Building maintenance
strategy: a new management
approach
R.M.W. Horner, M.A. El-Haram and A.K. Munns
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Construction Management Research Unit, Department of Civil
Engineering, University of Dundee, Dundee, Scotland
Introduction
Building maintenance is a major activity in most countries. It is estimated that
in the United Kingdom it currently accounts for expenditure of some £20 billion
(Technology Foresight Construction Sector Panel, 1995). Accordingly, any
reduction in resources applied to building maintenance will have a visible effect
on the national economy. For this reason, a current research project supported
by EPSRC at the University of Dundee is paying particular attention to the
development of a new maintenance management approach aimed at reducing
the maintenance costs of existing building stock.
The easiest way to cut maintenance costs is to stop doing maintenance. This
approach is simple, but the long-term results are usually very costly. Thus, the
goal of the new approach is to carry out as little maintenance as possible as
infrequently as possible while at the same time preserving the availability of the
services facilities, the building elements and the whole building. In other words,
maintenance should be carried out only when necessary to ensure the
continued, safe and profitable use of the building at acceptable levels of
satisfaction or when there is the possibility of extending the useful life of the
elements of the building. Finding an appropriate maintenance strategy is the
most difficult task facing maintenance management in determining an optimal
approach to reducing the financial expenditure and total life cycle costs. This
paper describes a new, systematic framework for selecting a suitable
maintenance strategy for each individual item in a building.
Building maintenance
Building maintenance is defined as “work undertaken in order to keep, restore
or improve every part of a building, its services and surrounds, to a currently
accepted standard, and to sustain the utility and value of the building” (Seeley,
1976). The objectives of building maintenance are therefore (Alner and Fellows,
1990):
The financial support of the Engineering and Physical Sciences Research Council is gratefully
acknowledged.
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Engineering, Vol. 3 No. 4, 1997,
pp. 273-280. © MCB University
Press, 1355-2511
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•
to ensure that the buildings and their associated services are in a safe
condition;
•
to ensure that the buildings are fit for use;
•
to ensure that the condition of the building meets all statutory
requirements;
•
to carry out the maintenance work necessary to maintain the value of the
physical assets of the building stock; and
•
to carry out the work necessary to maintain the quality of the building.
In maintaining a building, there are usually several strategic options available
to management, and many alternative decisions to be considered. There is, for
example, the possibility of reducing the demand for maintenance by addressing
the actual cause of failure and identifying its consequences. For instance, it may
be necessary to decide whether to repair or replace an item, and whether to
carry out periodic maintenance at fixed intervals or simply to respond to the
requests of the users. Thus, building maintenance can be divided into three
strategies:
•
corrective;
•
preventive;
•
condition-based.
Corrective maintenance
Corrective maintenance is the simplest type of maintenance strategy, where an
element in a building is used until it breaks down. It covers all activities,
including replacement or repair of an element that has failed to a point at which
it cannot perform its required function. Corrective maintenance is sometimes
referred to as failure-based or unplanned maintenance. Corrective maintenance
tasks often take places in an ad hoc manner in response to breakdowns or user
requests (David and Arthur, 1989). Thus, corrective maintenance can be
extremely expensive for two reasons:
(1) The failure of an item can cause a large amount of consequential damage
to other elements in the building. For example, failure of the roof could
cause damage to the ceiling and the interior of the building.
(2) Failure of an item can occur at a time which is inconvenient to both the
user and the maintaining authority. This can make manpower and spare
parts planning extremely difficult.
However, corrective maintenance is still an important part of any maintenance
management strategy, as we shall see later in this paper. It is from such work
that we can gather vital predictive information.
Preventive maintenance
Preventive maintenance was introduced to overcome the disadvantages of
corrective maintenance, by reducing the probability of occurrence of failure and
avoiding sudden failure. This strategy is referred to as time-based maintenance,
planned maintenance or cyclic maintenance. Preventive maintenance tasks are
performed in accordance with a predetermined plan at regular, fixed intervals,
which may be based for example on operating time. Such a strategy is
frequently applied to external or internal paint work. The following are the
advantages of preventive over corrective maintenance (Raymond and Joan,
1991):
• maintenance can be planned ahead and performed when it is convenient
to the building’s user;
• maintenance costs can be reduced by avoiding the cost of consequential
damage;
• downtime, the time that an element of the building or the whole building
is out of service, can be minimized so the habitability of the building can
be increased; and
• the health and safety of the user can be improved.
