What Is a Mullion? Commercial Door & Storefront Guide

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A mullion is a vertical or horizontal structural member that divides adjacent door leaves, window units, or storefront panels.

In commercial storefronts, mullions carry wind load and support glazing pockets while defining door and fixed-lite layouts.

Key Takeaways

  • Covers mullion for commercial property managers

What Is a Mullion?

A mullion is a vertical or horizontal structural member that divides adjacent door leaves, window units, or storefront panels.

In commercial storefronts, mullions carry wind load and support glazing pockets while defining door and fixed-lite layouts.

Mullion Types in Commercial Doors

  • Vertical mullions separate double doors or sidelites.
  • Horizontal mullions (transoms) divide door from fixed glass.
  • Corner mullions join storefront runs at building entries.

When Mullions Need Repair

Corrosion at coastal properties, impact damage, or anchor failure can rack the frame and prevent doors from latching.

CWD Services repairs and replaces storefront mullions as part of door and glass service across South Florida.

Need commercial door service in South Florida? Call (888) 560-6655 or request a quote.

Frequently Asked Questions

A mullion is a vertical or horizontal structural member that divides adjacent door leaves, window units, or storefront panels.

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