Some tasks in your project may have certain
relationships with other tasks in your project. For example, you may
have a task that can’t begin until another task has ended. These
relationships are called dependencies. Project offers four different types of dependencies for your project’s tasks:
Finish-to-Start (FS)— A finish-to-start dependency is one in which a second task cannot begin until the first task has ended.
Start-to-Start (SS)— A start-to-start dependency is one in which a second task cannot begin until the first task has begun.
Finish-to-Finish (FF)— A finish-to-finish dependency is one in which a second task cannot finish until the first task has finished.
Start-to-Finish (SF)— A start-to-finish dependency is one in which a second task cannot finish until the first task has begun.
Figure 1 shows these four types of dependencies.
Let’s walk through an example
that uses all four of these types of dependencies. In this example, you
are planning to remodel the kitchen and dining area in a home. You use
Project to track each of the tasks involved in this process.
Here are the tasks you want to track for the remodel:
Rewire kitchen— This involves moving outlets, wiring through cabinets for a built-in microwave, and adding an outlet on a kitchen island.
Install new cabinets— This involves installing new wall cabinets, and cabinets to support a new countertop.
Paint— This involves painting both the kitchen and dining areas.
Install counters— This involves placing a new countertop on top of the new cabinetry.
Install new floors— This involves placing new flooring in both the kitchen and dining areas.
Install new appliances— This involves installing several new kitchen appliances.
Each task has some sort of
dependency on another task. The “Rewire kitchen” task can’t be finished
until the “Install new cabinets” task has started, because some of the
wiring needs to be done through the new cabinetry (wiring for a built-in
microwave, and an outlet on the island). This is a start-to-finish
dependency in Project.
The “Paint” task has a
start-to-start dependency on the “Rewire kitchen” task. That is, the
painting can’t start until the electrician has started the process of
rewiring. The electrician needs to have moved openings for outlets and
light fixtures, as necessary, before the painters can come in and begin
painting the kitchen and dining areas. The electrician doesn’t need to
be done with all of his work for the remodel before the painters can
start, just the portion of work that impacts the painters.
The “Install counters”
task can’t start until the “Paint” task has finished. By setting up this
finish-to-start dependency, you avoid getting drips of paint all over
the shiny new countertops. This type of dependency is most commonly used
in project plans.
The “Install new floors”
task can’t finish until the “Paint” task has finished. The painters
begin by painting the ceiling in both the kitchen and dining areas, then
move on to painting the kitchen. After the kitchen is painted, the
flooring installers begin their work in the kitchen, while the painters
finish painting the dining room. The flooring team can’t finish its work
until the painters have finished painting the dining room. At that
time, the flooring team can finish its work by flooring the dining room.
In Project, this is represented as a finish-to-finish task.
Finally,
the “Install new appliances” task can’t start until the “Install new
floors” task has finished. This is another finish-to-start dependency.
Project represents these task dependencies on the Gantt chart using arrows between the tasks. Figure 2 shows how our example might look if we entered it into Project and set up the dependencies.
Adding Dependencies Between Tasks
In Project, dependencies
between tasks are recorded in the row for the second task in the
dependency. For example, if you are creating a dependency in which Task B
can’t start until Task A has finished (a finish-to-start dependency),
you would record the dependency in the row for Task B. When you record
the dependency, you indicate the task’s predecessor.
To quickly set
start-to-finish dependencies between tasks in your project, select the
rows for the tasks you want to link, and then, on the Task tab, in the ScheduleLink Tasks. group, click
If you want to set up other
types of dependencies, create gaps between tasks, or overlap tasks, you
can set up dependencies using the Predecessors column.
To set up a dependency between two tasks using the Predecessors column, follow these steps:
1. | In the Gantt Chart view, be sure the Predecessors column is displayed.
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If the Predecessors column is not displayed, scroll all the way to the right of the table portion of the Gantt Chart view and then click Add New Column. Click Predecessors
in the list that appears, to add the column to the view. You can click
and drag the column header to move the column to another location in the
table portion of the view.
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2. | In
the row for the second task in the dependency you’re creating, type the
ID number (located in the row header) for the first task in the
dependency in the Predecessors column. Also, indicate the dependency type.
For example, if you are creating a dependency between Task A (ID number
1) and Task B (ID number 2), you would type the following for each
dependency type:
- Finish-to-start— To indicate that Task B can’t start until Task A finishes, type 1 in the Predecessors column for Task B, as shown in Figure 3. Project assumes a finish-to-start dependency, by default, so you don’t need to include a dependency type abbreviation.
- Start-to-start— To indicate that Task B can start only after Task A has started, type 1SS in the Predecessors column for Task B.
- Finish-to-finish— To indicate that Task B can finish only after Task A has finished, type 1FF in the Predecessors column for Task B.
- Start-to-finish— To indicate that Task B can finish only after Task A has started, type 1SF in the Predecessors column for Task B.
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3. | If
one of your tasks needs to overlap another (known as “lead time”), or
needs to fall behind another (known as “lag time”) by a certain amount,
type this in the Predecessors column, as well:
- Overlap two tasks— To overlap two tasks, type a negative duration, or percentage, after the task ID number and dependency type in the Predecessors column, as shown in Figure 4. For example, if you want Task B to start one day before Task A is scheduled to start, type 1SS-1d in the Predecessors column for Task B.
- Insert a delay between two tasks— If
the second task needs a delay after the start or finish of the first
task, type a positive duration, or percentage, after the task ID number
and dependency type in the Predecessors column, as shown in Figure 5. For example, if you want Task B to start when Task A is 50% through its scheduled duration, type 1SS+50% in the Predecessors column for Task B.
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