Related fire door categories: Fire Rated Hollow Metal Doors and Fire Rated Door Pairs.

Are Fire Doors Hollow?

Fire doors are designed to slow the spread of fire and limit heat transfer through rated openings such as corridors, stairwells, and fire barriers. While people often describe commercial steel doors as “hollow metal,” a properly rated fire door is typically filled with a fire-rated core and is tested as part of a listed assembly.

Short answer

Most fire doors are not hollow inside. They usually contain a mineral core or other fire-rated insulating core that helps the door resist heat and flame for a specified time.

What makes a door a fire door?

A door is considered “fire rated” when it is built and tested to a specific standard and carries a permanent label (commonly UL or Intertek/WHI). That label is often found on the hinge edge of the door or the top edge.

• Fire label present - the label must be readable and permanent
• Rated core and construction - built to match the listing
• Compatible rated frame - frame label must match the opening requirements
• Listed hardware - hinges, locks, strikes, closers, and exit devices must be approved for fire door use

Fire door ratings

Fire doors come in different ratings based on the opening and code requirements. Common ratings include:

• 20 minutes
• 45 minutes
• 60 minutes (1 hour)
• 90 minutes (1-1/2 hour)
• 180 minutes (3 hours)

If you are trying to determine the correct rating for your project, see: What Is a 2 Hour Fire Door?.

So why do people call them “hollow”?

The term hollow metal is an industry name for commercial steel doors and frames. Even when a door has a core, the door is still often referred to as “hollow metal” because it is formed from steel faces and built like a commercial steel door. Fire rated models simply use different internal construction and must be labeled.

Common mistake to avoid

A rated door can fail inspection if it is installed with non-rated components. The most common issues include:

• Missing or painted-over fire label
• Non-rated frame used on a rated opening
• Non-listed hardware installed on a fire rated door
• Door not self-closing or not latching correctly

Shop or quote a fire rated door

If you need a fire rated opening, start here:

• Fire Rated Hollow Metal Doors (Single)
• Fire Rated Hollow Metal Door Pairs

Need a custom configuration (size, wall type, vision lite, louver, prep, hardware)? Use our quote tool: Build Your Own Door - Quote Tool.