What This Article Covers and Who It Helps
This guide is for commercial contractors, facility managers, and architects who are working through a door hardware schedule and have landed on an opening that could take either an exit function or a communicating function mortise latchset. The two modes look nearly identical on a spec sheet, but they control access in fundamentally different ways. Choosing the wrong one before the door is prepped means a costly rework or a failed inspection. This article explains the difference, walks through the decision logic, and points to the project types where each function belongs.
What Is a Communicating Function Mortise Latchset?
A communicating function mortise latchset is designed for openings between two occupied spaces where access needs to be controlled from both sides. The key differentiator: both the inside and outside levers can be locked or unlocked independently, typically by turning a button or thumbturn on each side. Neither side is permanently free-passage, and neither side is permanently locked.
Common plain-language descriptions you may hear from field crews or facility staff:
- "The lock that lets both sides control access"
- "The office-to-office door lock"
- "The connecting room function"
In a communicating setup, a person on either side of the door can choose to lock their own side out without affecting the other side's control. This is the defining characteristic that separates it from exit function.
What Is an Exit Function on a Mortise Latchset?
An exit function mortise latchset keeps the inside lever always free -- pressing or turning the inside lever retracts the latch without a key, without a credential, without any unlocking step. The inside is never locked to egress. The outside is controlled by cylinder or credential.
This behavior is not optional on doors in the path of egress. Model building codes and life safety standards require that occupants be able to exit without specialized knowledge or a key. An exit function latchset built into a mortise lock body satisfies that requirement at openings where a full exit device (push bar) is not required or not specified.
Why the Two Functions Are Easy to Confuse
Both functions ship in a mortise lock body. Both have levers on each side. Both accept a cylinder. On a door schedule, the difference is often buried in a two- or three-character function code that gets misread, misquoted, or defaulted from a prior project's schedule without verification.
Problems that show up in the field when the wrong function is installed:
- An exit-path door receives a communicating latchset: the inside lever can be locked, blocking egress -- a direct code violation on most occupancy types.
- A suite-to-suite connecting door receives an exit function: occupants on one side have no ability to secure the passage, defeating the purpose of the opening entirely.
- A fire door receives the wrong function: the inspector flags it during the annual fire door inspection, and the lock has to come out.
The Decision: Which Function Belongs on Your Opening?
Use exit function when:
- The door is in a required means of egress from any occupied space
- The opening leads from a tenant space, classroom, patient room, or other occupied area toward a corridor or exit stair
- The Authority Having Jurisdiction (AHJ) or the fire door assembly listing requires free egress from the inside
- The occupancy is educational, healthcare, assembly, or any type where life safety code governs occupant release
Use communicating function when:
- The door connects two adjacent occupied suites, offices, or rooms where mutual access control is needed (hotel connecting rooms, medical suite interconnects, executive office suites)
- Neither side is a required exit path -- the opening is supplemental, not primary egress
- The program specifically calls for independent control from both sides
- The architect or end user has documented that egress from each space is provided by a separate door
Healthcare and Hospitality: Where This Decision Comes Up Most Often
In healthcare construction, patient room interconnects between exam rooms or procedure suites are classic communicating-function applications. Both staff sides need to control their own access. These doors are almost never primary egress paths, so the communicating mode is appropriate -- but the design team still needs to confirm egress routing before it ships.
In hotels and extended-stay properties, connecting room doors are the textbook communicating-function opening. Each guest controls their own side. The door between rooms is not a required exit for either unit. Exit function would be the wrong call here because it would prevent either guest from locking their side.
In K-12 schools, the communicating function occasionally appears between classroom pairs designed for team teaching, but the AHJ review is critical -- any door that a student or staff member might reasonably use to exit during an emergency needs exit function, not communicating. When in doubt, exit function is the safer default on educational occupancies.
In commercial office build-outs, suite-to-suite connecting doors in multi-tenant buildings are a frequent source of this spec error. The leasing agent wants occupants on each side to control access; the code compliance team needs to confirm those doors are not primary egress paths. Both conversations need to happen before the hardware schedule ships.
Grade 1 Matters Regardless of Function
Whether the schedule calls for exit or communicating function, commercial openings should be specified at BHMA Grade 1. Grade 1 mortise latchsets are built for the cycle counts that healthcare corridors, school interiors, and hotel suites actually see. Grade 2 and Grade 3 products are not appropriate for commercial applications where long-term performance and low maintenance costs matter.
Preferred lines for Grade 1 mortise hardware in this function category include Accentra (formerly Yale), Sargent, Corbin Russwin, and Hager -- all carried at DoorwaysPlus.com. These lines offer stable parts availability and function consistency across project types, which matters when a facility manager needs to service or replace a unit years after the original installation.
Before the Door Gets Prepped: A Quick Checklist
- Confirm egress routing. Is this door in a required exit path? If yes, exit function only.
- Check the occupancy type. Schools, healthcare, and assembly occupancies have strict egress requirements. Verify with the AHJ if there is any doubt.
- Read the function code on the schedule. Do not assume the prior project's schedule is correct for this opening. Each door type must be independently verified.
- Verify fire door assembly requirements. If the opening is fire-rated, confirm the listed lock function is compatible with the door assembly label.
- Confirm door prep. Mortise latchsets require a specific pocket depth and backset. Verify the door has been prepped -- or will be prepped -- to the manufacturer's template before ordering.
Get the Right Function the First Time
Exit function and communicating function mortise latchsets serve genuinely different purposes. The wrong choice creates a code problem, a security gap, or both. Spec the function based on egress routing and occupancy requirements -- not on what looks familiar from the last project.
DoorwaysPlus.com carries Grade 1 mortise hardware in both exit and communicating configurations from Accentra, Sargent, Corbin Russwin, and Hager. If you are working through a hardware schedule and need help confirming function codes for specific openings, our team can assist before the order ships.