Construction length forecasting in a project can be accomplished in a variety of ways, depending on the stage of construction planning. Construction duration forecasting instructs the project owner to give the contractor enough time to perform the work. The contractor, on the other hand, could create a realistic and practical comprehensive schedule at a low cost and within a short time frame.
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The duration of construction can be defined as one or more of the following:
1) The duration of construction due to a critical path in which the duration of individual items of work or activities in a sequence cannot be lowered any further (Barrie and Paulson, 1992).
2) Duration refers to the amount of time it takes to perform a task or activity. Furthermore, the construction period is dictated by the owner’s demand to inhabit, operate, or rent the project’s completed space (Callahan et al., 1992).
3) Construction duration is a time estimate based on a cost analysis of one or more methods of carrying out the work; it is usually estimated in the first instance for normal conditions (Pilcher, 1992).
4) Construction duration refers to the amount of time it takes to execute and complete a task using all project information and resources while staying within a budgeted budget (Kwaku, 1994).
5) Construction time is defined as the time it takes from the start of site work to the handover of the building to the client. It is normally specified prior to the start of the construction process (Nkado, 1995).
Construction length is defined in this study as the time allotted by the owner for the contractor to finish the project under normal working conditions, standard construction practises, and at the lowest possible cost. It begins when the contractor is given the go-ahead and ends when the construction work on the job site is completed. It also covers delays induced by unforeseen events, such as changes in the scope of work (changing conditions and change orders), additional work, material supply, location, weather, and site work conditions. Significant adjustments that occur after the scope of work has been completed are not included.
Scheduling and Schedulers
Controlling construction time necessitates a well-thought-out strategy and dedication from all parties involved (McNulty, 1982). The term “schedule” refers to a methodical plan. The scheduling process, which follows logically from the planning process, determines the time of activities (Callahan et al., 1992). It’s usually used to keep track of how long a project takes (Callahan et al., 1992). Scheduling is critical to the financial proposal and budgeting of both the owner and the contractor (Peurifoy and Ledbetter, 1985; Kaka and Price, 1991).
The scheduler and/or planner create the schedule. Estimator, manager, superintendent, subcontractor, architect, engineer, owner, and materials’ suppliers are some of the persons the scheduler or planner may meet or communicate with when developing a timetable (Callahan et al., 1992). They may need to look over the contract, drawings, and specifications, as well as do some reconnaissance on the site. They also require information on manpower and productivity. (Pilcher, 1992; Cahallan et al., 1992). Aside from the schedule, systematic monitoring is required to provide early warning of constraints as well as creative solutions to overcome them (McNulty, 1982).
Computers can now help the scheduler or planner by storing and categorising data and conducting mathematical calculations, but they cannot provide intellectual direction (Callahan et al., 1992). Human talent and expertise are still required, so the scheduler or planner can estimate the construction duration based on previous experience with similar projects (Pilcher, 1992). The scheduler or planner may make decisions based on a variety of factors, including location and access, weather, space and site work conditions, project complexity, quality of workmanship, material delivery, and economic or marketing considerations (Pilcher, 1992).
Forecasting Construction Duration
1. Required inputs:
The following are the basic inputs for project scheduling:
1) make a contract;
3) a description
4) assets (materials, manpower, and output); and
5) Other restrictions, such as weather and site circumstances (Burgess and White, 1979; Fisk, 1982; McNulty, 1982; Peurifoy and Ledbetter, 1985; Ashworth, 1988; Barrie and Paulson, 1992; Callahan et al., 1992; Pilcher, 1992).The contract may include a specific completion date. As a result, the scheduler or planner may use this time period in conjunction with other factor limitations to construct the schedule. To begin, it is common practise to plan the timetable for normal circumstances by assuming one or more methods of completing the task at the lowest possible cost (Nkado, 1992; Pilcher, 1992). When a task or activity must be completed in a shorter amount of time.
