This guide reflects CDF Distributors' standard specifications and field-tested recommendations used by commercial contractors nationwide. The information is provided for specification and selection purposes. Always verify requirements with the Authority Having Jurisdiction (AHJ) for your project location.

For questions or to order a complete door assembly, contact CDF at (855) 769-9895 or sales@cdfdoors.com. Configure your assembly online at ProBuilder: cdfdistributors.com.

About This Guide

What is a drain pan threshold and when is it required?

A drain pan threshold is a threshold assembly that includes a recessed pan or trough beneath the threshold saddle to collect water that passes the primary weather seal. The pan directs water back to the exterior through weep holes. Drain pan thresholds are specified for exterior door openings exposed to wind-driven rain, standing water, or heavy storm conditions where a standard flat threshold would not prevent water infiltration.

What is a thermal break threshold?

A thermal break threshold has a non-conductive material (typically polyamide or PVC) between the interior and exterior portions of the metal extrusion. This interrupts the conductive heat path through the threshold, reducing energy transfer and preventing condensation on interior surfaces. Thermal break thresholds are specified in climate zones with significant heating or cooling loads.

What threshold materials are used for exterior commercial doors?

The three primary materials are aluminum (most common, lightweight, corrosion-resistant), bronze (higher corrosion resistance, specified for coastal and architectural applications), and stainless steel (chemical resistance, high traffic, sanitation requirements). Grade 304 stainless is standard, and grade 316 is used for coastal or chemical-exposure conditions.

How do you waterproof the connection between the threshold and the door frame?

The frame-to-threshold connection is sealed with compatible sealant (silicone or polyurethane) at the jamb and head intersections. The waterproofing membrane from the wall system must extend across the sill area and lap over the drain pan flanges. All sealant joints should use backer rod to maintain proper joint geometry and movement capacity.

What are the ADA requirements for exterior door thresholds?

Under ADA and ICC A117.1, exterior door thresholds are generally limited to 3/4 inch maximum height. Where the threshold height exceeds 1/4 inch, both edges must be beveled. When specifying drain pan or thermal break thresholds, the combined height of all components must stay within this limit.

Can you order a complete exterior door assembly with a waterproof threshold through CDF?

Yes. CDF's ProBuilder tool allows you to configure a complete exterior door assembly including the Pemko threshold, door, frame, weatherstripping, and hardware as a single coordinated package. Contact CDF at (855) 769-9895 for assistance.

Frequently Asked Questions

CDF's ProBuilder tool allows contractors and facility managers to configure complete door, frame, and hardware assemblies online. During configuration, you can select the specific components discussed in this guide and receive an instant quote.

For assistance or to order a complete door assembly, call (855) 769-9895 or email sales@cdfdoors.com. CDF's sales team is available to help you specify the right components for your project.

Configure Your Door Assembly

CDF Distributors provides Pemko exterior thresholds, in addition to several other brands. A full range of exterior threshold types including drain pan thresholds, thermal break thresholds, saddle or ADA and bumper (Lip) thresholds are available.

When configuring a complete exterior door assembly through CDF's ProBuilder tool, specifiers can select the appropriate Pemko threshold type alongside the door, frame, weatherstripping, and hardware for the opening. ProBuilder allows the full exterior assembly — including the threshold, door bottom seal, and perimeter weatherstrip — to be quoted and ordered as a coordinated package.

How CDF Distributors Supplies Exterior Thresholds

Exterior thresholds must comply with accessibility requirements that limit the height of the threshold above the finished floor. Under ADA and ICC A117.1, thresholds at exterior doors are generally limited to 3/4 inch maximum height, with beveled edges on both sides where the threshold height exceeds 1/4 inch.

When specifying drain pan or thermal break thresholds, verify that the combined height of the pan, threshold saddle, and any weather seal components does not exceed the allowable threshold height. Some manufacturers offer low-profile drain pan configurations specifically designed to maintain ADA compliance while providing water management.

ADA Compliance Considerations

The threshold itself is only one component of the waterproof sill assembly. The connection between the threshold, the door frame, the floor slab, and the wall waterproofing system must be sealed and flashed as a coordinated system.

Sealant joints at the threshold perimeter should use materials compatible with the threshold metal and the adjacent substrates. Silicone and polyurethane sealants are the most common choices, selected based on joint movement capacity and substrate adhesion. All sealant joints should be designed as proper two-sided joints with backer rod to ensure correct sealant geometry and movement capability.

