Project Dependencies: Role, Types, and Examples

When creating a project schedule, it is crucial to identify and account for dependencies between tasks. In project management, dependency is defined as a relationship between two tasks in which the completion of one task is dependent on the completion of the other task.

Different types of dependencies can be identified in project schedules, and each type has its own set of implications for project planning and execution. 

This blog post will discuss the role of dependencies in project management, the different types of dependencies in project schedules, and offer some examples.

What Are Project Dependencies

Dependencies in project management are connections between tasks on a project timeline. These dependencies determine sequencing and resource delegation in every project.

Before we go into the different types of dependencies, here’s a crash course for the most important terms to know related to this stage of project management.


Constraints are project limitations—in essence, they can all be stripped down to three main restrictions:

  • cost
  • time
  • scope

Lead and Lag Time

Lead and lag time are durations that project managers can add between two tasks. Lead time is the duration in which the following task will begin before its preceding one ends, while lag time is when a project manager decides to push back the beginning of a task after another one ends (i.e., creating distance).

Critical Path

The critical path is the project timeline that project managers create to determine which tasks are mandatory and must be completed on time. In other words, it’s a schedule of project dependencies with no slack time or lag/lead times in between.

Types of Dependencies in Project Management

Logical (Casual) Dependencies

Logical dependencies are the usual project dependencies that project managers usually encounter. These dependencies reflect the sequence of tasks and their logical relationship to each other. You can think of them as “if this, then that” relationships between project tasks.

  • E.g., if you want to build a house from scratch, you need to lay the foundation first before building a wall.
  • Another way to look at it is through the project management process itself: when project managers are in the process of project planning and need to brainstorm for project ideas first before creating project goals, objectives, and milestones. They also have to complete a project charter to proceed with creating other documents such as the scope statement, risk register, and list of deliverables.

Resource Dependencies

Resource dependencies occur when a project task cannot be started or completed until the required resources become available. These dependencies are restricted by cost, time, or the overall scope of the project (constraints).

  • For example, if you’re an event planner and need to book a band for your upcoming wedding, you can’t start contacting bands until you know how many guests will be attending.  If you have a limited budget and can only afford one band, then it depends on how many guests are attending.
  • In project management, an example can be teams waiting for project managers’ approval of their project deliverables.

Preferential Dependencies

In the case of preferential dependencies, some tasks are given a preferred status over others—when project managers prioritize project tasks by using a must-do, should-do, and nice-to-do approach.

  • For example, your planning team may have planned for an outdoor event but is dependent on the weather. If it rains, the team may need to quickly move indoor activities such as the band and catering setup.

Sequential Dependencies

Sequential dependencies are project dependencies that must be completed in a specific order. These types of dependencies can often be found in project processes where tasks are divided into smaller work packages with multiple steps. Once project managers complete a project task, they can go to the following project deliverable.

  • For example, if you want to bake a cake from scratch, you should follow the recipe step by step and in order. If not, your cake may end up tasting quite differently than what was intended.

External Dependencies

External dependencies are project dependencies that come from outside of the project. They can be caused by factors such as natural disasters, changes in government policy, and supplier failure.

E.g., if you’re a construction manager and a supplier doesn’t deliver the correct materials on time, it will delay your project timeline.

Project dependencies can be a cause of project delays and should be taken into account when planning projects.

Which Types of Dependencies Are Most Common in Project Schedules

FS [Finish-to-Start]

FS refers to project tasks that require project managers and their teams to complete one task before they can move on to the next. This is the most commonly used dependency in project management.  It’s when project managers finish a project task before they start another one.

  • For example, if you want to paint your bedroom, you should get all of your painting supplies ready first before starting with any part of the room, such as prepping furniture or cleaning surfaces.

FF [Finish-to-Finish]

FF project dependencies are where two project tasks are required for completion at nearly the same time or within a specified period from each other. It’s when project managers finish two project tasks simultaneously or soon after one another instead of finishing one before starting on the next task.

  • For example, if you want to paint your bedroom, it may be best that you complete all of your painting supplies like priming surfaces and cleaning brushes as well as painting each wall. You can also set a specific amount of days in between each task so that they can dry properly before moving on to other project tasks such as applying coats of paint.

SF [Start-to-Finish]

SF project dependencies are tasks that require project managers to start one project task first before completing another project task. This is an uncommon type of dependency in project management because dependencies can often be completed in any order.

  • For example, you may want to shampoo and condition your hair before styling it. In this case, the shampooing must begin before the conditioning.

SS [Start-to-Start]

SS project dependencies are where two project tasks are dependent on each other, starting at nearly the same time or within a specified period from each other. This is the least common type of dependency in project management.

It’s when project managers start two project tasks simultaneously or soon after one another instead of finishing them first before starting on the next project task.

  • For example, if you want to paint your bedroom, it may be best that you start prepping furniture and cleaning surfaces at the same time instead of finishing it first before starting on another project task like applying coats of paint.  You can also set a specific amount of days between each project task to dry properly before moving on to other project tasks.

When Should Project Managers Use Dependencies?

Project managers should use project dependencies when planning project work to understand how project tasks are connected and which project tasks must be completed first before starting other project tasks.

By understanding the logic of it, you’ll also be able to see what a delay might mean for your project timeline and whether there are types of dependencies that may not make sense.

Example: Project Dependencies in Construction Management

In construction management, projects often involve external factors such as suppliers, local government policies, weather conditions, or natural disasters.

These external factors can cause delays because the project manager has less control over them than their internal colleagues or team members who help deliver the project on time with minimum defects. In this case, it would make sense for project managers in construction to use project dependencies to plan their project work.

Example: Project Dependencies in Product Development

In product development, projects often involve multiple stakeholders and team members who may have different views on the final product.

This can cause delays because project managers need consensus from everyone involved before making decisions that impact how long it takes them to deliver their project or if something doesn’t meet expectations during delivery.

In this case, it would make sense for project managers in product management to use project dependencies to plan out when things will be ready so that there aren’t any surprises later down the line by using logic behind what needs to be done first before other project tasks.

Project Dependencies: Conclusion

In project management, dependencies are an essential part of the process. By understanding the different types and how they work, you can better manage your projects and ensure that everything is completed on time and to specification. This article looked at the role of dependencies, three common types, and some examples of each type.

While there are other types of dependencies out there, these are some of the most commonly seen in project management. As always, if you have any questions or need help planning your project, don’t hesitate to reach out to a professional.