two sets of double metal doors at end of hallway

Step-by-step procedures for installing commercial hollow metal doors in new construction and retrofit applications.

This guide answers: How to Install Hollow Metal Doors Without Voiding Fire Ratings or Warranties

Receiving and Inspecting Hollow Metal Doors

Proper receiving and inspection procedures prevent installation delays and warranty disputes. Inspect all hollow metal doors and frames upon delivery before signing the bill of lading.

Inspection Checklist

  • Verify packaging is intact with no visible damage to crating or wrapping.
  • Confirm door dimensions match the approved shop drawings. Standard hollow metal doors use nominal sizing, meaning a 3'-0" x 7'-0" nominal door measures approximately 35-3/4" x 83-3/4" actual size, with a standard 3/4" undercut.
  • Inspect for dents, scratches, warping, or damaged edges on all door faces and edges.
  • Verify all hardware preps are correct. Common prep types include 161 cylindrical lock prep and 86 mortise lock prep.
  • Confirm fire labels are present and legible on fire-rated assemblies.
  • Check that hinge locations and quantities match the hardware schedule.

Store doors vertically on their long edge in a dry, covered area. Never stack doors flat or lean them against walls at an angle, as this can cause warping.

Pre-Installation Preparation

Before hanging any hollow metal door, complete the following preparation steps to ensure a proper installation.

Frame Verification

  • Confirm the frame is plumb, level, and square. Use a 6-foot level on both jambs and the head.
  • Measure the frame opening at three points: top, middle, and bottom. The opening should be consistent within 1/16".
  • Verify frame anchoring is complete and grouting (if applicable) has fully cured.

Door Construction

Commercial hollow metal doors are typically constructed from 18 gauge steel with polystyrene or honeycomb core fill. Polystyrene cores provide thermal insulation, while honeycomb cores are standard for most commercial applications. The core material is bonded to the steel faces, creating a rigid, stable assembly.

Hardware Prep Verification

Verify all door preps align with the hardware schedule before installation. A 161 cylindrical prep is the standard cutout for cylindrical lever locks, while an 86 mortise prep provides the deeper pocket required for mortise lock bodies. Mismatched preps are one of the most common causes of installation delays.

Hanging the Door on Hinges

Proper hinge installation is critical for long-term door performance. Most commercial hollow metal doors use three or more full-mortise hinges.

Hinge Installation Sequence

  • Start with the top hinge. Position the hinge leaf in the door prep and insert the top screw loosely.
  • Align the hinge pin vertically and install the remaining screws for the top hinge.
  • With assistance, lift the door and engage the top hinge pin with the frame hinge leaf.
  • Install the bottom hinge pin next, then the middle hinge(s).
  • Tighten all hinge screws after the door is hanging and swinging freely.

For doors over 7'-0" or weighing more than the hinge load rating, use four or more hinges as specified by the hardware manufacturer.

Adjusting Clearances

Proper clearances ensure correct door operation and are required for fire-rated assembly compliance. Clearances are measured between the door edge and the frame rabbet.

Standard Clearance Requirements

  • Hinge jamb clearance: 1/16" to 3/16" (varies by listing for fire-rated doors).
  • Strike jamb clearance: 1/8" nominal.
  • Head clearance: 1/8" nominal.
  • Undercut (bottom clearance): Standard 3/4" undercut from the finished floor unless otherwise specified.

Fire-rated assemblies have specific maximum clearance requirements defined by the listing. The clearances listed by the door and frame manufacturer's fire test listing take precedence over these general guidelines. Always consult the specific fire listing for the assembly being installed.

Hardware Installation Sequence

Follow this sequence when installing hardware on hollow metal doors to avoid rework and ensure proper operation.

  • Step 1: Hinges (already installed during door hanging).
  • Step 2: Lock or latch set. Install the lock body first, then the trim on each side.
  • Step 3: Strike plate in the frame.
  • Step 4: Closer (surface-mounted or concealed, per schedule).
  • Step 5: Exit devices, if applicable.
  • Step 6: Protective trim (kick plates, push/pull plates, armor plates).
  • Step 7: Door stops, holders, or overhead stops.
  • Step 8: Gasketing and smoke seals (for rated assemblies).

Install each component per the manufacturer's template and instructions. For fire-rated assemblies, verify that every hardware component is listed for the specific fire rating of the assembly.

