates around building corners, creating vortices and high suction pressures. This aerodynamic effect causes peak negative pressures 40-50% higher than on flat wall surfaces away from corners.

Get Zone-Specific Wind Loads

Our calculator automatically computes Zone 4 and Zone 5 pressures for all wall surfaces. Get complete component and cladding wind loads for your Miami-Dade project.

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