We use cookies to give you the best possible online experience. If you continue, we'll assume you are happy for your web browser to receive all cookies from our website. See our cookie policy for more information on cookies and how to manage them.

Knowledge store

For tips, tools and guidance on all things risk management, just search for a topic you’re interested in or use the below pods.

Knowledge store general enquiry form
Submit enquiry

Perimeter Security [Hardfacts]


The perimeter of premises can be regarded as any defined boundary between property (land or buildings) in one ownership and property that belongs to others, and in terms of security especially that which is accessible to the public.

According to its nature, the perimeter of premises should always be considered as a first line of defence against trespassers or intruders.

This Hardfacts outlines various aspects of perimeter security at commercial premises.

Basic Principles

Perimeter defences may be considered in terms of psychological, physical or electronic barriers, with each having to be overcome by any intruder intent on gaining further access.

The likely effectiveness of any perimeter defence can be assessed by considering a set of factors termed the four ‘D's, i.e. does it:

  • Deter entry/theft
  • Defend against entry/theft
  • Detect entry
  • Delay entry/removal of property

Good security often requires a complementary set of security measures to be put in place, and, where they exist, ideally at each of three potential perimeters.

Potential Perimeters

Depending upon the nature of the premises, three potential perimeters may exist, namely:

  • The Land Perimeter
  • The Building Perimeter
  • Inner Building Perimeter

By looking at each of these in turn and considering the effectiveness of your current security measures, you should be able to spot any weaknesses, and from that identify areas for improvement. The remainder of this ‘Hardfacts' provides some examples of how this might be done.

Land Perimeter

Where buildings are surrounded fully or partly by their own land, steps should be taken to mark and/or defend the land perimeter, so consider:

Psychological Measures

Marking of the perimeter can act as a barrier to entry. Marking may comprise natural or artificial landscaping, warning signs, permanent or sensor activated lighting, posts or changed type/colour of paving.

A manned presence, e.g. security guards, at gates and other entrances can be an effective check on unauthorised entry. The criteria for selecting a guarding company should include staff holding appropriate Security Industry Authority (SIA) licences, adhering to recognised training and operating procedures (e.g. those set out in BS 7499 - Code of Practice for Static Site Guarding and Mobile Patrol Services), having suitable insurance and being subject to a strict regime of external inspection/site audits.

Although companies who hold SIA Approved Contractor Scheme (ACS) status will have suitably licensed and trained staff, National Security Inspectorate (NSI) or Security Systems and Alarms Inspection board (SSAIB) listing is the best indicator of complete compliance with all of the above recommendations.

Physical Measures

Subject to any planning or design considerations, the erection of a physical boundary of sufficient size and strength to hinder entry is often desirable, e.g. a wall or fence.

Walls and fences will typically comprise:

  • Masonry walls
  • Metal palisade/railings
  • Metal weld mesh/chain link
  • Timber fences
    Note. In general, chain link and timber fences only provide a low level of protection.

Gates should be:

  • Of similar size/strength as the wall/fence
  • Secured by robust locks/padlocks
  • Protected against lifting/removal, e.g. by having a top hinge pin inverted or hinge tops welded over
  • Designed to prevent people crawling underneath them

Walls, fences and gates can often usefully be enhanced by topping them with barbed/razor wire; but if doing so suitable steps should be taken to help discharge the duty of care owed to third parties under various Occupiers Liability Acts. In basic terms this means that any such enhancement will require that the potentially hazardous wire not being used as a 'trap'; i.e. it should be visible and indicated by suitable warning signs; and, particularly if it adjoins a public area e.g. highway or path, that the public cannot readily come into accidential contact with it,  i.e. it should not overhang public areas and its lowest point should be at least 2 metres above ground level.

Electronic Measures
A perimeter alarm or electric fence system - see ‘Hardfacts' 3023: Electric Fences for further information, can be used to deter or detect entry. Such systems are of limited effectiveness unless someone on site, e.g. a guard, is able to respond to the system, or the fence system is linked to a remotely monitored intruder alarm, or preferably,  a similar CCTV system, i.e. one able to transmit activations to an Alarm Receiving Centre (ARC).   

‘Hardfacts' 3004 CCTV - Guidelines for Purchasers provides further information.

Building Perimeter

The building perimeter can be considered as the walls, roof and any door, window or other opening. Whilst all can be considered to provide a basic psychological deterrent to entry, in additon consider:

Physical Measures

Walls of traditional masonry provide good security but many modern buildings of light construction, e.g. metal cladding, provide minimal resistance to forced entry and cannot be readily improved. In such cases installing a secondary internal barrier e.g. steel mesh, may sometimes prove practical.