Testing Door Operation

After all hardware is installed, perform a complete operational test of the door assembly.

  • Open and close the door through its full range of motion. The door should swing freely without binding or dragging.
  • Verify the latch engages the strike fully when the door closes.
  • Test the closer for proper closing speed, latching speed, and backcheck (if applicable).
  • Verify the door latches positively without slamming.
  • Check that any exit device operates correctly from the push side.
  • For fire-rated assemblies, confirm the door self-closes and self-latches from any open position.

Document the completed installation with photos of the finished assembly, clearances, and fire labels for project records.

Fire-Rated Assembly Compliance

Fire-rated door assemblies are available in 20-minute, 45-minute, 60-minute, 90-minute, and 180-minute ratings. Every component in a fire-rated assembly — the door, frame, hinges, lock, closer, gasketing, and any other hardware — must be listed and labeled for the specific fire rating of the assembly.

Modifying any component of a fire-rated assembly without authorization from the listing body voids the fire rating. This includes drilling additional holes, cutting new preps, or substituting non-listed hardware. Any field modifications must be performed in accordance with the listing body's procedures and documented accordingly.

How CDF Supports Hollow Metal Door Installation

CDF ships pre-configured hollow metal door assemblies with doors already prepped for the specified hardware. When ordered through CDF's ProBuilder tool, each door arrives with hinge preps, lock preps, closer reinforcements, and any special preps already cut at CDF's fabrication facility. This reduces field labor and eliminates the risk of incorrect field preps voiding fire ratings.

CDF's assemblies include coordinated fire labels when applicable, ensuring all components in the assembly carry matching ratings. Contractors receive a complete package with door, frame, and hardware ready for installation.

A Note on Fire-Rated Assemblies

Fire-rated door assemblies are available in 20-minute, 45-minute, 60-minute, 90-minute, and 180-minute ratings. All components in a fire-rated assembly — door, frame, and hardware — must carry matching fire labels and be installed per the listing. Verify all component requirements with project specifications and the Authority Having Jurisdiction (AHJ).

Configure Your Door Assembly

CDF's ProBuilder tool lets contractors configure complete hollow metal door assemblies — including door, frame, hinges, lock, closer, and all hardware — in a single online session. ProBuilder displays only compatible options for the selected fire rating and application, reducing order errors and ensuring code-compliant assemblies.

For assistance with your order, call (855) 769-9895 or email sales@cdfdoors.com. CDF's sales team is available Monday through Friday, 7:30 AM to 4:30 PM CT.

Frequently Asked Questions

What is the standard clearance between a hollow metal door and frame?

Standard clearances are 1/8" at the head and strike jamb, and 1/16" to 3/16" at the hinge jamb. The undercut is typically 3/4" from the finished floor. Fire-rated assemblies have specific maximum clearance requirements that must comply with the assembly's fire test listing.

What is the difference between 161 and 86 door preps?

A 161 prep is the standard cutout for cylindrical lever locks, which are the most common commercial locksets. An 86 prep provides the deeper mortise pocket required for mortise lock bodies. The correct prep must be specified during ordering, as field-cutting preps on fire-rated doors can void the fire label.

Can I field-modify a fire-rated hollow metal door?

Field modifications to fire-rated doors must be performed in strict accordance with the listing body's field modification procedures. Unauthorized modifications — including drilling, cutting, or adding non-listed hardware — void the fire rating and violate building code. Always consult the specific fire listing before making any changes.

What core types are available in hollow metal doors?

Common core types include polystyrene (for thermal insulation), honeycomb (standard commercial), and mineral fiber or steel stiffened (for higher fire ratings). The core material affects the door's fire rating, sound transmission class (STC), and thermal performance. Core type is determined during configuration based on project requirements.

How should hollow metal doors be stored before installation?

Store hollow metal doors vertically on their long edge in a dry, covered, and ventilated area. Do not stack doors flat or lean them at an angle, as this can cause permanent warping. Keep doors off the ground using blocking, and protect them from moisture, which causes rust on unpainted surfaces.

About CDF Distributors

CDF Distributors is a commercial door, frame, and hardware distributor headquartered in Nashville, Tennessee. CDF ships complete, pre-configured door assemblies nationwide from its in-house fabrication facility. Configure your assembly online at cdfdistributors.com using ProBuilder, or contact CDF at (855) 769-9895 or sales@cdfdoors.com.