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Double door configurations multiply hardware complexity beyond single-door applications through the interaction of inactive leaf latching, active leaf operation, and closing sequence control. Flush bolts secure the inactive leaf at top and bottom into frame strikes, creating a stable center post against which the active leaf latches. Coordinators ensure proper closing sequence, inactive leaf before active leaf, regardless of which door opened first or whether both opened simultaneously.

Improper flush bolt and coordinator specification creates installations that fail fire ratings under NFPA 80, violate accessibility requirements, or simply malfunction during normal operation. Understanding the mechanical interaction between these components prevents costly specification errors. Browse flush bolts and door coordinators to complete your double door specification correctly.

 

Flush Bolt Types and Selection Criteria

Manual Flush Bolts

Manual flush bolts require occupants to manually operate levers extending the top and bottom bolts before closing the active leaf. The lever rotates a cam mechanism driving the bolt rods up and down simultaneously--one lever operation controls both bolts. Manual bolts suit low-traffic applications where the inactive leaf remains closed most of the time, opening only for large item passage or emergency egress.

Standard manual flush bolts install in 1-3/4 inch thick doors with bolts projecting 5/8 to 3/4 inch into frame strikes. The top bolt extends upward into a strike mortised in the frame head, while the bottom bolt projects downward into a floor strike requiring substrate drilling. Installation requires routing a vertical channel in the door edge housing the operating rod connecting top and bottom bolts, typically 1/2 inch wide by full door height.

The manual operation creates operational challenges in high-traffic spaces. Occupants forget to extend bolts before closing the active leaf, leaving the inactive leaf unsecured. The active leaf then has no stable strike point, allowing both doors to rattle and creating security vulnerabilities. Fire-rated pairs require positive latching of both leaves; manual flush bolts that remain unengaged violate this requirement even though the hardware itself carries fire ratings.

Automatic Flush Bolts

Automatic flush bolts use spring-loaded mechanisms that extend the bolts automatically when the inactive leaf closes, eliminating reliance on occupant operation. Opening the inactive leaf retracts both bolts against spring pressure; releasing the door allows springs to drive bolts into their strikes automatically. This self-operation ensures consistent latching regardless of occupant training or attention, making automatic bolts strongly preferred for institutional and high-traffic applications.

Automatic flush bolts cost 150-200 percent more than manual versions but eliminate operational failures from unengaged bolts. The spring mechanisms require more robust construction--heavier gauge materials, reinforced mounting plates, and precision manufacturing ensuring reliable operation through millions of cycles. Quality automatic bolts from manufacturers like Rockwood, Ives, and Trimco deliver 10-15 year service life in institutional settings versus 5-7 years for economy models.

Installation complexity increases slightly compared to manual versions. The spring-loaded mechanism occupies more door edge space, requiring wider routing--typically 5/8 to 3/4 inch versus 1/2 inch for manual. The top bolt housing contains the primary spring mechanism and operating linkage. Some models include damping to prevent bolt slam during extension, reducing noise and impact forces on strikes. Adjustment provisions allow bolt projection tuning to accommodate frame variations without hardware replacement.

 

Strike Installation Requirements

Top Strikes in Frame Head

Top flush bolt strikes mortise into the frame head, requiring 3/4 to 1 inch deep pockets accepting the bolt projection. Strike location must align precisely with the bolt--misalignment exceeding 1/8 inch prevents bolt engagement or causes binding during operation. Hollow metal frames include reinforcement at strike locations from the factory when flush bolt prep is specified on frame schedules. Wood frames require blocking between frame jambs providing solid material for strike installation and holding strength.

Strike depth must accommodate full bolt projection plus 1/8 inch clearance preventing bottoming. Bolts that bottom in strikes do not engage fully, reducing holding strength and creating binding that prevents smooth operation. Strikes include set screws allowing minor positioning adjustments after installation, compensating for door sag or frame settling that shifts alignment over time. These adjustments typically provide 1/4 inch range--adequate for normal building movement but insufficient for severe structural problems.

Floor Strikes and Substrate Preparation

Floor strikes require substrate drilling accepting the bolt projection--typically 3/4 inch diameter by 1-1/2 inch deep. Concrete substrates use core drills creating clean holes without substrate damage beyond the immediate opening. Wood substrates use forstner or spade bits sized for the strike body. Strike bodies include flanges anchoring to the floor surface via screws or adhesive, preventing strike rotation or extraction under bolt operation forces.

Substrate conditions affect floor strike reliability significantly. Concrete must be sound without cracks or spalling; deteriorated concrete requires repair before strike installation or bolts work loose within months. Wood floor systems need solid blocking under strike locations providing adequate fastener purchase--subfloor alone proves insufficient. Raised access floors require special strikes mounting to floor panels, with reinforcement preventing panel damage from bolt impact forces.

Floor strike location must align with the bottom bolt precisely. Use plumb bob from the top bolt when the door is closed to mark the exact floor strike location. Misalignment causes bolts to bind or miss strikes entirely. For complete double door hardware packages, coordinate flush bolts with commercial locksets on the active leaf and door closers ensuring proper operation sequence.

