An exterior door is a system, not just a slab. The main parts include the door slab, frame or jamb, hinges, lock preparation, threshold or sill, weatherstripping and any glazing, sidelights or transom components. Understanding these parts makes replacement, specification and supplier comparison much easier.
Exterior Door Slab
The slab is the movable door itself. It can be wood, fiberglass, steel, aluminum or another construction. When ordering a replacement slab, confirm the actual dimensions, thickness, hinge locations, lock preparation and handing rather than relying only on the nominal door size.
A slab-only replacement can be appropriate when the existing frame is sound and compatible. If the frame is damaged, out of square or unsuitable for the new slab, a complete prehung system may be the better option.
Door Frame or Jamb
The frame surrounds the slab and provides the mounting structure for hinges, strike preparation and weather sealing. Frame material and jamb depth need to match the wall construction and exposure.
For project orders, confirm the finished wall thickness, jamb depth, frame profile, exterior trim and sill configuration. A nominal slab dimension does not tell you the complete frame dimension.
Hinges
Hinges carry the door and control its movement. The number, size and position of hinges depend on door construction, weight and manufacturer requirements. Replacement projects should match existing hinge locations where possible or plan for appropriate frame modifications.
Threshold and Sill
The threshold or sill forms the lower transition between the door and the floor. It plays an important role in water management, weather sealing and accessibility. Its profile should be selected for the installation conditions rather than treated as a cosmetic accessory.
Weatherstripping
Weatherstripping creates a compressible seal between the moving door and the frame. Worn or poorly fitted seals can cause drafts, water intrusion or operating problems even when the door slab itself is in good condition.
Lock, Strike and Hardware Preparation
Exterior doors may be prepared for deadbolts, mortise hardware, multipoint locks or other systems. Confirm the hardware preparation before ordering, particularly for custom or commercial applications.
Glass, Sidelights and Transoms
Glazing can be installed within the door slab or as adjacent sidelights and transoms. These elements should be specified separately because they affect dimensions, appearance, privacy and the overall door system.
Prehung vs Slab-Only Exterior Door
| Option | Best when | Main consideration |
|---|---|---|
| Slab only | Existing frame is compatible | Measurements and hinge/lock locations must match |
| Prehung | Frame needs replacement | Verify rough opening and wall depth |
| Door + sidelights | Wider entry is required | Total unit width matters |
| Double-door system | Wide opening or architectural entry | Meeting stile, hardware and weather sealing matter |
What to Record Before Replacing an Exterior Door
Measure the opening, existing slab, frame depth, threshold and hardware locations. Record handing and swing direction. Photograph the hinge side, strike side, sill and exterior trim. For commercial or repeated project orders, provide a drawing or specification sheet rather than relying on a single measurement.
Bottom Line
The most common exterior-door mistake is comparing slabs while ignoring the rest of the system. Frame, sill, seals and hardware preparation can determine whether a replacement actually fits and performs correctly.
For custom project sourcing, Jusen can provide specifications for aluminum door systems and help define frame, profile, glazing and hardware requirements around the project opening.
