Mullion Spacing: Smaller Panels Win

Why storefront windows in hurricane zones have more dividers. Closer mullions mean stronger glass systems!

Calculate Your Glazing Loads Now

Get accurate ASCE 7-22 wind load calculations for window mullion spacing on your Broward County project.

Calculate Windows/Doors Loads
3' Spacing
180 MPH Rated
5' Spacing
Needs Thicker Glass
75
PSF Design Pressure
1/2"
Glass Thickness (3')
35%
Cost Savings

Big Glass = Big Problems

Imagine holding a large poster in the wind versus a small card. The poster wants to bend and fly away, but the card stays put. Smaller glass panels work the same way - they're simply stiffer and stronger against wind pressure.

Mullions Create Smaller Panels

Every mullion you add divides the glass into smaller sections. A 6-foot wide opening with one mullion in the middle becomes two 3-foot panels. Each panel only needs to resist half the total wind force, so you can use thinner glass.

The Sweet Spot for Broward County

For most Broward County storefronts, 3 to 4-foot mullion spacing hits the sweet spot. Closer than that adds unnecessary cost in framing. Wider spacing requires expensive thick glass that's heavy and hard to install. Finding the balance saves money!

Frequently Asked Questions

What is a window mullion and why does spacing matter?

A mullion is the vertical or horizontal bar that divides a window into smaller sections. Closer mullion spacing creates smaller glass panels, which are stronger against wind pressure. Think of it like cutting a pizza - smaller slices are easier to handle. In Broward County hurricane zones, tighter mullion spacing lets you use thinner, less expensive glass.

How close should mullions be in Broward County storefronts?

For Broward County storefronts with 180 mph wind speeds, mullion spacing typically ranges from 3 to 5 feet depending on glass thickness and floor height. Corner locations and upper floors may need closer spacing due to higher wind pressures. Your glazing engineer will calculate exact spacing based on design pressure requirements.

Can wider mullion spacing work with thicker glass?

Yes, but there are tradeoffs. Wider spacing means fewer mullions but requires thicker, heavier, more expensive glass. In hurricane zones, the glass must also be impact-rated, which adds more cost. Often, closer mullion spacing with thinner glass is more economical and easier to install than widely-spaced thick panels.

Do horizontal and vertical mullions have different spacing rules?

The principles are the same - smaller panels resist pressure better. However, vertical mullions typically carry more structural load since they span floor-to-floor. Horizontal mullions (transoms) divide the height. The combination determines your effective glass panel size, which engineers use to calculate required glass thickness.

Optimize Your Glazing System

WindLoad.co calculates the ideal mullion spacing for your Broward County project. Balance cost, appearance, and hurricane protection!

Calculate Now