The following physical characteristics of the project are depicted in the drawings: 1) function; 2) height; 3) systems (e.g. plumbing, firefighting, and lighting); and 4) complexity (Ireland, 1985; Ashworth, 1988; Pilcher, 1992; Nkado, 1992). In other words, dimensions and descriptions are used to show information on the pictures (Ashworth, 1988). The plans also reveal the project’s materials and installed equipment, as well as the plant and construction equipment (Ashworth, 1988; Peurifoy and Ledbetter, 1992). Meanwhile, the contract may include work limits such as construction cost, time, payment, inspection, work technique or circumstances, delays, and damages. In addition, the specification may cover material quality, workmanship, and working methods (Barrie and Paulson, 1992).
2. Resource scheduling
The scheduler or planner must assign resources, such as supplies and labour (or a working team), to each activity or job at the appropriate time. As a result, the resource schedule is concerned with the levelling and distribution of all required resources (Peurifoy and Ledbetter, 1985). Within the project’s duration, the former smoothes out the peaks and valleys in resource use. The latter finds the shortest project duration possible given the resources available.
3. Other judgements
They must also schedule preliminary work, such as the construction of a facility, as well as mobilisation (Peurifoy and Ledbetter, 1985). After the construction is finished, there is usually time for remedial work and site cleanup.
The scheduler or planner can change the timetable to accommodate numerous constraints, such as location and access, weather, space and site work conditions, project complexity, quality of workmanship, material delivery, and economic or marketing factors (Barrie and Paulson, 1992; Pilcher, 1992).
Some Methods for Project Scheduling
Gantt or bar chart, Critical Path Method (CPM), and Program Evaluation and Review Technique are just a few examples of schedules (PERT). Each has its own set of benefits, drawbacks, and application areas in which it excels. They’re a way of visualising a construction programme (Pilcher, 1992), and they’re utilised for project planning, management, and control (Burgess and White, 1979; Fisk, 1982; McNulty, 1982; Barrie and Pualson, 1992).
A bar depicts the activity and its duration on a Gantt chart. It’s also known as a bar chart. A Gantt chart or bar chart can show a lot of expected and actual data for: 1) cashflow; 2) manpower and/or manpower by trade; and 3) productivity (Barrie and Paulson, 1992; Callahan et al., 1992).
A construction project is separated into various activities in CPM scheduling. A single labour step with an identifiable beginning, middle, and end is referred to as an activity (Callahan et al., 1992). To put it another way, the activity is time-consuming. CPM is based on a network diagram, which requires nodes and arrows. It is divided into four sections: 1) identifying activities; 2) logical sequencing; 3) network construction; and 4) resource allocation (Barrie and Paulson, 1992). The creation of the CPM schedule was separated into six phases by Callahan et al. (1992):
1) grasping the scope of the project;
2) the definition of a conceptual approach
3) the schedule’s physical creation;
4) the use of computers
Project Delays and their Causes:
The duration of a project is usually determined by the owner. Many buildings are seasonal in nature, so their completion and operation are limited. For example, a school must open in September, a retail outlet must open for booking in August to meet the Christmas sale season, and an apartment must open in May to meet the spring market (McNulty, 1982). Construction time has an impact on the owner’s financial interests, such as selling price and on-site management. The contractor is then in charge of detailed planning and scheduling to ensure that the project is completed within the owner’s deadline. The actual construction time, on the other hand, is divided into two parts:
1) the duration of the contract;
2) There is a delay.
Delay is the period of time during which some aspects of a building project have been delayed or not completed due to unforeseen events (Barrie and Paulson, 1992). If necessary, the contractor may need to set aside more funds for corrective efforts in order to stay on time; otherwise, the contractor may face liquidated damages costs for failing to meet the owner’s expectations (Fisk, 1982; McNulty, 1982).
A change in the working drawing is one of the most important factors impacting the construction time, as it may create a delay beyond the contract time (Sadashiv, 1979; Chan and Kumaraswamy 1995). The causes of delay, according to Barrie and Paulson (1992), can be divided into four categories.