Nevertheless, preventive maintenance has some disadvantages which must be
minimized (El-Haram, 1995):
• Planned maintenance is performed irrespective of the condition of the
building elements. Consequently, a large number of unnecessary tasks,
will be carried out on elements that could have remained in a safe and
acceptable operating condition for a much longer time.
• The condition of an element may end up worse than it was before, as a
result of human error during the execution of the maintenance task.
• Planned maintenance tasks are usually very demanding in terms of
spare parts and labour.
Condition-based maintenance
Condition-based maintenance is defined as: “Maintenance carried out in
response to a significant deterioration in a unit as indicated by a change in
monitored parameter of the unit condition or performance” (Kelly and Harris,
1978). The condition-based maintenance concept recognizes that a change in
condition and/or performance of an item is the principal reason for carrying out
maintenance. Thus, the optimal time to perform maintenance is determined
from a condition survey used to determine the actual state of each constituent
item in a building. In this strategy, maintenance tasks are determined and
planned by efficiently monitoring the building’s elements such as walls, floors,
roof and service equipment such as boilers, pumps, and heating system, to
identify which element or piece of equipment requires maintenance before a
major failure occurs. To gain the full advantage of applying condition-based
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maintenance, the condition of an item must be monitored to identify whether
there is any evidence of change from a normal to an abnormal condition. This
can be done by selecting the parameter which best describes the condition of the
item and monitoring changes using suitable condition monitoring tools.
Condition assessments can vary from simple visual inspections to more
advanced inspections using a variety of condition monitoring tools and
techniques.
A new approach to maintenance management
Current building maintenance strategies, whether based on planned or
unplanned maintenance, are most likely to be budget driven. This means that
maintenance is not carried out according to actual need, but is dictated by
financial priorities decided at the time or during the previous 12 months.
Although theoretically the budget should be built up as a result of estimated
needs, it is almost invariably based on previous years’ figures, modified for
changes in the number of buildings, specially agreed programmes of planned
maintenance and inflation forecasts (Spedding, 1987). Three methods are
currently used for constructing a budget for estate-based management
organizations; none is entirely satisfactory and each produces a different
budget (Lee, 1987):
(1) Base this year’s budget on last year’s expenditure with an allowance for
inflation.
(2) Use the Department of Environment (DoE) or other formula for
calculating the maintenance element of the estate budget.
(3) Use a stock condition survey to quantify the size of the maintenance
task.
In contrast to the way that current building maintenance strategies are selected,
the new maintenance management approach is based on the failure
consequences of each item in a building. Thus, the objective of maintenance
management is to prevent, to minimize and to repair building defects by
enhanced planning and implementation using appropriate materials and tools
at the right time and minimum total life-cycle cost.
The maintenance management decision diagram
The maintenance management decision diagram is a logical process used to
select an appropriate and cost-effective maintenance strategy for each item or
group of items in a building. Its objective is to determine the best combination
of maintenance strategies for a building by selecting the optimum maintenance
strategy for each individual item in the building, taking into consideration
health, safety and satisfaction of the user and the costs of maintenance tasks.
The first step in developing the maintenance management decision diagram
is to carry out a comprehensive review of all constituent items in a building.
This can be done by breaking the building down into the physical elements and
items of each functional system and subsystem. Engineering failure analysis
provides insight into the type of failures that an item in a building is likely to
experience. So each item within the building should be analysed from the point
of view of failure. It is especially important to identify the consequences of
failure. The engineering tool which is used to perform this task is a failure
mode, effect and consequences analysis (FMECoA) (El-Haram et al., 1996). As a
result of this analysis, all the constituent items in the building can be divided
into two groups depending on the significance of the consequences of failure
(El-Haram and Knezevic, 1995).
Significant items
Significant items are those whose failure affects health, safety, environment or
utility (including cost).
