What Is The Difference between F13 And F20 Mortise Lock?

In the world of commercial and institutional security, not all locks are created equal. When specifying hardware for a building, architects, contractors, and security professionals rely on standardized ratings to ensure doors and frames can withstand specific types of force. For mortise locks—renowned for their strength and durability—two of the most common and often confused ratings are F13 and F20. While they may sound similar, understanding the distinction is critical for compliance, safety, and performance.

At the heart of this discussion is the UL certified mortise lock. Underwriters Laboratories (UL) is an independent global safety science company that rigorously tests products to verify they meet specific standards. For door hardware, UL Standard 305, "Panic Hardware," and UL 10C, "Positive Pressure Fire Tests of Door Assemblies," outline the requirements for these ratings. An F13 or F20 label on a UL certified mortise lock is your guarantee that the product has passed these demanding tests.

The Foundation: What is a Mortise Lock?

Before diving into the differences, let's establish what a mortise lock is. Unlike a standard cylindrical lockset, a mortise lock is installed within a pocket (the "mortise") cut into the edge of the door. This design allows for a larger, more robust lock mechanism, incorporating a deadbolt, latch bolt, and often additional features like deadbolts and trim. This inherent strength makes the mortise lock the preferred choice for high-traffic commercial entry doors, stairwells, and other demanding applications where security and longevity are paramount.

What is an F20 Rating? The Standard for General Access

The F20 rating is one of the most common certifications for a UL certified mortise lock used in general access applications.

· The "F" stands for "Fire Exit Hardware." This indicates the lock is tested for use on fire-rated door assemblies where panic-safe egress is required.

· The "20" refers to the cycle test. An F20-rated lock must successfully complete 200,000 cycles of testing. A "cycle" involves retracting the latch, simulating the action of someone opening the door.

Key Characteristics of an F20 Mortise Lock:

· Durability: The 200,000-cycle test ensures the lock can withstand the wear and tear of a high-traffic commercial environment without failing.

· Egress Safety: It is designed for safe and immediate egress. Operating the lever (or push pad) from the inside always retracts the latch, allowing for a quick exit.

· Fire Rating Compatibility: It is tested for use on fire-rated doors, ensuring it will not compromise the door's ability to hold back fire for its designated period (e.g., 60 or 90 minutes).

An F20 lock is your go-to solution for main entrances, office corridors, and interior stairwell doors in offices, schools, and hospitals. It balances high-cycle durability with essential life-safety and fire protection.

What is an F13 Rating? The Heavy-Duty Security Specialist

The F13 rating takes the concept of the F20 a step further, focusing on enhanced physical security. It is designed for locations where the door is subject to more abuse or requires a higher level of forcible entry resistance.

· The "F" again stands for "Fire Exit Hardware." Like the F20, it is intended for fire-rated egress doors.

· The "13" signifies a different test standard. While it also undergoes cycle testing, the "13" is derived from ANSI/BHMA A156.13, which outlines the standard for Mortise Locks and Latches. More importantly, an F13-rated lock must pass a more severe security and impact test.

Key Characteristics of an F13 Mortise Lock:

· Superior Forcible Entry Resistance: This is the primary differentiator. F13 locks are subjected to brutal impact tests, including a 150-foot-pound force applied to the lever and a 450-foot-pound force applied to the bolt. This simulates an attacker using a pipe or other tool to try and wrench the lock open.

· Heavy-Duty Construction: To pass these tests, F13 locks are inherently built with stronger internal components, heavier gauge metals, and reinforced trim.

· Durability & Egress: They still provide the same 200,000-cycle durability and panic-safe egress as an F20 lock.

An F13 UL certified mortise lock is specified for high-risk or high-abuse areas. Common applications include:

· Main entrances to buildings in high-crime areas

· Doors leading to sensitive areas (server rooms, pharmacies, cash handling rooms)

· School exterior doors (mandated by certain building codes)

· Doors in correctional facilities or mental health institutions

· Any location where previous lock failures due to forced entry or vandalism have occurred.

F13 vs. F20: A Side-by-Side Comparison

Making the Right Choice for Your Project

Choosing between an F13 and F20 UL certified mortise lock boils down to a risk assessment of the door's location and function.

· Choose an F20 lock for the majority of your commercial interior and standard exterior doors. It provides excellent durability, life-safety egress, and fire rating compliance for typical business environments.

· Choose an F13 lock when security is the paramount concern. If the door is a likely target for forced entry, is in a vulnerable location, or protects high-value assets, the additional investment in an F13-rated lock is not just recommended—it's often required by code or insurance.

Conclusion: It’s More Than Just a Number

The difference between F13 and F20 is not arbitrary; it is a clear, tested, and certified distinction between a highly durable lock and a truly fortified one. Specifying the correct UL certified mortise lock is a non-negotiable aspect of building safety, security, and code compliance. By understanding that F20 covers durability for general use while F13 adds a critical layer of forcible-entry resistance, you can make an informed decision that protects both people and property for years to come. Always consult with a qualified architectural hardware consultant or locksmith to ensure your specifications meet all local building and life safety codes.

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