What Is Communicating Function on a Door Lock?
This article covers the communicating lock function (commonly coded F15) -- what it does, where it belongs, and the specifying decisions that trip up even experienced hardware coordinators. It is useful for architects building opening schedules, facility managers evaluating existing hardware, and commercial contractors quoting institutional or hospitality projects.
Communicating function means both sides of the door require a key to operate the lever or knob. Unlike an office function lock -- where the inside lever is always free -- a communicating lockset keeps the latch retracted from neither side without a key. Turn the cylinder on either face, and the lever operates. Without a key, both sides are locked.
The BHMA/ANSI designation is typically F15 on cylindrical (bored) locksets and has a direct equivalent in the mortise world. You will see it called communicating function, both sides keyed, or simply listed on a hardware schedule as the function code for an adjoining room door.
Where Communicating Function Actually Gets Used
The application context is the clearest way to understand why this function exists. A few common scenarios:
- Hotel and hospitality adjoining rooms: The classic use case. Two guest rooms share a door in the center wall. Each guest controls their own side. Neither can open the other side without a key -- until both turn their cylinders and the door becomes a shared passage.
- Healthcare suite connections: Exam rooms or consultation spaces that need to connect temporarily but remain independently secured when the facility reconfigures workflow.
- Educational facilities: Operable partition doors between classrooms where staff need key control from either room without relying on a single keyed side.
- Offices and tenant spaces: Adjacent suites in multi-tenant buildings where controlled access between spaces is needed during business hours but full separation is required otherwise.
- Retail back-of-house: Connected stockrooms or manager offices sharing a common wall door with controlled access from both sides.
How Communicating Function Differs From Other Lock Functions
Comparing F15 to nearby functions on the schedule prevents misorders and second trips:
- Passage (F01): No locking at all -- latch retracts freely from either side. Wrong for any space requiring controlled separation.
- Office (F05): Outside keyed, inside always free. Appropriate where one side is always the secure side and occupants inside must always be able to exit freely.
- Storeroom (F07/F08): Outside always locked and keyed; inside always free. Common in institutional settings but gives no key control from the inside.
- Communicating (F15): Both sides keyed. Neither side is ever passively free. This is the key distinction -- communicating function does not guarantee free egress from either side in the way office or storeroom functions do.
That last point carries a significant implication for life safety review.
The Egress Question You Must Answer Before Specifying F15
Because communicating function locks both sides, it can restrict egress if placed incorrectly. A communicating lockset should never appear in a required exit path without careful code review. The door between two hotel rooms is not an exit -- the exit is the corridor door on each side. But if a communicating door connects a space to its only means of egress, F15 is the wrong function.
On fire-rated openings, the stakes are higher. A communicating lockset on a labeled door must be fire-listed for that assembly. The function itself does not disqualify the opening, but the hardware must carry the appropriate label, and the installation must be verified against the door and frame listing. Confirm fire listing with the manufacturer before writing F15 into a set on a rated opening.
Cylindrical vs. Mortise: Which Platform Fits the Opening?
Communicating function is available in both cylindrical and mortise configurations, and the choice matters for durability and door prep.
Cylindrical Locksets
A bored cylindrical lockset with F15 function suits light-to-medium duty applications -- hospitality, low-traffic office connections, and residential-adjacent uses. Brands such as Sargent (10X Line and 10 Line), Corbin Russwin (CLX3300 Series), and Accentra (formerly Yale) offer communicating function across their cylindrical lines with Grade 1 ANSI/BHMA certification.
Mortise Locksets
For higher-traffic or more demanding institutional openings -- healthcare suites, school classroom connections, multi-tenant commercial -- a mortise platform delivers greater durability and a more robust latchbolt assembly. Sargent 8200 Series and Corbin Russwin ML2000 Series both support communicating function. The mortise body also accommodates electrified options more cleanly if access control is ever layered in later.
Hardware Schedule and Keying Considerations
Communicating doors frequently create keying complexity that gets missed until the key system is being cut. A few checkpoints:
- Which master key level controls each side? In a hotel, each room side is typically keyed to its own guest keyway or access credential. In a school or healthcare facility, both sides may belong to the same master key level but require separate cylinders.
- Does the opening schedule clearly call out F15 on both sides? A common error is noting the function on the door leaf but not specifying that both cylinders are keyed -- leaving one side with a blank escutcheon or a non-functional trim.
- Are the trim designs coordinated? On a communicating door, both sides carry full lever trim. Confirm lever style, rose or escutcheon type, and finish match the project finish schedule on both faces.
- Closer coordination: If the communicating door is self-closing (required on fire-rated openings), confirm closer clearance does not conflict with trim depth on the push side.
Specifying Communicating Locksets for Your Project
DoorwaysPlus carries communicating function locksets from Sargent, Corbin Russwin, Accentra, PDQ, and Hager across cylindrical and mortise platforms. Whether you are completing a hardware schedule for a new hotel buildout, retrofitting an existing healthcare suite connection, or replacing a worn communicating lockset in a school facility, the right function and platform depend on the opening classification, traffic level, and keying architecture already in place.
If you are unsure whether F15 is the right call for a specific opening -- or need help confirming fire listing on a rated door -- reach out to the team at DoorwaysPlus.com before the hardware set goes to submittal.