the complexity in construction projects increased, simply managing the obtained
float values and critical path(s) by the CPM method usually results in more
difficult schedule control and, consequently, in incorrect decision making due
to non-realistic float values.
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This study thoroughly
reviewed various float types in the
project management systems, and discussed five managerial essentials and
three proactive strategies on mitigating challenging float-related problems
based on the perspective of managing schedules by controlling floats.”
comments and suggestions, the outcomes of this study not only improve the knowledge
level on schedule management but also provide a better understanding of float
management to improve the quality of schedule management.
Project float used
by developers and project managers to planning &schedule the specific time
of tasks as well as the time framed for
making decisions to best ensure construction projects come in on time. Total
float is the span of time between the target end date of the last task on the
critical path and the target date for project completion.
float is the time an individual task can be delayed before impacting the task
that follows it, defined as the difference between the task’s earliest and
latest possible finish dates.Float can allow more time for working on a task
when necessary. Otherwise, resources can be repurposed for another task.”
Employees working with
multiple teams can put more time into other tasks that are lagging. Total float
is often represented as a positive or negative number representing the number
v Float Definition:
The definition of float in general is the
amount of time that a task, network path or project can be delayed without changing
the deadlines of other successor tasks or
Completion date of the project and sometimes float called
v How to find Float ?
simplest way to compute float is to subtract the time you’ve allotted to
complete a task from the time the task actually takes. Tasks that have zero
float can be considered as part of the “critical
path”, because any delay on these tasks means a delay to the project
Benefits of the floats:
They are many benefits of the floats in
Planning phases, Float usage on paths of
non-critical tasks have an effect on productivity, recourses and comfort in
In the Planning phases of a project, float
can be used to improve productivity &efficiency but at construction phase
the consumption of floats can effect negatively to these factors and they are
two main benefits of the floats:
§ First one : Delay analysis:
Construction projects continue to suffer
delays. Things go wrong and the project’s completion date gets pushed
back, with someone to be blamed for it.
In practice, attempts are made to identify the causes of delays
and schedules are modified to incorporate revised duration and
new project time. The analysis itself is usually complex
and can be aided by a computerized approach. Different delay analysis
techniques are currently used by practitioners in the construction industry.
Second one: Resource Leveling:
In project management, resource leveling is
defined by the (PMBOK Guide) as “A technique in which start and finish
dates are adjusted based on resource constraints with the target of balancing
demand for resources with the available supply.”
project planning activities, the manager will attempt to schedule certain activitys
simultaneously. When more resources such as machines or people are needed than
are available, or perhaps a specific person is needed in both tasks, the activity
will have to be rescheduled concurrently or even sequentially to manage the
constraint. Project planning resource leveling is the process of resolving
these conflicts. It can also be used to balance the workload of primary
resources over the course of the projects usually at the expense of one of the
traditional triple constraints (scope, cost, time).
leveling is also useful in the world of maintenance management. Many
organizations have maintenance backlogs. These backlogs consist of work orders.
Without resource-leveling the organization (planner, scheduler and supervisor)
is most likely performing subjective selection.
§ Example of resource leveling:
v Different types of
are several different types of floats in construction management like
Float, Free float, Interfering Float, Independent Float and Safety Float.
Total Float (TF):-
float is what many of us are aware of, and is commonly referred to as a float.
Total float is
the amount of time that an activity can be delayed without delaying the project
completion date. On a critical path, the total float is zero.
Total float is called
sometimes “slack”.You can calculate the total float by subtracting the
Early Start date of an activity from its Late Start date (Late Start date –
Early Start date), or Early Finish date from its Late Finish date (Late Finish
date – Early Finish date.
TF = ( LS – ES )or TF = (LF – EF).
OR. TF = (LF – Duration – ES).
Free Float (FF):-
float is the amount of time that an activity can be delayed without delaying
the Early Start of its successor activity.
free float can be calculated by subtracting the Early Finish date of the
activity from the Early Start date of next activity (ES of next Activity – EF
of current Activity
activities are converging to a single activity, only one of these two
activities may have free float.
FFi = min(ESi+1) – Efi
(ESi+1) is the least (i.e., earliest) of the early start dates of succeeding
Interfering Float (Int. F(:-
float is the time span in which the completion of an task may occur and not
delay the termination of the project but within which completion will delay the
start of some other following task.
Int. F = TF ? FF
Independent Float (Ind. F):-
independent float is a very convenient measure of scheduling freedom. The
independent float of task is the maximum time can be delayed without delaying
successor activities, if all prior activities are finished as late as possible.
