Building Security

Like many other performance requirements, the security aspects of a building involve the immediate physiological and psychological well-being of the occupants. The main areas of concern relate to unauthorized entry into a building, vandalism, protection against disasters, lightning, terrorism and the reduction of accidents. The degree of risk associated with a particular building must be established during initial design stages, so that appropriate security measures can be incorporated without hindering the occupants from carrying out their activities. The primary and often most economical defense usually lies in the fabric of a building and therefore involves the use of compatible construction methods (materials and techniques of assembly).

++++ Visual privacy provided by building location and design.

Unauthorized entry

Unauthorized entry can be achieved either visually or physically. Both involve invasion of the private zones of a building. But whereas the former may be no more than inconvenient, the latter often involves violence towards people, and/or damage and theft of furniture, fabrics, machines, personal belongings and livestock. The defense systems involved for the two areas must therefore be considered separately, although they can be resolved together to provide combined security.

Visual privacy can be achieved through external planning arrangements of a building which provide an acceptable degree of remoteness between observer and observed.

When adequate distances for this are not available, or it’s required to augment the remoteness for even greater privacy, the design of a building and its immediate surroundings plays a more important role. The location of the more private zones of a building can be away from the general fields of vision. Alternatively, high perimeter walls, trees and plants, landscaping, projecting wings and outbuildings can be employed as visual barriers.

Although less used today owing to energy conservation requirements, large windows which let in more daylight make room interiors more visible from outside. Cross-lit rooms also reduce privacy levels by silhouetting figures.

Although net curtains or slatted blinds may be considered a satisfactory solution by some people, it should still be possible to obtain the levels of daylight the window was designed to provide and for the occupants to enjoy uncurtained views out of a building without loss of visual privacy.

++++ some of the principles involved when trying to provide reasonable visual privacy between dwellings. They involve the interrelationship between acceptable 'eye-to-eye' remoteness and the use of screening devices above eye level.

As an initial means of defense against unauthorized physical entry, the approach routes to a building should be carefully organized to prevent, or at least limit, the possibility of uncontrolled usage. This principle is always considered during the initial design stages of a building accommodating strongrooms, security stores, prisons, etc.

However, there has been a certain amount of complacency about the planning of a building having less dramatic risks.

This has led to the development of the use of numerous elaborate security measures or costly security patrols, often added to a building as an afterthought in an attempt to justify incomplete initial design investigations. Nevertheless, although entrances can be positioned to provide good, well-lit visibility and control, problems may still arise in a building requiring a high degree of security but where easy access by the public is necessary (banks, hotels, offices, police stations, museums, exhibition halls, etc.). And the final defense against unauthorized entry into a building must rely on some form of locking mechanism.

However, a conflict often arises between providing doors and windows that are secure but which allow the legal occupants of the building to escape unhindered during a fire. A compromise is sometimes required when selecting locks (ironmongery), particularly for doors, although locks are now available which appear to satisfy both criteria.

A similar form of compromise is often required in the design of fitments, which must freely exhibit goods while protecting them from shoplifters.

Methods of construction should augment the initial design considerations which prevent illegal entry. For example, as certain lightweight constructions can be easily dismantled - boards removed from wall-cladding systems or tiles lifted from roofs - care must be taken in their detail design to ensure their use is compatible with the security risk of a building. Windows and doors, normally regarded as a means of giving access, or light and ventilation, should also be considered as a means of admitting a criminal; they must be carefully designed and protected accordingly.

Once the design of a building fabric has provided the maximum amount of security possible, further protection can be given, if necessary, by electronic devices, alarm bells and surveillance by contracted security patrols. At the planning stage it’s advisable to consult the crime prevention officer (CPO) of the local police force for advice about the degrees of risk involved. The building's insurers will also establish their minimum standards for acceptance of risk, and the architect will need to ensure such minimum standards are observed during design and construction.

The experts have produced a guide entitled Security Design which gives an excellent checklist of important considerations under the following headings: assessment of crime risk; layout of site; building design (access from exterior); building design (access - windows and glass); building design (interior); ironmongery; intruder alarm systems; strongrooms and safes; special security planning; building site security (contractor); existing standards on security; references.

The building contractor will also be concerned with security during the construction of a building. Fences and hoardings are necessary to prevent unauthorized entry into the site, which could result in theft of materials, equipment, tools, etc., as well as vandalism. This form of protection will also assist in protecting passers-by, who may other wise be accidentally hurt as a result of certain construction activities. Permanent boundary fences and walls can provide an initial defense against illegal entry into the grounds of a completed building.

Vandalism

Vandalism is a continuing social problem which defies complete resolution, although as for unauthorized entry the design of a building can greatly lessen the likelihood of its occurrence. A building and the adjoining spaces need to provide a means of positive identity to owners and normal users as well as the community in general.