Health, safety and environmentally significant items. To determine health,
safety and environmentally significant items (HSESIs), it is necessary to find
out exactly how the item might affect the environment and the health and safety
of the user when it fails. Niczyporuk (1994) defines a safe object as one which
causes no hazard in relation to life, health or the environment. It is also defined
as freedom from unacceptable risk or personal harm. Risk is the combined
effect of the chances of occurrence of some undesirable failure and its
consequences in a given system. Thus, HSESIs are those whose failure creates
a possibility that the user could be injured or killed, or that environmental
standards could be breached.
Util ity significant item. An item is utility significant if the cost of
maintenance is less than the cost of failure. In determining the cost of failure, it
is necessary to take account of any loss of availability which may result from
the failure. Thus, all items whose failure is likely to have an effect on the
revenue, direct and indirect maintenance costs, quality, user satisfaction,
appearance, serviceability or availability of the building are potentially utility
significant.
Care should be taken to ensure that all items that have failure consequences
are included in the list of significant items.
Non-significant iems
Non-significant items are those items whose failure has no significant effect.
This means that the failure affects neither health, safety, environment nor
utility.
Selection of building maintenance strategy
Once significant and non-significant items are identified, the next step is to
select an appropriate maintenance strategy for each item in the building.
Generally speaking, all three types of maintenance strategies could be applied
to every item in the building, but only one will yield optimal results. The process
is illustrated in Figure 1.
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Figure 1.
Building maintenance
decision diagram
Condition-based
maintenance
(CBM)
Y
Is the cost of
applying CBM less
than the cost of
applying FBM?
Y
N
Failure-based
maintenance
(FBM)
N
Is the cost of
applying TBM less
than the cost of
applying FBM?
N
Time-based
maintenance
(TBM)
Y
Is the on-line
condition monitoring
technique available
and costeffective?
Failure-based
maintenance
(FBM)
Y
Can the
condition of the
HSESI be
monitored?
Y
Can the
condition of the USI
be monitored?
N
HSES items
Significant items (SI)
List of a building’s
constituent items
278
US items
Key
HSES = Health, safety and environment significant
US = Utility significant
Time-based
maintenance
(TBM)
N
Condition-based
maintenance
(CBM)
Non-significant
items (NSI)
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Corrective maintenance
Corrective maintenance is most likely to be the appropriate maintenance
strategy for:
• non-significant items; and
• utility significant items whose condition cannot be monitored and for
which the cost of applying time-based preventive maintenance is less
than the cost of applying corrective maintenance.
Preventive maintenance
Time-based preventive maintenance is most likely to be the appropriate
maintenance strategy for:
• health, safety and environmentally significant items whose condition
cannot be monitored;
• health, safety and environmentally significant items whose condition
can be monitored, but for which the online condition monitoring
techniques either are not available or are not cost effective; and
• utility significant items whose condition cannot be monitored and for
which the cost of applying time-based preventive maintenance is less
than the cost of applying corrective maintenance.
Condition-based maintenance
Condition-based maintenance is most likely to be the appropriate maintenance
strategy for:
• health, safety and environmentally significant items whose condition
can be monitored and for which on-line condition monitoring techniques
are available and cost-effective;
• utility significant items whose condition can be monitored and for which
condition-based monitoring techniques are available and cost-effective;
and
• utility significant items whose condition can be monitored and for which
the cost of applying condition-based maintenance is less than the cost of
applying corrective maintenance.
Conclusions
To determine an optimal maintenance strategy for a building, it is necessary to
integrate the three types of maintenance strategy because:
• not all items are significant;
• not all significant items can be condition monitored;
• condition monitoring techniques are not always available; and
• the application of condition monitoring techniques is not always costeffective.
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This approach will allow maintenance engineers and managers to make
decisions in advance about:
• selecting the most cost-effective maintenance strategy for each
individual item in the building; and
• the optimal allocation of logistics resources such as spare parts, tools,
and personnel which are needed for the execution of maintenance
activities.
Introducing this approach to building maintenance management is expected
both to reduce building maintenance costs and to improve the health, safety and
satisfaction of the user. Although the paper has proposed a new approach to
building maintenance management, testing of its effectiveness at this stage is
hampered by the lack of reliable failure data and maintenance cost data.
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