Layered security means protecting what matters with several rings of measures, so that no single failure, mistake or clever intruder defeats the whole system. Each layer should deter, detect or delay, and together they must give responders enough time to arrive before an intruder reaches the thing being protected. The layers include physical barriers, electronic systems and, just as importantly, people and procedures.
Start with what you are protecting
Layered design begins with a simple risk assessment. What are the assets: people, cash, stock, equipment, data, controlled substances, the building's operation itself? What threats are realistic for this site: opportunistic theft, organized theft, vandalism, workplace violence, insider misuse? What would each kind of incident cost, and what has already happened here or nearby?
The answers decide where the inner layers go and how strong each layer needs to be. A warehouse full of copper wire and a medical clinic with a small drug supply both need layered security, but the layers look very different.
The rings
Most sites can be thought of as concentric zones. Each boundary between zones is a chance to deter, detect and delay.
- Site perimeter: fences, gates, landscaping, signage and lighting that define the property and discourage casual entry. On higher-risk sites, perimeter detection on the fence line.
- Building envelope: doors, frames, locks, windows and roof hatches, with intrusion contacts and access control at entrances.
- Interior zones: public areas, staff areas and restricted areas, separated by doors with card readers and covered by motion detection after hours.
- Critical assets: server rooms, cash offices, pharmacies, records storage and similar, with the strongest physical protection and their own detection.
Deter, detect, delay, respond
Each layer does one or more of four jobs:
- Deter: make the site look like a poor target. Good lighting, visible cameras, clear signage, maintained fences and an orderly site all signal that someone is paying attention.
- Detect: notice an intrusion as early as possible, with intrusion sensors, perimeter detection, access control alarms such as a door forced or held open, and video analytics.
- Delay: slow the intruder down with barriers: solid doors and frames, good locks, security glazing, cages, safes and locked rooms.
- Respond: get someone to the site who can stop the intrusion, whether a guard, police or staff following a plan.
The test of a layered design is a comparison of times. From the moment of detection, how long would it take an intruder to reach the asset? And how long does it take for the alarm to be assessed, responders to be dispatched and for them to arrive? If the delay after detection is shorter than the response time, the intruder succeeds even though the alarm worked perfectly.
This is why the outer layers matter even when they cannot stop a determined intruder on their own. Detecting at the fence or the envelope, and then putting several locked doors between the intruder and the asset, buys the time the response needs.
How the systems fit together
Electronic systems are most effective when they work as one. Access control knows who should be where; intrusion detection knows when an area is supposed to be empty; video lets an operator see what is happening; lighting makes the video useful and the site less attractive; intercoms let staff talk to visitors before letting them in. Bringing their events together in one place, with clear procedures, turns separate alarms into decisions.
Security and life safety
Security layers must never trap people. Building and fire codes limit how exit doors can be locked, including rules for electromagnetic locks, delayed egress hardware and release of locks when the fire alarm operates. These rules differ in detail between the National Building Code and the codes adopted in each province, so check the code that applies to your building and involve the authority having jurisdiction early. Our guide to access control, door hardware and safe egress explains the principles.
People and procedures
The strongest locks are useless if doors are propped open, and the best cameras are useless if nobody looks at the footage. Layered security includes:
- Clear rules for visitors, contractors and deliveries, and staff who are comfortable applying them.
- Prompt removal of access when people leave or change roles.
- Regular checks that doors close and latch, and alarms for doors held open.
- Written alarm response procedures, including what staff should not do.
- Periodic review of incidents, alarm history and access logs to spot patterns.
- Testing of every system, and drills for the procedures that depend on them.
A worked example
Take a typical case: a single-storey building with offices at the front and a stockroom of high-value tools at the back, on a lot with a rear yard. It has had two break-ins through the rear overhead door in the past year. The existing alarm has one motion detector in the stockroom, and the cameras record to a recorder in the office.
Working through the layers:
- Site: the rear yard is dark and screened from the street by overgrown trees. Better lighting and trimming the landscaping make the yard visible and improve camera images.
- Envelope: the overhead door gets a contact and a second lock, and the rear man door gets a heavier frame. Glass-break detection covers the office windows. Now an attack on the envelope is detected before anyone is inside.
- Interior: the stockroom becomes its own partition with a card reader, so only stock staff can enter, and the motion detector is moved so racking no longer blocks it.
- Asset: the highest-value tools go into a locked cage inside the stockroom, adding delay after detection.
- Response: the alarm instructions are rewritten, cameras covering the yard and doors are linked to the monitoring centre for verification, and the recorder is moved into a locked room.
None of these measures is unusual. Together they move detection out to the envelope and add delay inside, which is what gives the response a chance to work.
Common mistakes
- Buying cameras first. Video is often the first purchase and the last thing that should be designed. Without detection and response, cameras mostly record what happened.
- One strong layer and nothing else. A high-security door on a room with a drop ceiling and drywall partitions can be bypassed.
- Systems that do not talk to each other. An access control alarm at night that nobody sees because it only appears on a workstation in a locked office.
- Ignoring the outside. Poor lighting, overgrown landscaping and unsecured yards invite problems that interior systems then have to deal with. See exterior and security lighting.
How ehZee can help
Our intrusion and security systems service starts by asking what you need to protect and why, surveys the site layer by layer, and designs detection, delay and response measures that work together with access control and video. See also intrusion alarm systems explained.
Common questions
How many layers does a site need?
Enough that the time from first detection to reaching the asset is longer than the response time, and that no single failure leaves the asset unprotected. A low-risk office may need fewer and lighter layers than a pharmacy or a data centre.
Is layered security expensive?
Not necessarily. Some of the most effective layers, such as lighting, landscaping, door hardware maintenance and good procedures, cost relatively little. The design helps spend the budget where it changes the outcome.
Who should be involved in the design?
Facility management, the people who use the space, IT for networked systems, whoever responds to alarms, and your insurer where they have requirements. Involving them early avoids systems that are bypassed because they get in the way.