Cpm in construction a manual for general contractors

October 13, History. An edition of The use of CPM in construction This edition was published in by The Contractors in Washington. Written in English — pages. Subjects Construction industry , Critical path analysis , Management. The use of CPM in construction: a manual for general contractors and the construction industry , The Contractors. Classifications Dewey Decimal Class A85 The Physical Object Pagination p. Community Reviews 0 Feedback? Lists containing this Book. Loading Related Books.

October 13, August 4, Edited by IdentifierBot. December 14, These critical tasks cannot be delayed without changing the overall schedule. The process identifies the minimum completion time for the project, based on the tasks, their durations, and their interdependencies. Start by identifying all the tasks in the project, being as detailed as possible. Using a work breakdown structure WBS , which is a hierarchical representation of all the deliverables in a project , can help break down the tasks into manageable pieces.

Each of these steps would be a separate activity in a CPM schedule. Then arrange the tasks by the order they need to be completed. When identifying predecessors and successors for each task, ask:. In our roof example, the tasks were listed above in the order they need to be completed. When determining the order of the tasks, start to look for dependencies — what has to happen before a certain task can start.

These dependencies create the connections between tasks and provide the workflow logic for determining the critical path. When installing a roof, the underlayment has to be completely installed before insulation can be installed in an area. If the roof is large enough, the work can be phased so that insulation can be installed in an area once the underlayment is complete there. This phasing of work is one way to reduce the overall scheduled time.

Next, determine the minimum amount of time it will take for each task to be completed. These durations will be estimates based on the amount of work and the availability of resources like materials and labor. Past projects are the best resource for determining how long a particular task will take. This is done by determining the earliest and latest dates each task can start and be finished, based on the duration of each task and the dependencies identified.

A forward pass through the schedule is conducted to determine the early start and early finish dates for each task. These dates are the earliest a task can start and finish , based on completion of the tasks previous to it. For example, if the installation of underlayment takes five days, the earliest that insulation the next task can start is day five.

If insulation takes three days, the earliest it can finish is day eight early start on day five, plus three days. If there are other tasks that need to be completed before the insulation can be installed, then the earliest it can start will depend on the completion of those other tasks. Once all the early start and finish dates have been determined for each task, then a backward pass is performed to calculate the late start and late finish dates for each task. These are calculated in the same way as the forward pass, except durations are subtracted instead of added.

For example, if the roof cap takes one day to install and the completion date is day 10, then the latest it can start is day nine. If the shingles take three days to install, the latest they can start is day six, and the latest they can finish is day nine subtract three days from day nine, the latest the shingles can finish.

Slack, or float, is determined by taking the difference between the early and late start or finish dates. Download free construction schedule templates for everything from managing projects to tracking payments and submittals.

Almost every construction project has schedule delays of some type. Materials are delayed or workers get pulled off the project to work on another one. Both of these incidents affect the duration of tasks on the schedule. If the task is on the critical path or is more than the slack for that task, the overall completion date for the project can be affected. Related reading: Who pays for a construction delay? There are a couple of ways to deal with delays to tasks on the critical path: crashing and fast-tracking.

Crashing means adding resources to decrease the duration of a task. Fast-tracking involves performing critical path tasks simultaneously to shorten their durations. Fast-tracking is often done when work is phased to allow critical path tasks to be performed in different areas simultaneously. Some of the most popular software platforms for construction scheduling include Procore, BuilderTrend, and CoConstruct.

Software reduces the chance of math errors when calculating durations and start and finish times. It also helps PMs identify the critical path quickly, saving time, particularly on large projects. The software also quickly updates the schedule and the critical path when there is an update to the schedule.

Analysis of delays and the effect of crashing or fast-tracking can be seen almost instantaneously. It also helps quantify the amount of float for each task, allowing PMs to know what tasks can slip without affecting the overall completion time.

One thing that software cannot address is inaccurate information.