The problem ranges from graffiti on accessible surface finishes to physical damage of a building fabric involving defacement, breakage, or complete destruction by demolition or fire. Graffiti can be avoided if not eliminated by the judicious selection of surface finishes; but physical dam age is a serious problem which may result in a building employing fortress-like construction methods. Everything must be robust and secure from attack where willful damage is likely to occur, so the building's appearance and other performance requirements may suffer. The ordinary use of materials will have to be avoided: glazed areas should be of limited size and reinforced; doors of solid construction; walls of dense robust materials which are not easily ignitable, etc. Under certain conditions, suitably selected materials may require further protection by barriers or screens. Accidental damage can also be avoided by these devices.

To some extent the effects of vandalism can be lessened by a building owner through a design which provides conspicuous observation points, allows damage to be promptly repaired, and litter to be minimized and efficiently cleared.

++++Legal requirements to avoid progressive collapse in tall buildings.

Disasters

As far as the effects on a building are concerned, disasters can take the form of those which happen accidentally and usually through previous ignorance of a phenomenon, or those which could happen as a direct or indirect result of planned actions. An example of an accidental disaster would be a gas explosion causing collapse of a building.

In 1968 this occurred in a newly built, 25-storey block of flats. The explosion in one of the 19th floor flats blew out part of the outer wall, prompting a progressive collapse of all the precast reinforced concrete wall and floor sections to the south-east corner. Four people died in the incident and numerous others were injured. Although a long time ago, this disaster became established as the basis for a complete review of the design and construction procedures used in high-rise buildings of this type. Legislative measures as shown were introduced to avoid any further progressive collapse incidents. Other examples of learning from disasters with previously unknown causes are, unfortunately, numerous. The use of high-alumina cement (HAC) for the load-bearing reinforced concrete members in a building where warm humid atmospheric conditions exist (swimming pools) produces deterioration of the structure and subsequent collapse. Inadequate bearing for pre-stressed reinforced concrete beams causes their collapse. A lack of fire barriers in cavity constructions allows the rapid spread of fire from one part of a building to another. Failures such as these and the Ronan Point disaster can cause serious loss of life and cost enormous sums of money to rectify.

Experience of disasters, together with the continuous research by investigative authorities and testing organizations help to reduce the likelihood of their recurrence. However, there is always need for a designer to proceed cautiously by seeking out maximum information regarding the performance criteria with new products, materials and untried methods of construction.

Specific forms of construction are also available to lessen the effects of natural disasters resulting from earthquakes, floods, hurricanes, etc.

Lightning

The risk of lightning striking a particular building is very low. Therefore, provision for lightning protection is a risk assessment by the building owner or, more realistically, the building insurer. Houses are rarely protected, but larger commercial and industrial premises will be assessed on the basis of their size (height and plan area), contents, purpose, construction materials (exposed metalwork), degree of isolation, likelihood of thunderstorms in the locality and general topography.

A lightning protection system is designed to attract a lightning discharge and direct it to earth through a path of low impedance, thereby limiting the amount of damage that would otherwise occur to the more vulnerable parts of a building. The Code of practice for protection of structures against lightning provides guidance on air termination conductor locations for various applications.

Generally, air terminations comprise a series of conductor strips interconnected to form a grid, with no part of the roof further than 5 m from the grid. Variations are made to suit roof profile, with prominent features such as apexes and spires suitably protected.

Vertical or down conductors are spaced at one per 20 m of building periphery for buildings up to 20 m height and one per 10 m periphery for buildings in excess of 20 m height. Structural steel and metal pipes are bonded to the down conductor. Conductor metals include aluminum, copper and alloys, phosphor-bronze, galvanized steel and stainless steel in 10 mm diameter rods or 20 × 4 mm strips.

Earth terminations are rods driven into the ground to sufficient depth to provide a low electrical resistance.

Maximum test resistance is 10 ohms.

Terrorism

Acts of terrorism or war often involve the use of explosives to cause damage to buildings. For economic reasons there can be few defensive measures taken to avoid complete or even partial destruction of a building constructed using normal techniques. However, when necessary, a building can be specially designed to withstand a certain degree of anticipated damage. Today it seems that the ultimate form of this type of construction is one which must resist the light and heat, blast wave, tremors and fallout from a nuclear explosion. Construction methods can take the form of relatively simple 'do-it-yourself' sealing and containment techniques or those which involve housing large structures almost entirely below ground and which incorporate complicated life-support systems.

Since the events of 11 September 2001, the design and use of high-rise buildings in prime locations has taken on new priorities. By virtue of their prominence and prestige, these buildings are vulnerable to bombing or chemical contamination attack by terrorists. Means for designing-in protection have taken on two perspectives, preservation of the structural integrity of the building (passive) and security and safety of the occupants of a building (active). The following sections consider some aspects of these under separate headings, although there is an element of overlap with some items.