• Frame-to-threshold joint: Sealed at the jamb and head connections to prevent water from bypassing the threshold through the frame-to-sill intersection

• Threshold-to-slab joint: Sealed beneath and around the threshold perimeter where it meets the floor construction

• Membrane continuity: The waterproofing membrane from the wall system must extend down and across the sill area, lapping over the drain pan, to create a continuous water barrier

• Backer rod: Required in all sealant joints to establish proper joint depth-to-width ratio and prevent three-sided adhesion, which would restrict joint movement and lead to sealant failure

Sealant and Flashing Integration

The threshold material must withstand the environmental exposure, traffic load, and corrosion conditions specific to the installation. The three primary materials used for exterior commercial thresholds are aluminum, bronze, and stainless steel.

• Aluminum: The most common exterior threshold material. Lightweight, corrosion-resistant in most environments, and available in a wide range of extruded profiles. Mill finish, anodized, and painted options are standard.

• Bronze: Used where higher corrosion resistance or a specific architectural appearance is required. Bronze thresholds resist saltwater exposure and are specified for coastal installations and high-end architectural projects.

• Stainless steel: Specified for environments with chemical exposure, extreme foot traffic, or food-service applications where sanitation is a concern. Grade 304 is standard; grade 316 is used in coastal or chemical-exposure conditions.

Threshold Material Selection

Thermal break thresholds incorporate a non-conductive material (typically a polyamide or PVC thermal barrier) between the interior and exterior portions of the threshold. This interrupts the conductive path through the metal, reducing heat transfer and minimizing condensation on interior surfaces.

Thermal break thresholds are specified in climate zones where heating or cooling loads are significant, and in buildings subject to energy code compliance under ASHRAE 90.1 or IECC. They are particularly important in cold climates where condensation on the interior threshold surface can cause slip hazards and moisture damage to adjacent flooring.

• Construction: Two separate aluminum extrusions connected by a structural thermal break material, maintaining threshold strength while interrupting the thermal path

• U-factor contribution: Thermal break thresholds reduce the overall U-factor of the door assembly, which may be required to meet energy code requirements for the fenestration area

• Condensation resistance: By raising the interior surface temperature above the dew point, thermal break thresholds prevent condensation under normal HVAC operating conditions

Thermal Break Thresholds

Drain pan thresholds (also called pan thresholds or sill pans) are the primary defense against water infiltration at exterior door openings. A drain pan threshold includes a recessed pan or trough beneath the threshold saddle that collects any water passing the primary weather seal and directs it back to the exterior through weep holes or drain slots.

The pan is typically fabricated from extruded aluminum or stainless steel and is flashed into the surrounding waterproofing membrane before the finish threshold is installed on top. Proper installation requires that the pan slope toward the exterior and that all flashing laps are oriented to shed water outward.

• Pan depth: Typically 3/4 inch to 1-1/2 inches deep, sized to the expected water exposure level

• Weep system: Slots or holes at the exterior face of the pan allow collected water to drain to the outside; weep openings must remain unobstructed after construction

• Flashing integration: The pan must tie into the wall waterproofing membrane with proper lap sequencing — the membrane laps over the pan flanges at the jambs and head, and the pan laps over the membrane at the sill

• End dams: Raised edges at the jamb ends of the pan prevent water from running off the sides before it reaches the weep openings

Drain Pan Thresholds

Water infiltration at exterior thresholds is among the most frequent sources of warranty claims and building envelope failures in commercial construction. The following conditions drive the need for specialized threshold specification.

• Wind-driven rain: Horizontal rain under pressure can push water beneath the door bottom and over the threshold, particularly on exposed facades and high-rise entries

• Standing water: Ponding at the sill from storms, snowmelt, or poor site drainage can overwhelm standard thresholds that rely solely on the door sweep for water resistance

• Thermal bridging: Metal thresholds without thermal breaks conduct heat and cold directly through the building envelope, causing condensation on interior surfaces and contributing to energy loss

• Differential movement: Thermal expansion, building settlement, and slab deflection can break sealant joints and open gaps between the threshold and the surrounding construction

Common Exterior Threshold Challenges

The threshold at an exterior commercial door opening is one of the most vulnerable points in the building envelope. It must resist wind-driven rain, standing water from storms or snowmelt, thermal transfer between conditioned and unconditioned spaces, and continuous foot traffic — all while maintaining ADA-compliant height transitions.

Standard interior thresholds are not designed to address these conditions. Exterior thresholds require specific material selections, drainage provisions, thermal break construction, and coordinated sealant and flashing details to prevent water infiltration and structural damage to the surrounding floor assembly.

Why Exterior Thresholds Require Specialized Specification

A specification guide to exterior threshold types, materials, drain pan systems, thermal break construction, and sealant integration for commercial door openings.

This guide answers: How Do You Specify Waterproof Thresholds for Exterior Commercial Door Openings?