Knox boxes (key lockboxes) and fire department connections (FDCs) are among the most detail-sensitive items on a site plan. Their placement is governed by the fire code and, more importantly, by the local fire marshal's specific requirements, which often go beyond the code minimums. Getting the placement wrong results in a correction notice that can delay your occupancy. Getting it right is a matter of following the rules precisely.

Knox Boxes

A Knox Box is a wall-mounted, high-security key lockbox that holds building access keys and access cards. The fire department holds a master key that opens all Knox Boxes in their jurisdiction, allowing emergency access without breaking down doors. Most fire districts require Knox Boxes on all new commercial, multifamily, and institutional buildings, and on gated communities.

Placement Rules

  • Location: Adjacent to the main entry door, on the lock side (hinge side is wrong — the firefighter needs to reach the Knox Box while standing at the door). For buildings with multiple entries, the Knox Box goes at the entry designated as the fire department access point, which is typically the main entry closest to the fire lane and fire department connection.
  • Height: Typically 48 to 60 inches above finished floor (AFF) to the center of the box. Some districts specify exactly 60 inches. Check the local standard.
  • Mounting surface: Must be mounted on the building wall, not on a post or pole (unless the building wall is not available at the designated entry). The wall must be able to support the box (approximately 10 to 20 pounds).
  • Visibility: The Knox Box must be visible from the fire apparatus access road. It should not be recessed into an alcove or obscured by landscaping, signage, or architectural features.
  • Illumination: An exterior light fixture must illuminate the Knox Box area for nighttime visibility.

What Goes Inside

At minimum, the Knox Box contains keys to all building entry doors, electrical rooms, mechanical rooms, elevator machine rooms, and the fire alarm control panel (FACP). For gated communities, it contains the gate access remote or key. The property owner is responsible for ensuring that the keys inside the Knox Box are current — a Knox Box with the wrong keys is worse than useless because it gives a false sense of access.

Fire Department Connection (FDC)

The FDC is the external connection point where the fire department pumper engine boosts water into the building's fire sprinkler system or standpipe system. It consists of two or more 2.5-inch female swivel fittings (Siamese connection) mounted on the building wall or a freestanding post.

Placement Rules

  • Location: On the street-facing side of the building, within 100 feet of a fire hydrant (per NFPA 13 Section 6.7 and most local fire codes). The 100-foot distance is measured along the path the supply hose would follow, not straight-line.
  • Proximity to fire lane: The FDC must be accessible from the fire apparatus access road. The engine stops at the hydrant to connect supply hose, and a separate hose runs from the engine to the FDC. The FDC should be within 50 to 100 feet of the fire lane.
  • Height: The center of the FDC inlets should be 36 to 48 inches above grade (some districts specify 18 to 36 inches for wall-mounted or 36 to 48 for post-mounted). The inlets must face the approaching fire apparatus.
  • Clearance: A 3-foot clear zone in front of and on both sides of the FDC must be maintained at all times. No landscaping, bollards, signs, or stored materials within this zone.
  • Signage: The FDC must be labeled with a sign indicating the system it serves ("FIRE SPRINKLER," "STANDPIPE," or "COMBINED"). Some districts require the sign to be a specific size and color (typically red with white letters).
  • Visibility: The FDC must be visible from the fire lane. A common correction item is an FDC that is installed on a side wall or recessed into an alcove where the engine company cannot see it from the street.

FDC Type

FDC fittings come in two configurations:

  • Siamese (two 2.5-inch inlets): Standard for most commercial and multifamily buildings
  • Storz (single 4-inch or 5-inch fitting): Increasingly common and often required by modern fire districts because it allows a single large-diameter supply hose connection rather than two smaller hose connections. Check with the AHJ for their preferred or required FDC type.

Coordination Between Knox Box and FDC

Both the Knox Box and FDC should be located in the same general area — at the main fire department access point. This allows the first-arriving engine company to quickly locate the key access, the FDC, and the fire alarm annunciator panel (which is also typically near the main entry). Some fire districts require all three to be within 20 feet of each other.

Common Plan Check Comments

  • "Show Knox Box location on the site plan and floor plan." — Both plans must show it.
  • "FDC must be within 100 feet of a fire hydrant." — Measure the hose lay distance, not straight-line.
  • "FDC placement must be on the street-facing side of the building." — Relocate if it is on a side or rear wall.
  • "Provide 3-foot clearance around the FDC." — Remove any landscaping, signs, or bollards that encroach.
  • "Knox Box height must be 60 inches AFF." — Many districts are specific about this dimension.

Submit to the fire district for review at the same time you submit to the building department. Fire review is a concurrent process, and the earlier you get fire comments, the fewer corrections cascade into the architectural and civil plans.