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Home > Support > Hollow Metal Door Technical Support > Seals, Weather & Perimeter Details > Thresholds for Hollow Metal Doors - Commercial Steel Door Selection Guide

Thresholds for Hollow Metal Doors - Commercial Steel Door Selection Guide

Thresholds for Hollow Metal Doors - How to Choose the Correct Commercial Steel Door Threshold

Field Guide for Clearances, ADA Compliance & Fire Rated Openings

Hollow metal doors are the most common commercial door type used in schools, stairwells, offices, mechanical rooms, and exterior service entrances. Unlike wood doors, steel doors cannot be trimmed — which means the threshold height must be selected correctly to maintain door clearance and pass inspection.

Choosing the wrong threshold often causes door dragging, excessive bottom gap, failed fire inspections, or accessibility violations.


Step 1 - Identify the Problem at the Opening

  • Large gap under door - clearance exceeds allowable limits
  • Door dragging - threshold too tall or floor slope
  • Water entering - exterior slab exposure
  • Failed fire inspection - bottom clearance incorrect
  • ADA compliance issue - threshold too high

The threshold does not solve sealing alone — it sets the clearance so the door bottom seal can work correctly.


Step 2 - Understand Steel Door Clearance Rules

Typical allowable bottom clearance (fire doors): up to 3/4"
ADA accessible height: typically 1/2" threshold maximum
Steel doors cannot be cut to adjust height

Because hollow metal doors are fixed in steel frames, the threshold height must be selected to match the existing opening clearance.


Step 3 - Typical Hollow Metal Door Sealing System

A properly functioning commercial opening uses multiple components:

  • Threshold - controls bottom gap
  • Door sweep or automatic door bottom - seals air and water
  • Perimeter gasketing - controls smoke and air movement

Trying to seal a door using only a threshold usually causes the door to bind or fail inspection.


Watch Installation Overview


Choose Threshold by Requirement

ADA Compliant Thresholds - 1/2" accessible openings
Fire Rated Thresholds - inspection compliance
Exterior / Water Protection - weather exposed doors


Select a Threshold Style

Saddle Thresholds - standard commercial replacement
Thresholds With Vinyl Seal - improved sealing performance


Need Exact Replacement Sizes?

Browse stocked sizes and configurations here:
Hollow Metal Door Threshold Parts


Selecting the correct threshold ensures proper door operation, accessibility compliance, and inspection approval.

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Whether you need a quotation or just have a question about a product. Reach out to us today by calling 866-232-5673 or text us questions and photos at 210-275-8966, and one of friendly specialists will be happy to help!

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