Crime prevention through building design

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Specification Associate, 20, 1, pp. 8-9, 1978-01

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Crime prevention through building design

Johnson, B. M.

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National Research Council of Canada

Conseil national de recherches du Canada

CRIME PREVENTION THROUGH

BUILDING DESIGN

by

B .

M. Johnson

5

Reprinted from Specification Associate . No. 1. JanuaryIFebruary 1978 DBR Paper No. 770 Division of Building Research

Crime Prevention Through Building Design

8. M. Johnson

Mr. Johnson is anxious to receive comments from readers. Please send comments to him at:

Design and Use Section, Division of Building Research, National Research Council of Canada, K I A OR6

Burglary, assault, illegal entry and malicious damage have greatly increased in the past ten years. Recent discussions regarding the importance of building design to this problem were held at the Division of Building Research, National Research Council of Canada. The

participants-specialists in security, building design, building management and sociology~oncluded that relatively simple modifications to building design and the specification of better hardware and construction would greatly reduce crime. This article presents questions raised and

conclusions reached at these discussions.

To provide measures that are sufficient to deter the opportunist without being too elaborate or too expensive, involves an assessment of the risk to the building, its contents and the occupants. Among the factors that determine the likelihood of criminal attack are location of the building, value of contents, and type of

building.' Consideration must be given not only to the costs of building repairs or replacing valuables but also to those resulting from personal injury, trials and the wider social costs of support for convicted criminals and their families. Compared to these, the additional costs of providing adequate protection to most buildings is negligib~e.~

Door Hardware

As elsewhere, housing is by far the most burglarized building type in Canada. By and large, burglary is opportunistic and localized. The greatest increase in burglary rates is in middle income housing. Generally, this housing has been equipped with poor quality doors, windows and locks. According to a U.S. report, 53 per cent of illegal entries were through doors and almost all were gained by

defeating the lock. Many types of locks

are available and several are

recommended by police authorities but few are effective. The mortice

dead-bolt shown in Figure 1 with a 25-mm (1 -in.) throw will withstand most assaults if mounted in a strong door. Other locks tend to be either more expensive or less effective. A bolt with a throw of 15 mm (5/8 in.) is not adequate because it is fairly easy to force the door frame open several millimetres unless tolerances of the door frame are kept to 3 mm (1 /8 in.) or less (a near impossibility). Spring bolts can often be forced open with a plastic charge plate or otherwise

"jimmied." Rim-mounted locks can be easily kicked off. Key-in-knob locks are very easily broken and then easily released. If a five- or six-pin mortice dead-bolt lock with appropriate cover is used with a lever-action latch, the door will be difficult for burglars to open but easy for the occupants. A key should not be required to open the lock from the inside because this is too dangerous in case of fire. If a lock is being added to a door that has already been installed, one with a vertical bolt may be the most cost-effective.

Breaking glass in or near doors is a potential way to bypass the lock but it is more common to force it. Canadian experience indicates very few cases of doors being opened by burglars who reached through broken windows.

A wide-angle door viewer should be installed to allow occupants to see callers. Very inexpensive viewers are available which give a viewing angle of 160 to 180 degrees. If these are installed at a height of about 1450 mm they should be adequate for most females and a good percentage of males; tall persons will have to stoop. Chain-type door interviewers are to be discouraged because it is almost impossible to provide adequate security unless heavy duty fixtures are used.

Doors and Door Frames

The 25-mm (1 -in.) dead-bolt lock requires that the door frame be almost 50 mm thick. This frame would also be more difficult to pry apart and less

susceptible to warping. If the door frame is not thick enough, more expensive locks are available that clamp the strike plate to the lock. Thl door should be of solid construction and in high risk areas may need special treatment with metal or sirnil: sheathing. It is necessary to ensure that the door adequately supports t h ~ lock. Standards have recently been developed in the U.S.A. for specifyin, door constr~ction.~

Doors that open outward can be held in place even after the pins are removed by providing "jimmy" pins which connect the leaves of the hinges. Alternatively, the pins can be held in place by bolts or screws. On doors with emergency (panic) hardware, an astragal should be specified to stop the hardware from being released by wires worked through the frame separation. If such doors are not to be used for entry they should not have hardware on the outside.

Windows

Standards have been developed in the U.S.A. to reduce the frequency of using windows as a point of entry in all types of buildings4 They are also frequently broken by vandals. Windows can be lifted out of their mountings either by prying o i unscrewing. They can be secured by better frames, non-retractable screws or by pins through the frame and mullion as shown in Figure 2. These pins should be designed to be easily removed for windows that might be used as emergency exits. Casement windows are the most difficult to force open, sash and pivot hung windows are less difficult and sliding windows generally provide little security. Sliding

patio doors can be secured by placing screws in the top track to stop the window or door from being raised. Placing a rectangular wood dowel in the lower track will stop forcible sliding; round sections can be often rolled out of place.

Basement windows are a frequent point of entry, especially the wide low windows common in Eastern Canada. A patented device is currently available

which simply consists of a bar placed horizontally in the window and held in place by pins. If the burglar opens the window he must then saw through the bar.

