🔒 Commercial Door Interlocks: What Building Owners and Property Managers Need to Know Before Installation
By Serrurier Shay Locksmith – Commercial Door Security Specialists in Montreal
🚪 Door interlocks are one of the most effective physical security upgrades for commercial buildings, apartment complexes, condominiums, schools, office towers, and controlled-access entrances.
They significantly increase resistance against forced entry methods such as pry bars, screwdrivers, and crowbars while improving the structural integrity of the door opening.
At Serrurier Shay Locksmith, most interlocks we install are for outswing commercial doors. Inswing interlocks are available but are less common and typically require additional planning, measurements, and on-site evaluation before installation.
🔐 What Is a Door Interlock?
A door interlock consists of two matching metal extrusion profiles installed on the door and frame. When the door closes, the profiles lock together, reducing the gap between the door and frame and reinforcing the entire opening.
This design makes it significantly more difficult to force the door open using common break-in tools.
✅ Key Benefits
✔ Increased resistance to pry-bar attacks
✔ Increased resistance to screwdriver attacks
✔ Increased resistance to crowbar attacks
✔ Reduced door gap visibility
✔ Improved structural stability of the door opening
✔ Reduced vibration and rattling
✔ Enhanced appearance and finish
✔ Additional reinforcement for commercial entrances
✔ Improved long-term durability of the opening
🚪 Outswing vs. Inswing Interlocks
🔹 Outswing Interlocks (Most Common)
Typically installed on:
🏢 Commercial buildings
🏬 Retail storefronts
🏠 Apartment buildings
🏫 Schools
🏭 Industrial facilities
🚪 Emergency exits
Outswing doors expose the hinge-side gap externally, making them more vulnerable to prying attacks. Interlocks help protect this critical weak point.
👉 Most interlocks installed by Serrurier Shay Locksmith are outswing systems.
🔹 Inswing Interlocks (Less Common)
Typically used for:
🏠 Residential applications
⚙️ Mechanical rooms
🔧 Utility rooms
🏢 Specialized commercial openings
Inswing installations often require additional evaluation due to trim depth, hardware interference, wall clearance, and access control components.
⚙️ Aluminum vs. Steel Interlocks
🔩 Aluminum Interlocks
✔ Lightweight
✔ Reduced stress on hinges
✔ Less load on door closers
✔ Easier installation handling
🛡 Steel Interlocks
✔ Maximum strength and rigidity
✔ Higher resistance to physical attack
✔ Ideal for high-risk or high-traffic openings
⚠ Steel interlocks add weight to the door assembly and may impact hinge wear, door closer performance, and electric strike alignment over time.
🎨 Available Colors
Most aluminum interlocks are available in:
⚪ White
⚫ Black
🟤 Brown
⚙ Silver / Aluminum finish
📏 Standard Sizes
Common stock lengths include:
📏 82 inches
📏 95 inches
These sizes cover most standard commercial door openings.
📦 Special Order: 107-Inch Interlocks
For oversized commercial doors:
⚠ 107-inch interlocks are typically special order only
⚠ Usually available in steel only
⚠ Aluminum versions are generally not recommended at this length due to bending, warping, or shipping damage risks
⏳ Typical lead time: 6 to 16 weeks
Lead time depends on:
• Manufacturer availability
• Color selection
• Production schedule
• Freight conditions
• Seasonal demand
👉 Early ordering is strongly recommended for construction projects with deadlines.
🔍 Proper Selection Is Critical
Choosing the correct interlock is not based only on size.
Every opening must be evaluated for:
✔ Frame depth
✔ Lock location
✔ Electric strike position
✔ Door clearance
✔ Existing hardware
✔ Access control systems
Incorrect selection can interfere with door operation or electronic locking systems.
🔧 Hardware Modifications May Be Required
In many installations, existing hardware must be temporarily removed, including:
🔑 Cylinders
🚪 Lever handles
🛠 Mortise lock trims
🔒 Deadlatches
📋 Escutcheons
🚨 Exit devices
📲 Access control components
After installation, all hardware is reinstalled, adjusted, and tested for proper operation.
⚡ Electric Strike Considerations
When electric strikes are present, careful alignment is essential:
✔ Latch engagement
✔ Strike clearance
✔ Keeper movement
✔ Access control compatibility
✔ Frame reinforcement requirements
Any protruding brackets or reinforcement plates may need adjustment before installation.
🚪 Double Door Applications
On double-door openings, interlocks may affect the opposing door due to reduced clearance.
Possible impacts include:
🚪 Handle interference
🚪 Exit device obstruction
📋 Escutcheon conflicts
⚠ In some cases, hardware modification or replacement may be required.
🛡️ Security Limitations
Interlocks significantly improve resistance against forced entry, but they do not make a door “break-in proof.”
Overall security depends on:
🔒 Lock quality
⚡ Electric strike strength
🚪 Door condition
🏗 Frame condition
🔩 Hinges
📲 Access control system
🪟 Glass and glazing
💪 Best Applications
Interlocks provide the highest level of protection when installed on:
✔ Reinforced steel doors
✔ Commercial deadbolt systems
✔ Mechanical locking systems
✔ High-security entrances
✔ Exit doors with upgraded hardware
These configurations offer stronger overall resistance than systems relying only on electric strikes.
👨🔧 Professional Assessment Recommended
Every door opening is different.
Before installation, we evaluate:
🔍 Door alignment
🔍 Frame condition
🔍 Hardware compatibility
🔍 Electric strike function
🔍 Access control integration
🔍 Clearance and spacing
A proper evaluation helps prevent installation issues and ensures long-term reliability.
⚠️ Disclaimer
This article is for informational purposes only.
Serrurier Shay Locksmith is not affiliated, associated, endorsed, authorized, or sponsored by Frontline Defense Interlock or any of its manufacturers or distributors.
No security product can guarantee complete protection against break-ins, theft, vandalism, or unauthorized entry.
By proceeding with installation, the client acknowledges that all security systems have limitations based on hardware condition, installation quality, and environmental factors.
📞 Contact Serrurier Shay Locksmith
🔒 Commercial • Residential • Industrial Locksmith Services
📧 info@serruriermontreal.com
📞 514-836-9097
🕒 Emergency Service Available Lockouts
📍 Montreal • Laval • West Island • South Shore • Côte-Saint-Luc • NDG • Ville Saint-Laurent • Pointe-Claire • Dorval and surrounding areas