Passive protection

l Enhanced specification for fire proofing and insulating materials.

l Over-specification of fire protection to steelwork.

l Increased thickness of concrete structural walls.

l Use of additives in concrete to improve the performance in hydrocarbon fires.

l Design based around a protective central core.

l Glazing - laminated to avoid splintering.

l Over-designing the peripheral steel or reinforced concrete sub-framing, such that at least two adjacent columns can be lost without the supported substructure failing.

l Strengthening the floor structure and its support inter face to prevent progressive structural collapse.

l Widening of escape stairways beyond Building Regulation and Standard recommendations.

l Fire-escape stairways within a central structural core, in addition to peripheral locations.

l Protection of other escape stairways in a self-contained concrete shell.

l Panic rooms incorporated within a protected central core.

l Ventilation, air-conditioning plant and water tanks sited away from public access. Monitor with CCTV.

l Air intakes located in positions inaccessible to the public.

l Ventilation and air-conditioning systems zoned or separated, instead of traditional centralized systems.

Several independent air movement systems reduce the risk of air contamination of the whole building.

++++ Design factors influencing safety in a building.

Active protection

l Sensors to detect contaminated air located strategically to shut down ventilation and air-conditioning systems and to engage audible and visual alarms.

l Emergency evacuation procedures in place.

l Personal protective equipment (PPE) available to include respirators and protective clothing.

l Monitoring procedures for suspect mail.

l Incidental and subcontracted personnel and support staff security checked and issued with temporary passes.

l Maintenance of a register of personnel entering and leaving the building.

l Fire, smoke and contaminant sensitive alarms installed throughout the building.

l CCTV cameras installed at building access points and at other sensitive areas.

l At entrances in some high-security situations, provision of a personnel screening facility.

Accidents

A building must be designed to ensure that the human activities it accommodates are carried out with the maximum amount of comfort, safety and efficient enjoyment.

It’s also important that the construction of a building is carried out with reasonable comfort, a high degree of safety and, hopefully, enjoyment.

Mention has been made under dimensional suitability (appropriate size) regarding the need to manufacture components to sizes which are sympathetic with building operations and use (see Section 4). However, even appropriately sized components must be used wisely because it’s not uncommon for people either to cause damage or to be damaged, quite accidentally, as a result of ordinary daily activities. Careful consideration must be given to work surface heights in kitchens, offices or workshops, juxtaposition of conflicting activities within confined spaces, suitable clearances around specific activities, etc. The study of the relationship between people and their environment is known as ergonomics and applies physiological and psychological reasoning to anthropometric data.

The design of spaces in and around a building should take into account the appropriately safe features and dimensions for stair-flights, treads, risers and landings;

slopes of ramps; heights and profiles for handrails and guard-rails, etc. Circulation areas must be planned to give efficient movement patterns which avoid mixing of opposing activities. In this respect, special consideration must be given to the problems associated with the circulation of disabled people through a building, and into the various spaces it accommodates. Gas and water services should be separated from electrical services to avoid risks of explosion, fire and electrocution. For the safety of occupants, the opening parts of a window in a wall above ground level should be not less than 800mm above the floor finish. This is the minimum guarding height as indicated in Federal Building Regulations: Protection from falling, collision and impact. Approved Document: Fire safety provides for a maximum height of 1100 mm for purposes of an emergency escape. When ever large areas of clear glass are incorporated in the construction of walls, precautions must be taken to ensure that people are made aware of its presence. Large uninterrupted areas of clear glazing, such as that found between two parts of the same building at the same level or fully glazed doors, must incorporate markings at a height of 1000 and 1500 mm to prevent unaware people colliding with them.

++++Location of safety glass: shaded areas are critical locations for safety glazing; all dimensions are in millimeters.

Accessibility for disabled people

Estimates of the number of disabled people in the -- vary. Figures between 8 percent of the population and 8 million persons provide some scale of the need for building designers, constructors, owners and occupiers to facilitate for the disabled. Legislative measures to ensure that disabled people can access buildings:

Design of buildings and their approaches to meet the needs of disabled people. Code of practice.

The term 'disabled' covers a wide range of incapacities, but it’s the wheelchair-dependent person that is of principal concern to the building designer. A person in a wheelchair can occupy about five times the space needed by an ambulant person. Therefore the following should be incorporated into the construction of new dwellings:

l Building entrance minimum 900 mm wide.

l Firm level access to the building - maximum slope 1 in 20.

l Level (or close to level) principal entrance threshold.

l Entrance door minimum 775 mm clear width.

l Corridors/passageways minimum 750 mm width.

l Stair minimum 900 mm width. Handrail both sides.

l Light switches, power, telephone and aerial sockets at 450-1 200 mm above finished floor level.

l bathroom provision on the entrance or first habitable storey.