The use of plastic glazing will be adequate to stop vandalism to inaccessible windows, but in high risk buildings such as

school^,^

such material is easily marred if accessible. Either windows are protected by meshings in such locations or not installed at all. Expanded metal of similar size to ornamental leaden windows can be used to make illegal '

entry difficult. In general, bars or meshings should be positioned on the inside of windows.

Entrances

Entrance design for apartments, hotels and other buildings requires special consideration. However, a few basic guidelines can be stated. Stairs and, if possible, elevators should not allow passage directly from the upper floors to the basement. In high risk areas, occupants should have to transfer at the main lobby to reach the basement. The number of entrances and exits should be limited. In apartments equipped with door controls, telephone communication should be possible between the entrance lobby and the apartments. This communication should be vandal-resistant yet function as an ordinary telephone. There should not be more than one door operated by remote control per building unless special precautions are taken.

Miscellaneous Security Measures A U.S. report found exterior lighting useful in reducing burglary in

residential buildings6 Building managers have for years relied on exterior lighting to improve security. Several police departments

recommend two lights at the front and at least one at the back of homes. The two front lights are to reduce the risk of assault to returning occupants if one light burns out.

Fencing is often relied upon for security. However, most wooden fencing is easily damaged and chain

(

Flgun 2. Locking pin.

fencing creates a hostile environment. Few fences are man-proof. Fencing should only be considered as a demarcation of boundaries and as a screen for privacy. The old fashioned picket fence demarcates the property yet allows surveillance; low hedges do the same. The 2-m verticallv slatted wooden fence creates some privacy but eliminates the possibility for surveillance without being a complete physical barrier. A wrought iron fence can be both decorative and a deterrent to entry.

The use of elaborate features such as security guards, burglar alarms and barred windows are seldom cost effective. In most residential situations they are more of a nuisance than a necessity. Although the participants in the discussions based their

conclusions on experience, the U.S. study Patterns of Burglary resulted in a similar concl~sion.~~everal of the participants had experience with the complex closed circuit television systems and high frequency electronic and infrared detection systems. They felt the usefulness of these systems to be vastly overrated. Frequently the response rate is too slow, the ability for discrimination too limited, and the prolonged concentration too demanding for the operators of the system. The discussions concluded that such systems be reserved for special iristallations.

Conclusion

The most cost effective measures are the provision of robust doors and window locks that are difficult to cheat, and adequate exterior lighting. Concern must be oriented to reducing the impulses that result in crime; for the present, however, these simplistic solutions should be universally applied.

References ' ;.

1 Newman, O., "Design Guidelines for Creating Defensible Space," National lnstitute of Law Enforcement and Criminal Justice, Law Enforcement Assistance Administration, U.S. Department of Justice. April 1976.

2 Building Security, Public Works Canada,

August 1975, (Briefing Document D-9). 3 NILECJ Standard for the Physical Security of Door Assemblies and Components, National lnstitute of Law Enforcement and Criminal Justice, Law Enforcement Assistance Administration, U.S. Department of Justice, May 1976.

4 Physical Security of Window Units, National

Institute of Law Enforcement and Criminal Justice, Law Enforcement Assistance Administration. U.S. Department of Justice, September 1976. (preliminary draft NILECJ-STD-0316.00).

5 Ziesel, J., "Stopping School Prope

Damage," W. E. Henry, ed., availableyom

American Association of School Administrators, 1801 North Moore Street, Arlington, Virginia, 1976.

6 Scarr, H.A., "Patterns of Burglary," 2nd ed., Washington, United States Government Printing Office, 1973.

Byron Johnson, B.Sc. in Mathematics (University of Victoria), B.Sc., in Architecture (University of Edinburgh), joined the Division of Buildin Research, National Research Council of Eanada, in 1975. His main interests at DBR have been concerned with the requirements of building occuoants. In oarticular, the movement of oeoole within buildings and the design of buildings foi

easy use by the hand~capped. A recent outgrowth

of these investi~ations has been the study of

crime prevention through building design: This article is a contribution from the Division of Building Research of the National Research

Council of Canada and IS oublished wlth the

SOMMAIRE

La Division des recherches sur le bitiment du Conseil national des recher- c h e ~ a parraint kcemment des dminaires sur I'importance de la concep- tion des bitiments du point de vue de la prtvention des effractions. Les participants, des sp6cialistes en stcuritt, en conception et en exploitation de bltiments et en sociologie, ont conclu que de simples modifications _B la conception des bitiments et I'utilisation de pieces de quincaillerie de qua- litk sugrieure et & mtthodes de construction amtliorts rtduiraient les ef- fractions de beaucoup. L'article prtsente les questions soulev6es et les con- clusions tirtes lors de ces discussions.

This publication is being distributed by the Division of Building Research of the National Research Council of Canada. It should not be reproduced in whole or in part without permission of the original publisher. The Division would be glad to be of assistance in obtaining such permission.

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ceptable. Ir$

A list of all publications of the Division is available and may be obtained from the Publications Section, Division of Building Research, National Research Council of Canada, Ottawa. K 1 A OR6.