Civil Engineering Reference
In-Depth Information
some concealed or enclosed
mechanisms delay burglars
sufficiently to make them give up.
Some hinge mechanisms have special
security features that make it more
difficult to lever open.
The type of glass and method of
glazing can influence how easy it is to
break in. Annealed glass is readily
broken but can leave jagged edges
that will put off an intruder.
Toughened glass is much more
difficult to break, except with a hard
pointed tool, and it can withstand
large deflections without breaking if
a thief tries to lever a window open.
Laminated glass is more expensive
but it contains a clear middle layer
that helps to prevent broken glass
from falling out of the frame. This
will delay a thief from gaining a
quick entry and may cause them to
give up. Sealed double glazing
provides greater security because it is
more difficult and takes longer to
break than single glazing.
How the glazing is fitted into the
frame is important. Some methods fix
the glazing with clip-in beads on the
outside of the window. In some
designs these beads can be easily
sprung off with a sharp tool and the
glazing removed in one piece.
Other external bead systems have
special interlocking parts that prevent
easy removal and therefore are more
secure.
The British Standards Institution
have developed a method for
assessing security of windows, and
windows that pass this assessment
and the BS tests for weathertightness
are awarded a Kitemark.
Insurance companies sometimes
specify the fitting of security devices,
for example bars, which can have
rather unfortunate results, or they
may take a completely commercial
attitude, and simply raise premiums
when the risk of breaking and
entering is perceived to be greater.
Figure 1.62
Measuring the effectiveness of metallised glass in the window and copper mesh in the walls
appropriate methods for fixing
components (eg screws should be of
appropriate size)
●
tamper-proof fixings if they are
accessible from the outside
●
appropriate concealed cabling or
conduits and any external cables
protected if an intruder alarm
system or supplementary external
lighting is to be installed
Methods of testing and assessment
for specific components, particularly
glazing and locks, are covered by
British and overseas standards. British
Standards are also available for bullet-
resistant, bandit-resistant and safety
glazing
(70,71,72)
.
Methods of assessment for other
components for use in low risk areas
are being developed by BRE and the
Loss Prevention Council. Some
European national standards exist and
there is a possibility therefore of a
European standard eventually.
●
open trickle vents in windows
presenting a high security risk
●
security provisions restricting
means of escape during a fire
●
installation of appropriate
electronic and electrical devices (eg
intruder alarms)
●
Electromagnetic screening
Electromagnetic screening can be
applied to walls, windows and doors in
commercial and industrial buildings.
It uses techniques that are unobtrusive
and do not impair the quality of the
working environment, while
providing an acceptable level of
performance at reasonable cost
(Figure 1.62). In addition to the
effectiveness of the shielding of
different materials, such matters as the
quality of joints around doors and
windows are important
(73)
.
Standards
Overall performance requirements for
the security of walls and their
component parts are not generally
available. Prescriptive requirements
are contained in BS 8220 and
organisations concerned with high
security buildings such as banks or the
MOD have their own in-house
standards. Because of the nature of the
subject these requirements are not
generally available.
Security provision
The following factors should be
considered:
●
doors, windows, locks and other
associated hardware that are of
appropriate strength and
performance
