What is a filler plate on a commercial door?
A filler plate is a flat steel plate that covers an unused hardware cutout on a commercial door or frame. When hardware is changed, upgraded, or removed, the original prep (the cutout made for the previous hardware) may be left exposed. A filler plate screws into place over that opening, restoring the door’s finished surface and structural integrity.
When do I need a filler plate?
A filler plate is needed any time a hardware change leaves an unused cutout on a commercial door or frame. The most common scenarios include converting from a mortise lock to a cylindrical lock (or vice versa), upgrading to a different lock model that uses a different prep, repurposing a prepped door for a new opening, or removing hardware without installing a replacement.
What is the difference between a mortise filler plate and a cylindrical filler plate?
A mortise filler plate covers the rectangular pocket cut into the door edge for a mortise lock body. A cylindrical filler plate covers the circular bore holes cut through the door face and edge for a cylindrical lever lock or knob lock. Each type is shaped to match the specific cutout geometry of its corresponding lock prep.
Are filler plates required on fire-rated doors?
Yes. On fire-rated door assemblies, every opening in the door must be covered with a listed, fire-rated component to maintain the assembly’s fire rating. An uncovered hardware prep is an opening that can compromise the rating and will fail a fire door inspection under NFPA 80. Filler plates used on fire-rated doors must be listed for the specific rating level: 20-minute, 45-minute, 60-minute, 90-minute, or 3-hour (180-minute).
How do I identify which filler plate I need?
Look at the exposed cutout on the door edge. A rectangular pocket indicates a mortise prep; a circular bore indicates a cylindrical prep. Note the door thickness (typically 1-3/4” for commercial doors), the door material (hollow metal or wood), and the desired finish. CDF’s sales team can identify the correct filler plate from a photo of the exposed prep.
Can I reuse a filler plate from another door?
A filler plate can be reused if it matches the prep type, door thickness, and finish of the new door. However, on fire-rated assemblies, the filler plate must be listed for the specific fire rating of the assembly. Verify compatibility before reusing a filler plate on a different door.
Do filler plates affect door security?
An uncovered hardware prep weakens the door edge and creates a potential security vulnerability. A properly installed filler plate restores the structural continuity of the door edge. For high-security applications, confirm that the filler plate and its fasteners meet the security requirements specified for the opening.
How are filler plates installed?
Filler plates attach with machine screws through pre-drilled holes in the plate. The plate is positioned over the exposed cutout on the door edge or face, aligned with the existing screw holes or new holes drilled to match, and secured with the provided screws. The installed plate sits flush with the surrounding door surface.
