Fail-Safe vs Fail-Secure Electric Strike Decision Tree

Why this matters

Fail-safe and fail-secure are not interchangeable. Getting them backwards on a commercial door is the difference between an egress violation (NFPA 101) and a security hole. Fail-safe (unlocked on power loss) is correct for stairwell re-entry and certain life-safety paths. Fail-secure (locked on power loss) is correct for exterior entries, server rooms, and storage. Misspecifying creates an immediate code citation on inspection, or worse, a building where the front door is unlocked after a power outage. This tree gives a defensible spec rule by door function, wiring guidance, and the conversation script for when the customer's intuition disagrees with code.

Symptom presentation - what the customer asks for vs what they need

Customer-facing requests show up in three shapes that need translation:

• "I want it to unlock when the power goes out": typically a stairwell re-entry, an interior conference room, or a misunderstanding of front-door behavior. Confirm whether NFPA egress applies before agreeing.
• "I want it to stay locked no matter what": typically exterior entry, server room, or controlled-access storage. Fail-secure is correct unless this door is on a required egress path.
• "I don't know, the access control company said either way": the access control vendor often defers to the locksmith; the spec is your call to make and document.

The single most common field error is "we'll match the existing strike" when the existing strike is wrong. The audit will not care that you matched the prior installer's mistake.

Quick checks before specifying

Four facts to gather before you choose:

1. Door function: entry, exit, both; primary egress, secondary egress, non-egress.
2. Occupancy classification: business, mercantile, assembly, residential, institutional. Drives NFPA 101 egress rules.
3. Fire rating: rated door requires UL-listed labeled hardware; the fail mode affects label compliance.
4. Backup power: is there UPS or battery backup on the strike circuit? If yes, "fail" is rarer than the spec suggests because power doesn't actually go away.

Isolation tree

1. Is the door on a required egress path per the floor plan (means of egress)? Yes → fail-safe IF the lock is on the egress side; fail-secure only if egress is provided by a panic device that mechanically retracts regardless of strike state. No → continue.
2. Is the door a stairwell door (re-entry stair)? Yes → fail-safe on the corridor side per NFPA 101 stairwell re-entry rules; the door must allow re-entry on power failure. Continue to step 5 for wiring detail.
3. Is the door an exterior main entry? Yes → fail-secure; the door must remain locked on power loss to prevent unauthorized entry. Egress is by interior lever / push pad / panic device, not by strike release. No → continue.
4. Is the door a server room, mechanical room, or controlled-access storage? Yes → fail-secure; access remains restricted on power loss. No → continue.
5. Is the door a fire-rated assembly? Yes → strike must be UL-listed for the door's fire rating; fail mode does not change the rating but the listing does. No → continue.
6. Is the door interior office, conference, or meeting space? Yes → fail-safe is friendlier (door opens on power loss; people can leave); fail-secure is acceptable if interior lever provides egress. Choose per customer preference and document. No → continue.
7. Is the strike on a power-fail rollover circuit (UPS + transfer to fail mode)? Yes → fail mode triggers only on UPS failure, which is rare. Document the rollover policy.

Confirming the diagnosis - the egress check

The single test that resolves the spec: can a person inside the building open this door from the inside to leave, without using a key, electricity, or special knowledge, in a power-out scenario?

• If yes (interior lever, push pad, panic device retracts the latch mechanically), the strike fail mode is about access, not egress. Fail-secure is acceptable.
• If no (egress depends on the strike releasing), the strike fail mode IS the egress path. Fail-safe is required, or the lock design needs to change.

For most commercial doors, the latch is held by the lock body (which has a lever or panic device for free egress) and the strike supplements with electric release for entry. Egress is by lever, not by strike. In that case, fail-secure on the strike is the right answer for entry security with no egress impact.

Confirming - NFPA 101 stairwell re-entry rule

For multi-story buildings (4 stories or more in most jurisdictions, per NFPA 101 7.2.1.5.8), stairwell doors must allow re-entry into the building on the fire floor and the 1st floor at minimum, and some jurisdictions require all floors. The mechanism is typically:

• Stairwell side has a fail-safe strike or fail-safe electrified mortise lock.
• On fire alarm activation OR power loss, the strike releases, allowing re-entry from the stair.
• Corridor side has a passage lever (free entry from corridor) or an entry lever; corridor-to-stair egress is always free.

If the stairwell door is fail-secure on the stair side, a person trapped in the stair after a power loss cannot re-enter. That's a life-safety violation.

Confirming - wiring and power source

Three wiring rules that prevent post-install callbacks:

1. 24 VDC is the standard for most commercial electric strikes; 12 VDC and 24 VAC also common; verify product spec sheet before pulling wire.
2. Inrush current on strike actuation is typically 4 to 8x holding current; size the power supply accordingly. Under-sized supply causes intermittent failure to release.
3. Diode across the strike coil for any DC strike to suppress the back-EMF when the coil de-energizes. Without the diode, the access control board's relay contacts pit and fail within months.

Remediation - retrofit a fail-mode mismatch

If you arrive to find the existing strike is the wrong fail mode:

1. Document with photos and a written report; the property owner's records need to show the corrective action.
2. Order the correct strike (most manufacturers offer the same body in both modes, sometimes as a field-changeable jumper).
3. Replace and test the failure mode by removing power at the supply, not at the strike (a power-out simulation must include the wiring from the supply forward, not just the last 6 in).
4. Verify after re-energizing that normal access control function is preserved.

References

• NFPA 101, Life Safety Code (2021 ed.), Chapter 7 Means of Egress (egress hardware requirements).
• NFPA 101, Section 7.2.1.5.8, Stairwell Door Re-Entry (multi-story re-entry rules).
• IBC 2018 Section 1010.1.9, Door Operations (egress hardware operability).
• UL 1034, Standard for Burglary-Resistant Electric Locking Mechanisms (strike testing standard).
• UL 294, Standard for Access Control System Units (access control listing).
• ANSI/BHMA A156.31, Electric Strikes and Frame Mounted Actuators (commercial electric strike standard).