How to read security drawings
Understanding access control, CCTV, intrusion detection, and intercom systems on construction drawings
What Security Drawings Include
Security drawings show the layout, connectivity, and power requirements of a building's access control, surveillance, intrusion detection, and intercom systems. These systems are part of the low-voltage package and must be coordinated with electrical, architectural, and structural drawings.
Unlike power and lighting (which are high-voltage), security systems run on 24VDC or Ethernet, making them part of the low-voltage family alongside data, telecommunications, and fire alarm. They require different conduit types, less clearance, but precise routing to avoid signal degradation.
- Access Control: Card readers, keypads, electric strikes, mag locks, turnstiles, badge credentials
- CCTV/Surveillance: Camera locations, pan-tilt-zoom (PTZ) specifications, network connectivity, video storage systems
- Intrusion Detection: Motion sensors, door and window contacts, glass break detectors, pressure mat sensors
- Intercom/Video Entry: Lobby callstations, apartment units, area monitors, entry stations at doors
- Control Systems: Panels, processors, servers, network equipment locations and connections
Common Security Symbols
Security drawings use standardized symbols to represent equipment. While these can vary by designer, standard symbols include:
Access Control Card Reader
Often shown as a rectangle with a slot symbol or CR notation. Located at doors. Requires power (24VDC) and data connection (RS-485 or Ethernet). Must be on the correct side of the door and coordinated with door hardware.
CCTV Camera
Shown as a small circle, square, or dome symbol with a viewing angle arrow indicating the camera's field of view. PTZ cameras (pan-tilt-zoom) are marked differently. Requires PoE (Power over Ethernet) or dedicated power and network connection.
Motion Sensor/PIR Detector
Often a circle with radiating lines or a motion wave symbol. Must have clear line-of-sight into the space it protects. Placement near vents, heat sources, or moving objects causes false alarms.
Door Contact/Sensor
Shown as a small rectangle or triangle on the door frame and door. When the door opens, the contact signal is sent to the control panel. Used for alarm zones and automation (closing security gates when a door opens).
Electric Strike
Shown on the door hardware schedule and sometimes on the security plan with a bolt symbol. Electronically releases the latch when access is granted. Requires 24VDC power and coordination with the card reader and control panel.
Magnetic Lock (Mag Lock)
Shown on the door frame or in the control diagram. Holds the door closed via electromagnetic force. Requires sustained 24VDC power; if power fails, the door releases. Must be coordinated with door hardware and fire code requirements.
Control Panel/Processor
Shown as a large rectangle in the security room or equipment room. All field devices (readers, cameras, sensors) connect back to the panel. Requires dedicated power, network connectivity, and adequate physical space for mounting and cable terminations.
Intercom/Video Callstation
Shown at lobbies and entry points. Allows visitors to call apartments or offices. Requires network connection and often auxiliary speaker wiring. Must be weatherproofed if at exterior doors.
Reading the Security Riser Diagram
The riser diagram (sometimes called a block diagram) shows how security devices are connected. It's not a schematic in the electrical sense, but rather a logical flow showing:
- Field devices: Card readers, cameras, sensors (shown on the left or bottom)
- Intermediate equipment: Switches, repeaters, splitters, converters
- Control equipment: Panels, processors (shown centrally)
- Network infrastructure: Servers, storage, software platform
- Power supplies: 24VDC supplies, PoE injectors, backup batteries (UPS)
The riser diagram tells you how signals flow. A card reader at the front door connects via RS-485 twisted pair to the access control panel. The panel processes the badge, energizes the electric strike, and logs the event. If the diagram is unclear, field installation will be problematic.
Coordination with Door Hardware and Access
One of the most critical coordination points is between the security plan and the door hardware schedule. The two documents must agree:
Is the reader on the outside (exit side) or inside (entry side)? A reader on the wrong side of the door defeats security and creates a usability nightmare. The hardware schedule should specify reader location as part of the door detail.
Different doors use different hardware. A restroom door might have a badge reader with an electric strike. A secure equipment room might have a mag lock. The hardware schedule lists which doors get what.
Fire-rated doors with mag locks must have battery backup and manual release mechanisms for emergency egress. The hardware schedule must specify these requirements; the security plan must account for the power and release infrastructure.
Misalignment here is a showstopper. Electricians route power to the door location only to find the hardware schedule says a different door needs the strike.
