Door latches are mechanical fasteners that hold doors closed without providing the security of a locking mechanism. While often grouped with locks, latches serve a distinct purpose: they keep a door from swinging open under its own weight, wind pressure, or casual contact. Understanding the door knob types and selection process that pairs with your latch choice helps ensure the hardware works as intended. Whether you are installing a new door, replacing old hardware, or designing a custom gate, knowing the different latch styles available will guide you to the right fit for the application.
How Door Latches Work
A door latch uses a movable bolt or spring-loaded mechanism that engages with a strike plate mounted on the door frame. When the door closes, the latch bolt slides into the strike plate opening, holding the door in position. Pulling the handle or turning the knob retracts the bolt, releasing the door. This basic principle applies across nearly all residential and light commercial latch types.
The main distinction between a latch and a lock is that a latch keeps the door closed but does not prevent someone from opening it from the outside. When security is required, a lock cylinder is added to the assembly so that a key must turn to retract the latch. For interior doors, closet doors, and many cabinet applications, the latch alone is adequate. When choosing hardware for exterior applications, consider pairing latches with dedicated locking systems such as those used in garage door systems where both latching and locking functions are integrated.
Internally Mounted Door Latches
Internally mounted latches are installed inside the door itself, with only the handle, knob, or thumb turn visible on the surface. These latches are the most common type used on residential and commercial interior doors. The latch mechanism fits into a drilled hole or mortised recess, and the strike plate mounts to the jamb.
Spring Bolt Latches
The spring bolt latch is the standard mechanism found in most modern interior door knobs. A spring-loaded bolt with a beveled face retracts when the knob is turned and snaps back into place when released.
Key Specifications
| Feature | Standard Residential | Light Commercial |
|---|---|---|
| Bolt throw | 1/2 inch (13 mm) | 3/4 inch (19 mm) |
| Backset | 2-3/8 or 2-3/4 inches | 2-3/4 inches |
| Faceplate type | Round or rectangular | Full lip or rectangular |
| Spring material | Steel | Stainless steel |
| Typical applications | Bedroom, bathroom doors | Office, storeroom doors |
Spring bolt latches are available in two common backsets: 2-3/8 inches for thinner doors and 2-3/4 inches for standard 1-3/8 inch interior doors. When replacing hardware, matching the backset to the existing hole is essential. Proper locating latches on the door edge requires measuring from the edge to the center of the knob bore, a measurement that determines whether standard or offset hardware is needed.
Tubular Latches
Tubular latches are a type of spring bolt latch that uses a cylindrical tube housing the spring and bolt assembly. These are installed by drilling a 1-inch diameter hole through the door face and a smaller 7/8-inch hole into the door edge. Tubular latches are the most common type found in new residential construction because they install quickly with standard drill bits.
Mortise Latches
Mortise latches require cutting a rectangular pocket into the door edge to accept a rectangular case body. These latches are more robust than tubular types and are common in commercial buildings, historic homes, and heavy-duty exterior doors. Mortise latches often incorporate both a latch bolt and a deadbolt in a single case, providing convenience without sacrificing security. The installation process requires precise chiseling or routing, making mortise latches more labor-intensive to install than tubular alternatives.
Externally Mounted Door Latches
Externally mounted latches are attached to the surface of the door and frame rather than embedded inside. These are commonly found on gates, sheds, barn doors, screen doors, and industrial applications where the door thickness or material does not accommodate internal routing.
Barrel Bolt Latches
A barrel bolt consists of a cylindrical rod that slides through a hasp mounted on the door surface and into a receiver on the frame. The rod is typically 3 to 6 inches long with a knurled or T-shaped handle for grip. Barrel bolts are simple, durable, and inexpensive. They do not self-latch, meaning the user must manually slide the bolt into place after closing the door.
Surface Bolt Latches
Surface bolts are similar to barrel bolts but use a flat metal bar instead of a round rod. They are common on French doors, double doors, and cabinets. Surface bolts can be installed vertically on the inactive leaf of a pair of doors, sliding up into a header bracket or down into a floor receiver. This configuration allows one door to remain fixed while the other operates normally.
