Jamb & Threshold for Steel Doors

Jamb

The jamb is the vertical framing member that lines the sides (and top, as the head jamb) of a door opening. It provides the structural anchor point for the door panel's hinges and, on the strike side, the locking hardware. Jamb depth is typically matched to the wall assembly thickness so the frame sits flush with the surrounding finish material, whether that's stucco, drywall, or stone.

For steel systems, the jamb is often part of a continuous profile family shared with the rest of the frame, which keeps sightlines consistent across the door and any adjacent fixed glazing. Jamb selection also affects weatherproofing — the jamb typically houses the weatherstripping that seals against the door panel when closed.

Threshold

The threshold is the horizontal component at the base of the door opening, bridging the gap between interior and exterior (or between two interior spaces). It serves several functions:

• Weatherproofing — sheds water away from the interior and works with the door sweep to block air and water infiltration

 

• Structural transition — accommodates the height difference between finished floor materials on either side of the opening

 

• ADA compliance — thresholds for accessible entries are typically limited to a maximum height (commonly referenced as ½ inch beveled, per ADA guidelines) to remain wheelchair-passable

Threshold materials vary — aluminum, bronze, and stainless steel are common for exterior applications due to corrosion resistance, though the specific material is often chosen to complement the door's finish.

Jamb & Threshold Together

Jamb and threshold are specified as a system, not independently — the threshold's height and drainage design need to coordinate with the jamb's weatherstripping and the door panel's bottom sweep to create a continuous weather seal around the full perimeter of the opening. Getting this coordination right is especially important on exterior doors exposed to wind-driven rain, where a mismatch between components is the most common source of water intrusion.