 

Door Coordinator Specifications

Door coordinators mount at the top of double door openings, ensuring the inactive leaf closes before the active leaf regardless of opening sequence. NFPA 80 requires coordinators on fire-rated pairs where both leaves have closers--without coordinators, doors may close simultaneously with the active leaf blocking the inactive leaf from latching, violating fire protection requirements. The coordinator uses mechanical arms or slides temporarily holding the active leaf open while the inactive leaf completes closing.

Coordinator Operating Mechanisms

Overlapping arm coordinators use two arms attached to each door, with the active leaf arm physically catching and holding while the inactive leaf arm completes its travel. Once the inactive leaf latches, the active leaf arm releases allowing final closing. This positive mechanical action provides reliable sequencing but creates visible hardware on the door faces--acceptable in utilitarian applications but aesthetically objectionable in finished spaces.

Track-mounted coordinators use a slide mechanism in an overhead track, with each door connected to a slide that travels in the track during opening and closing. The track includes a sequencing section forcing the active leaf slide to wait while the inactive leaf slide completes travel. This design conceals hardware above the frame head, providing cleaner aesthetics but requiring adequate clearance above the door frame--typically 4-6 inches minimum.

Coordinator selection depends on door weight, closer specifications, and available mounting space. Standard coordinators handle doors up to 200 pounds with standard commercial closers. Heavy-duty models accommodate institutional doors exceeding 250 pounds or high-speed closers used on high-traffic entries. Mounting provisions must align with frame construction--hollow metal frames may need supplemental reinforcement at coordinator mounting locations to handle operational loads.

Fire Rating Requirements and Testing

Coordinators used on fire-rated assemblies must carry UL listings matching or exceeding the door assembly rating. A 90-minute rated pair requires coordinators tested and labeled for minimum 90-minute performance. The listing verifies the coordinator maintains sequencing function through the rated duration under fire conditions--temperatures exceeding 1400 degrees F and positive pressure testing simulating building pressurization during fires.

Installation must follow UL listing requirements precisely. Fastener type, quantity, and placement are specified in the listing conditions; deviations void the rating. Coordinator adjustment must maintain proper sequencing throughout the door operating arc--the inactive leaf must close completely and latch before the active leaf contacts its strike. Test this by opening both leaves fully and releasing simultaneously; the inactive leaf should latch audibly before the active leaf reaches within 2 inches of closing.

 

Installation Sequence and Adjustment

Order of Hardware Installation

Install flush bolts first, establishing the inactive leaf latching points before proceeding with other hardware. Verify bolt operation through multiple cycles, confirming smooth extension and retraction without binding. Install strikes next, using the bolts to verify precise alignment. With flush bolts functional, install the active leaf lockset ensuring proper strike alignment with the now-secured inactive leaf providing stable strike mounting.

Install coordinators last after all door hardware is functional. This sequence allows coordinator adjustment to compensate for actual door closing characteristics--door weight, closer settings, and weatherstripping resistance--rather than theoretical specifications that may not match field conditions. Mount the coordinator per manufacturer instructions, typically requiring 4-6 fasteners into frame head reinforcement or supplemental blocking.

Coordinator Adjustment Procedures

Adjust coordinator timing to ensure the inactive leaf latches before the active leaf begins final closing. Most coordinators include adjustable hold-open positions controlling when the active leaf releases. Start with the manufacturer recommended setting, typically holding the active leaf at 15-20 degrees open while the inactive leaf closes. Test by opening both leaves fully and releasing--the inactive leaf should latch with a distinct click before the active leaf moves past 10 degrees open.

If the active leaf releases too early, increase the hold-open angle. If it releases too late, doors may stay open when both are released from partially open positions. The adjustment window is narrow--2-3 degrees typically--requiring iterative testing to find optimal settings. Document final adjustment positions for future reference during maintenance or coordinator replacement.

 

Troubleshooting Common Double Door Issues

Inactive leaf fails to latch consistently indicates flush bolt misalignment or strike problems. Check bolt projection--bolts must extend minimum 5/8 inch into strikes. Verify strike alignment using the bolt as a guide; misalignment exceeding 1/8 inch requires strike repositioning. Confirm door closer on inactive leaf provides adequate closing force; insufficient force prevents bolt engagement against spring resistance in automatic flush bolts.

Active leaf closes before inactive leaf signals coordinator malfunction or adjustment drift. Re-adjust coordinator hold-open angle per manufacturer procedures. If adjustment does not correct sequencing, inspect coordinator mechanism for damage or wear--bent arms, cracked mounts, or worn pivot points prevent proper operation. Coordinator failure on fire-rated assemblies creates immediate code violations requiring urgent correction before certificate of occupancy issues arise during inspections.

Both leaves rattle when closed despite properly engaged flush bolts indicates active leaf lockset misalignment or inadequate latch projection. Verify latch extends fully into strike--minimum 1/2 inch for commercial locks. Check strike alignment on the inactive leaf edge where active leaf latch engages. Browse panic exit devices for double door applications requiring life safety hardware with integrated flush bolt coordinators.