Door opens outwards. Clear wheelchair space of 750 mm in front of bathroom with preferably 500 mm each side of the bathroom measured from its centre.

l Flats to have lifts and stairs which enable disabled residents to access other floors (see Building Regulations).

Buildings other than dwellings should have the following provisions:

l Ramped and easy access to buildings. Minimum width 1 200 mm, maximum gradient 1 in 20.

l Tactile pavings (profiled).

l Dropped kerbs.

l Handrails at changes in level.

l Guarding around projections and obstructions.

l Wheelchair maneuverability in entrances.

l Entrance width minimum 800 mm clear space.

l Internal door openings, minimum 750 mm clear space.

l Corridors/passageways minimum 1 200 mm wide.

l Lift facilities--Specification for powered stair lifts: Powered lifting platforms for use by disabled people.

l Stairs minimum 1000 mm wide, rise between landings 1800 mm maximum, step rise maximum 170 mm, step going minimum 250 mm and a handrail each side.

l Wheelchair-access bathroom provision on each floor.

++++7 Screen protection of glazed areas must prevent the passage of a 75 mm sphere, it must be robust, and it must be difficult to climb (vertical rails).

---- Maximum dimensions of annealed glass panels; Annealed glass; Maximum; Maximum

thickness (mm) width (m) height (m)

8 1.10 1.10 10 2.25 2.25 12 4.50 3.00 15 any; any

Safety glazing regulations

The Federal Building Regulations, Approved Document details acceptable standards for glazing materials and protection, including the critical areas which require safety glazing.

The critical locations are defined as follows:

l glass within 800 mm of the finished floor;

l glass within 1 500 mm of the finished floor and contained in a door or adjacent side panel.

Glazing is accepted as safe if it satisfies one of the following definitions:

l It has 'safe break' characteristics determined:

Specification for impact performance requirements for flat safety glass and safety plastics for use in buildings.

l It’s robust or in small panes (see below).

l It’s permanently protected by a screen.

The terms robust and small panes are defined as follows:

Robust--This term applies to inherently strong materials such as polycarbonates. Annealed glass may also be acceptable as defined.

Small panes-- Small panes can be isolated or in small groups separated by glazing bars. The maximum pane width is 250 mm and the maximum pane area is 0.5 m^2.

The nominal thickness should not be less than 6 mm.

Ideas of design safety must be extended to appropriate surface finishes for a specific activity: non-slip floor tiles in swimming pools; non-combustible wall surfaces along fire-escape routes; antistatic finishes in operating theaters.

The use of color can play a very important role in helping to prevent accidents, although it should never be used to justify the safety of a badly designed feature. Apart from adding further dimensions to the shape and form of objects and planes, the addition of color can act as a form of safety language. For example, because red is universally regarded as a warm and arousing color, it can be used effectively to highlight equipment required to be used urgently in the event of danger, e.g. outbreak of fire.

According to the Young-Helmholtz theory,* human beings use a minimum amount of energy when reacting to red, so their response is relatively rapid. Green requires slightly more energy and blue even more. When the safety precautions for certain areas of a building must be emphasized, the use of varying tones of grey in the color scheme should be avoided; they produce slow reactions to danger because they tend to camouflage real conditions due to lack of contrast. The reflectance value of certain colors should similarly be investigated to avoid problems from glare, and also the effects which tungsten or fluorescent lights have on certain colors used to indicate safety precautions.

The use of color as a safety coding device is employed to identify electrical wiring and circuits, hot and cold water services, and various gas supplies, as well as in industrial environments involving machines, steel plants, refineries, cranes and boilers. Some notable designers have used the resulting aesthetic qualities in the production of a building which represents modern hi-tech attitudes towards performance requirements.

Previously we mentioned the need for specialized maintenance equipment when the design of a building makes conventional methods difficult. Whatever form is necessary, every effort must be made to ensure that maintenance personnel, such as window-cleaners, electricians, plumbers, can carry out their work in safety. For example, above the third-story height of a building (and also below where access for ladders is not convenient), windows should be designed so that they can be cleaned and re-glazed from inside, unless there are balconies and special devices incorporated for external maintenance. The maximum human reach is 550 mm for cleaning windows through or across an adjacent opening; side-hung opening windows should have easy-clean hinges which produce a clear gap of 95 mm between frames when the window is open.

* Credited to the English physician Thomas Young (1773-1829) and the German physician Hermann Helmholtz (1821-1894).

Their theories of human color vision defined the color reception in our eyes. It was not until the latter part of the twentieth century that this was proven biologically.

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