Threshold

The horizontal component at the bottom of a door frame that bridges the gap between the floor and the door. Thresholds serve multiple functions: they create a weather seal to prevent air infiltration, provide a transition between different flooring materials, and help meet ADA accessibility requirements.

Commercial thresholds are typically made from aluminum, bronze, or stainless steel and range from 1/4″ to 1″ in height. Low-profile or ADA-compliant thresholds must not exceed 1/2″ in height and require beveled edges for wheelchair accessibility. Thermal-break thresholds incorporate an insulating barrier to prevent heat transfer in exterior applications.

Common types include saddle thresholds (raised center), interlocking thresholds (for maximum weather protection), and adjustable thresholds (for uneven floors). Fire-rated door assemblies require specific threshold configurations to maintain their rating. Related terms: door sweep, weatherstripping, gasket. Shop commercial thresholds.