It gives a measure of time available if the worst possible conditions prevail
in the predecessor activities.
It also gives
an indication of the possible degree of decoupling the activity from the others
in the project, hence the name independent.
In other words
– it’s the free float of the late dates.
Ind. F=min (ES of the Succ.) – max (LF of the
Pred.) – D
Safety Float (SF(:-
Safety Float is the maximum time an activity
can be delayed without affecting the final project completion if predecessor
activities are completed as late as possible. This new measure appears to be
one of the more useful float measures when scheduling a particular activity.
only successor activities to be delayed, not the entire Project
In other words
– it’s the total float of the late dates.
SF=LF – (LF of
the Pred.) – D
Who owns the Floats?
The ‘float’ is the amount of time that
non-critical activities can absorb, in excess of their original intended
duration, without impacting on the critical path of the works as a whole.
may argue that it ‘owns’ the float because, in planning how it proposes to
carry out the works, it has allowed additional or ‘float’ time to give itself
some flexibility in the event that it isn’t able to carry out the works as
quickly as it planned. If there is a delay to the Contractor’s progress for
which the Contractor is not responsible, it may contend that it is entitled to
an EOT, even if the delay to progress will not result in the contract
completion date being missed but merely in an erosion of its float. In
addition, the Contractor may want to accelerate the works to keep the float in
full and claim its costs of doing so.
On the other
hand, an Employer may say that the Contractor has no contractual remedy for
being prevented from completing the works at any time prior to the contract
completion date, and is therefore not entitled to an EOT unless the delay to
progress will result in the contract completion date being missed. So, the
Employer would say that it ‘owns’ the float.
v What does the Contract say?
The issue of who ‘owns’ the float is often the cause of disputes
between parties to a construction contract over entitlement to EOTs. The first
port of call in the event of a dispute arising on this issue will be to review
the terms of the contract. In the united of kingdom, the express issue of
‘float’ rarely appears in standard form contract conditions. However, the
answer may appear in the EOT provisions. Where the EOT clause states that an
EOT is only to be granted if the Employer delays completion beyond the contract
completion date, then the likely effect of that wording is that the total float
has to be used up before an EOT will be due (i.e. the Employer would ‘own’ the
float). If, on the other hand, the EOT clause states that an EOT will be due
whenever the Employer’s delay makes the Contractor’s planned completion date
later than it would have been if it were not for that delay, then the total
float will probably be available for the benefit of the Contractor.
However, most contracts give no indication as
to whether an Employer delay has to affect the contract completion date or
merely the Contractor’s planned completion date before an EOT is due. That is
why parties should ensure that this issue is properly addressed at contract
the Contract is silent, does the Contractor own the float?
to the 1999 case of Ascon Contracting Limited v Alfred McAlpine Construction
Isle of Man ltd., if the contract was silent on the issue of float, the general
approach adopted in the UK was that the Contractor would own the float because
it was the Contractor who had built the float into the program to provide a
cushion for unforeseen problems. However, the current approach as established
in the McAlpine case and supported by the Society of Construction Law Delay and
Disruption Protocol, is that an Employer delay has to be critical before an EOT
will be due. This has the effect that float is not time for the exclusive use
or benefit of either the Employer or the Contractor but, rather, exists for the
benefit of all parties to the contract. So, even if an Employer delay causes a
delay to a Contractor’s planned completion date, an EOT will not be due unless
that delay resulted in a delay to the overall contract completion date.
terms of what that means for acceleration costs, in the event that a Contractor
sought to accelerate the works in order to keep the float, the current position
is that, unless the contract states otherwise, such costs would not be
recoverable as the float would belong to the project rather than to one of the
position can lead to unfairness and ambiguity. For instance, under contracts
where Employer delay has to affect the critical path before the Contractor is
entitled to an EOT; if an Employer delay occurs first and uses up all the
float, then the Contractor can find itself in delay and paying LADs as a result
of a subsequent Contractor delay which would not have been critical if the
Employer Delay had not occurred first. However, on the other hand, under
contracts where the Employer delay only has to affect the Contractor’s planned
completion date, the Contractor is potentially entitled to an EOT every time
the Employer delays any of the Contractor’s planned activities, irrespective of
their criticality to meeting the contract completion date.
position established in the English courts is that neither party owns the float
if the contract is silent on the issue and the Contractor will only be entitled
to an EOT for an Employer delay which impacts on the critical path i.e. the
courts have elected not to confer a benefit on either party in the event of the
parties’ failure to deal with the issue in their contracts.
the position taken by the Courts, it’s important to deal with the issue of
float during the contract negotiation stage.