Fire Ratings & UL Codes: When Smart Locks Can (and Can't) Be Used

Executive Summary

If you touch a Fire Rated Door (the heavy solid door between your garage and house, or any hotel/apartment hallway door), you enter a legal minefield.

Installing a standard smart lock on a fire door can void the fire rating, leading to failed inspections, fines, and potentially voided insurance policies in the event of a fire.

The Golden Rule: You generally cannot modify a verified fire door in the field. You must use hardware that is "UL Listed" for that specific application.

Critical Codes Defined

The "Retrofit" Problem

Most smart locks (August, Level) require you to use the existing deadbolt or bore a hole.

• Problem 1: If you drill a new hole in a fire door, the certification label is void. The core material (gypsum/mineral) is exposed.
• Problem 2: "Surface Mount" locks (like August) use plastic adapters. If the plastic melts, does the latch fail?
  • Result: Most retrofit retrofits are NOT allowed on commercial fire doors unless they have a specific UL listing for it.

3 Rules for Fire Door Compliance

Rule 1: Positive Latching is Mandatory

A fire door must automatically latch when it closes.

• The Conflict: A deadbolt is not a latch. It is manually thrown.
• Requirement: Fire doors almost always require a Passage Lever (which latches) + a Deadbolt, OR a Mortise Lock (where the latch and bolt are one unit). You cannot have only a deadbolt.

Rule 2: No Non-Factory Holing

You cannot drill the door.

• Implication: You must buy a smart lock that fits the exact existing holes (typically standard 2-1/8" bore). If you need to drill a 3rd hole for a sensor? Illegal.

Rule 3: The "Melting Point" Test

The lock knob cannot melt and seal the door shut.

• Why Plastic Fails: Ultra-cheap smart locks use Zinc/Plastic internals. In a 1200°F fire, these fuse.
• The Fix: Look for the "UL" symbol stamped on the latch faceplate.

Safe Bets for Fire Doors

If you are upgrading a Condo or Apartment door (which are Fire Doors):

1. Yale Assure / Schlage Encode: These complete replacements usually carry a 20-minute or 90-minute UL rating verified for residential fire doors.
2. Avoid Retrofits: Do not put a plastic August lock or SwitchBot on a fire door unless you have written approval from the Fire Marshal.

Related Tools

• Lock Grading Decoder: Checks for UL listings.
• Installation Cost Estimator: Warning: Fire door installs cost more due to liability.

Frequently Asked Questions

How do I know if I have a Fire Door?

Look at the hinge edge of the door. There should be a metal tag (The "Label"). It will say "20 Minute" or "90 Minute". Never paint over this label.

Can I install a smart peephole camera on a fire door?

Only if it is UL listed. Removing the existing peephole and putting in a non-rated plastic camera creates a "blowtorch" hole where fire can shoot through.

What about my Garage Entry door?

In single-family homes, the door between House and Garage is a 20-minute fire separation. It must be self-closing (in many states) and positive latching. Ensure your smart lock does not interfere with the self-closing hinges.