Latch and Cam Latches
Cam latches are widely used in cabinets, electrical panels, lockers, and RV compartments. A rotating cam engages with a strike plate when the key or handle is turned. The cam shape determines whether the latch requires quarter-turn, half-turn, or full-turn rotation to engage. These latches are compact, surface-mountable, and available in a wide range of materials including zinc, steel, and nylon. Interior door types and installation often incorporate cam latches for cabinet and built-in storage applications.
Specialty Latch Designs for Specific Applications
Magnetic Door Latches
Magnetic latches use a permanent magnet embedded in either the door or the frame to hold the door closed. When the door swings shut, a metal strike plate contacts the magnet, creating a holding force that ranges from 10 to 50 pounds depending on the magnet size. Magnetic latches are silent, have no moving parts to wear out, and are ideal for cabinet doors, French doors, and light-duty interior applications.
Roller Latches
Roller latches use a spring-loaded roller that compresses as the door closes and rolls into a catch on the frame. These are common on closet doors, sliding pocket doors, and cabinet doors where a positive hold is needed without the resistance of a standard spring bolt. The rolling action reduces friction and wear compared to sliding bolts. Roller latches are typically rated for 50,000 to 100,000 cycles depending on material quality.
Privacy Latches
Privacy latches are designed for bathroom and bedroom doors where occasional locking from the inside is needed but keyed access is not required. These latches incorporate a push-button, turn-button, or twist-lock mechanism on the interior side and an emergency release slot on the exterior side. The emergency release is typically a small hole that accepts a flathead screwdriver or paper clip to unlock the door from outside. Privacy latches are not security devices and should not be used where actual access control is needed.
Materials and Finishes for Door Latches
The material and finish of a door latch affect its durability, corrosion resistance, and appearance. The most common base materials are zinc alloy, brass, stainless steel, and steel. Each offers different performance characteristics for indoor versus outdoor use. Door types and materials selection guides recommend stainless steel for coastal or high-humidity environments, while zinc alloy with a plated finish works well for most interior applications.
| Material | Corrosion Resistance | Typical Finishes | Best Use |
|---|---|---|---|
| Zinc alloy | Moderate (requires plating) | Brushed nickel, oil-rubbed bronze | Interior doors |
| Brass | Good | Polished brass, antique brass | Interior and covered exterior |
| Stainless steel | Excellent | Satin, polished | Exterior, marine, coastal |
| Steel | Low (requires coating) | Painted, black oxide | Industrial, low-cost interior |
Popular finishes for residential latches include satin nickel, oil-rubbed bronze, matte black, and polished chrome. These finishes are applied through electroplating, powder coating, or physical vapor deposition. The finish grade is measured by salt spray testing hours; a 200-hour rating is standard for quality interior hardware, while exterior-rated hardware typically requires 500 hours or more.
Selecting the Right Door Latch
Choosing a door latch begins with identifying the door type, its location, and the expected frequency of use. Privacy latches suit bathroom doors, spring bolt latches work for most interior passage doors, and surface bolts fit double-door applications where one leaf stays fixed. Fire door requirements and standards specify that latching hardware must hold the door closed against positive pressure, and many fire-rated assemblies require automatic closing devices in addition to positive latching.
- Frequency of use: High-traffic doors need Grade 1 or Grade 2 hardware rated for 500,000+ cycles. Light-duty interior doors can use Grade 3 hardware rated for 200,000 cycles.
- Door material: Wood doors accept tubular or mortise latches. Metal doors often require specifically designed latch housings. Composite and fiberglass doors typically match wood door preparations.
- Backset alignment: Standard backsets are 2-3/8 or 2-3/4 inches. Offset backsets are available for retrofit applications where the existing bore is not centered.
- ADA compliance: Latch handles must be operable with one closed fist. Lever handles with spring bolt latches meet this requirement while knobs do not.
For commercial and multi-family buildings, coordination between the latch function and the door closer is critical. The latch must engage fully before the closer pulls the door tight, and the strike plate must align with the bolt within 1/16 inch tolerance. Door interlock technology for commercial security systems takes latching further by preventing one door from opening while an adjacent door is still ajar, commonly used in cleanrooms, pharmaceutical facilities, and secure access vestibules.