Roofs are often less robust than walls and in such cases steps should be taken to reduce the ease of potential access, e.g. by not storing pallets or large bins by the building and by applying anti-climb paint or barriers to features that may assist climbing, e.g. down pipes. As with walls, weak accessible roofs may be provided with a secondary internal barrier.

Door construction, and thus inherent security, varies widely; but in general a steel or solid hardwood door and frame is best, fitted with robust bolts, locks or padlocks.

Some doors can be improved by fitting an external or internal steel sheet, and most will be improved by fitting a secondary internal or external steel gate or roller shutter.

Removal of outward opening doors, via an attack on hinges, can be hindered by fitting hinge bolts.

Emergency (Fire) exit doors can be problematic; as typically only simple securing devices are fitted, e.g. a paddle or bar operated latch or, a perhaps little more robust, a panic bar with top and bottom shooting bolts. To prevent operation of such devices from outside, any adjacent glazing should be protected against breakage, and timber doors protected against a hole being drilled through them (to access such devices) by fitting them with a suitably sized and fixed internal or external steel sheet.

In high risk situations visible locks, such as chains or padlocks, can be used subject to a suitable risk assessment and, if appropriate, Fire Brigade approval. If doing so, it is essential that a robust management system is in place to ensure locks are removed whenever someone is in the building. 

Detailed advice on this topic is available in a doucment published (as a free download) by The RISCAuthority, see 

Windows also vary in construction. Accessible opening types should at least have a key locking handle/window lock and for all types of accessible window secondary protection can be very useful.

Other openings, e.g. sky/roof lights, ventilation or extraction grills or service hatches should, as appropriate, be treated as doors or windows.

‘Hardfacts' 3017 Door & Window Security and ‘Hardfacts' 3018 Locks and Lock Standards provide further information.

Glazing in doors and windows can be a weak; especially if fitted with (toughened) safety glass to comply with safety regulations, as this glass when broken shatters and drops out of its frame. Laminated glass provides better security, and can enable safety regulations to be met. Alternatively any glazing can be protected by fitting external or internal steel mesh grilles or a steel roller shutter.

‘Hardfacts' 3006: Security Glazing provides further information.

Electronic Measures
An intruder alarm is a common means of deterring or detecting intruders in buildings. Such systems need careful design, especially if a police response is intended.

‘Hardfacts' 3015: Intruder Alarms - Guidelines for Purchasers provides further information.

Inner Building Perimeters

Creating further perimeters inside a building, e.g. a strong inner area or stockroom, etc, can greatly enhance overall security, particularly where the building perimeter cannot be made robust. Such an approach may help deter intruders, but otherwise enables detection of them via a suitable intruder alarm/CCTV system as they gain entry to the building and crucially, before they can gain access to the key assets/areas within.

Key Action Points

  • Assess current perimeter security for adequacy against past or expected threats

  • Clearly establish what you wish further security measures to achieve

  • Seek advice from experienced and competent installers, ideally obtaining several quotations

  • Ask your police crime reduction officer for advice

  • Seek your insurance companies approval or advice over proposed security changes

  • Regular check/maintain security systems or devices, and promptly attend to repairs

Sources of Further Information

Other Aviva Risk Management Solutions Hardfacts in the Property Protection - Security Series, which are available in our ‘Knowledge Store' at

Master Locksmiths Association (MLA). Tel 01327 262255 or see

National Security Inspectorate (NSI) Tel 01628 637512 or see

Security Systems and Alarms Inspection Board (SSAIB). Tel 0191 296 3242 or see

The Security Industry Authority. See

The RISCAuthority. See

British Security Industry Association (BSIA). Tel 0845 389 3889 or see

Next Steps:

  • Source discounted products, available to Aviva insured customers and brokers only, via our Specialist Partners- click here to find out more about the savings you could make
  • View our Tools and Templates
  • Call our Risk Helpline on 0345 366 66 66
  •  Email us at

Please Note
This document contains general information and guidance and is not and should not be relied on as specific advice. The document may not cover every risk, exposure or hazard that may arise and Aviva recommend that you obtain specific advice relevant to the circumstances. AVIVA accepts no responsibility or liability towards any person who may rely upon this document.

Rate this entry

Was this helpful to you?

Risk Management Bulletins