Chap 4 Sch&Plmin

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Chapter - IV Scheduling and Planning


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Introduction

The Construction time management is the backbone of construction industry as it governs

directly or indirectly the elements involved in the project. As discussed in the earlier chapter, the construction

cost, quality and other related elements gets affected with the delay in construction project. This shows the

vulnerability of construction project due to improper construction time management.

Construction Time management is basically scheduling and planning the constructionprocesses, activities in a logical sequence in accordance to the available resources and project objectives. The

terms Planning and Scheduling do appear as synonyms in general, but they are different in the context of

construction time management. These terms and the scheduling methods will be dealt in this and the further

chapters.

Scheduling and Project Planning

Scheduling and planning are two terms that are often thought to be synonymous. But theyare not. Scheduling is actually a part of planning in construction Project. The term Planning is used in different

fields under different contexts. In case of construction industry and construction projects Planning a project

means

" the process of choosing the one method and order of work to be adopted for a

construction project from all the various ways and sequences in which it could be done "

The PMI (Project management institute) defines the project Planning process in the

PMBOK as " those processes performed to establish the total scope of the effort, define and refine the

objectives, and develop the course of action required to attain Project objectives ". Project planning serves as afoundation for several related functions, such as cost estimating, scheduling, project control, safety management

and others that enhances the construction project.

There are various key terms and various elements that are to be understood before

understanding project scheduling and planning. The descriptions of a few key terms and elements of a schedule

are given below in order.

Deadline : a specific point in time, such as the day on which part of a project must be completed. For example,

the deadline of excavation activity of the construction project means that the excavation part should

be completed at any cost by the end of the specified day in the schedule.

Period : it is the time span taken for ant certain activity or process for its completion. For example, the time

period of 14 days for centering means that the centering activity takes 14 days to be completed.

Tasks : these are the very foundation of the schedule and refer to self - contained work units. For example,

tiling the ground floor is a task. And when several tasks are combined then the result is a Summary

task. Example, tiling and plastering)


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Task Duration & Duration planning : it is the time needed to complete a task. The calculation of duration is

referred to as Duration Planning.

Sequence Planning : the construction project consists of various activities which are formed under the WBS of

Project. These activities are to be linked logically in certain order so as to create a proper

and efficient schedule for the project. This process of establishing the dependencies

between activities is referred to as Sequence Planning.

Fig.4.2 : Duration Planning and Sequence Planning

Construction Scheduling

The duration of the activities and the sequence planning of them when taken together

form the basis of Construction Scheduling. Scheduling is the determination of the Timing and sequence of

operations in a project and their assembly to give the overall completion time of the project. As mentioned

earlier Scheduling focuses on one part of Planning effort.

The difference between project planning and scheduling can be understood from the

figure below. Project planning actually deals with the overall activities relating to the project. The selection of

contractors, where, when, how, by whom, at what cost etc. these all will be answered by the project planning

process. The Scheduling part deals with the "when" part in detailed level.

Fig. 4.3 : Construction project Scheduling


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Fig. 4.4 : The relation between Construction Project Planning and Scheduling

Milestone

A milestone is a task without any duration. It is a special event entered separately into the

schedule. Typical scheduling milestones include the start of construction, completion of the building structure,

sealing the building envelope, final inspection and putting the building into operation.

Sequential dependencies

In most cases, tasks are not isolated items on the schedule but are integrated into a web of

dependencies with other tasks. There can be several reasons for this. The normal case is a Sequential

dependency. Task B can begin only when task A is finished i.e. for e.g. ground floor walls ground floor

ceiling upper floor walls.

Some tasks can only be performed jointly in a parallel process e.g. setting up scaffolding

floor by floor as the structure of a multistory building goes up. Often these process dependencies can be broken

into sequential dependencies by using a higher level of detail. It is often impossible for contractors to work in

parallel during a number of construction phases where one activity (task) interferes with another. This is why it

is essential for planners to examine mutual dependencies between specialized tasks and, if necessary, to divide

the project into optimal construction phases.

Various types of relationships play an important role in the graphic representation of

dependencies between two tasks. Construction scheduling distinguishes between four types :

Finis-to-start : Task B can only start after task A is finished. This is the most common type of relationship and

may apply to activities such as the construction of interior walls (A) and interior plastering (B).


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Finish-to-finish : Task A an task B must be completed by the same time. This type of relationship exists when

tasks A and B provide the foundation for an additional task. Examples are installing windows (A) and sealing

the roof (B), which create the airtight building envelope necessary for interior work.

Start-to-Finish : Task B must end when task A begins. In this type of relationship, one task can be scheduled at

the least possible point in time before it interferes with another task.

Start -to-start : Task A and task B must start at the same time. This makes sense if the work can be performedin parallel - if, for instance, workers from one trade can use a crane that is operated by another contractor to

deliver large building elements.

Fig. 4.5 : Different types of Relationships between activities.

Forms of Representation

There are different ways to represent a schedule graphically. The following forms of

representation are used to communicate schedule contents in a clear and useful manner, depending on the goal

and purpose of the Schedule.


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Scheduling is the determination of the timing and sequence of operations in the

project and their assembly to give the overall completion time. As mentioned

previously, scheduling focuses on one part of the planning effort.

Project planning answers the questions What is going to be done? How? Where?

By

whom? and When (in general terms, the projects start and end)? Scheduling deals

with

when on a detailed level.

In fact, scholars have generally separated planning from scheduling CPM

separates

planning and scheduling, and once project information is collected and expressed

as a network plan and activity time estimates assigned, CPM calculations can be

made.

Planning ceases and scheduling starts when the first computation is performed that

shows a project duration. The project duration is then compared with the desired

schedule and scheduling begins. (OBrien and Plotnick, 2009, p. 417)

To get an idea about the relationship between project planning and scheduling,


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assume that you are planning a family vacation project for next summer. Your

plan

may include considerations such as these:


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