Power Requirements and Circuit Distribution
Security systems are low-voltage (typically 24VDC), but power requirements can be substantial:
PoE (Power over Ethernet)
A single Ethernet cable provides both network connection and 48VDC power to PoE devices (cameras, readers, etc.). Requires an Ethernet switch with PoE support and adequate power budget. A single PoE+ port provides ~30W; multiple PoE devices may require a dedicated PoE switch with high total power budget.
24VDC Power Supplies
For non-PoE devices (magnetic locks, readers, sensors), dedicated 24VDC supplies are required. The specification sheet lists amperage; a typical card reader draws 0.5A, a mag lock draws 1 to 2A. Calculate total load and size the supply accordingly. Undersizing causes voltage drop and device malfunction.
Backup Power (UPS/Battery)
Access control must remain operational during power loss (emergency egress). A UPS (uninterruptible power supply) is required to keep electric strikes and mag locks powered during an outage. Capacity must support the system for at least 15 to 30 minutes (code-dependent). Size the UPS based on total load and required runtime.
Network Connectivity
Security systems require Ethernet connectivity (often separate from building network for security reasons). The plan should show network closet locations, cable routes, and switch placement. Modern systems often use dedicated security networks isolated from IT.
Conduit Pathways and Routing
Security cabling has different requirements than power:
- Separation from power: Twisted-pair low-voltage cable must be separated from 120V/277V power cabling to prevent interference. Minimum 6 inches separation in some specifications, 12 inches in others.
- Conduit type: Security wiring often uses PVC conduit (cheaper) rather than steel for data/comm. Power wiring uses steel rigid conduit (code requirement for mechanical protection in many jurisdictions).
- Cable tray routing: Long runs on architectural drawings show cable tray locations. Security and power typically use separate trays to prevent interference.
- Homerun locations: Each device needs a path back to the control panel. Long runs without intermediate break points are difficult to pull and prone to pulling damage.
Security routing is often an afterthought on architectural drawings. The security contractor expects conduit to be run alongside power, but power routing may not accommodate low-voltage separation. Verify conduit routing with electrical and architectural plans before construction starts.
Common Coordination Issues
These conflicts arise repeatedly:
1. Cameras Pointing at Walls or Obstructed by Structural Elements
A camera location on the security plan is obstructed by a column, beam, or wall on the architectural plan. Result: camera installed in a location where it can't see anything. Verify field of view against architectural sections.
2. Card Readers on Wrong Side of Door
Reader installed on the entry side instead of exit side. Creates a security breach and requires hardware relocation mid-construction. Verify reader location against door schedules.
3. Missing Conduit Homerun from Device to Panel
A reader is shown on the plan but no conduit route is specified. Electricians improvise, running cable through spaces where it gets damaged or where it violates code. Always verify that every device has a defined pathway back to the control panel.
4. Motion Sensors in Locations with Blind Spots
A motion sensor is positioned behind or near a large structure, creating areas not covered by the detector. Intruder can move through the uncovered space. Verify coverage against architectural sections and layouts.
5. Inadequate Power Capacity or Wrong Power Type
24VDC supply sized for 5A but actual load is 8A. Devices malfunction due to voltage drop. Verify power supply sizing against device specifications and total load calculations.
6. No UPS or Backup Power for Door Locks
Mag locks and electric strikes lose power during an outage, preventing emergency egress. Fails fire code inspection. Verify UPS capacity and verify mag locks are on the backup circuit.
What to Look for During Plan Review
When reviewing security drawings, focus on:
All critical access points are protected (main entries, equipment rooms, secure areas)
Camera coverage is complete with no blind spots; verify against architectural sections
Card readers are on the correct side of doors and coordinate with hardware schedule
Power supplies are properly sized and UPS is specified for doors with locks
Conduit routing is defined and separated from power per code
Motion sensor placement provides coverage without blind spots
Network connectivity is shown and security equipment room is adequately sized
Keep exploring
Related references and guides for security and low-voltage coordination.
Understanding power and low-voltage systems on construction drawings
Coordinating data, voice, and network infrastructure
Best practices for reviewing and approving construction documents
Techniques for catching errors and conflicts in drawings
Managing security, data, fire, and telecom systems together
Resolving interdisciplinary conflicts in security and other systems