After breaking a project down into distinct, actionable tasks within your work plan, your next critical move is determining how those tasks interconnect. This is the process of mapping task dependencies—identifying whether a task is reliant on another, and exactly how they influence each other’s timing.
Getting this right is the difference between a fluid, adaptable project plan and a brittle timeline that collapses at the first sign of delay.
The Two Laws of Task Connection
Many project managers fall into the trap of over-complicating their project maps by creating unnecessary, arbitrary connections. To keep your schedule lean and accurate, remember that a legitimate connection should only be driven by two rules:
This exists when it is physically or logically impossible to work on one task before another is completed.
- Example: You cannot assemble the roof of a building until the load-bearing walls are erected.
- Example: You cannot edit a book manuscript before it has actually been written.
This stems from the established processes, safety standards, or best practices of the organization running the project.
- Example: You cannot begin product development until the client formally signs off on the project specifications document.
- Example: A QA team cannot begin formal testing until a code freeze milestone is met, per company policy.
The Golden Rule: If a proposed connection does not strictly satisfy one of these two laws, avoid adding it to your schedule. Over-connecting tasks creates artificial rigidity.
The Resource Overloading Trap (and How to Avoid It)
A very common pitfall is linking two tasks simply because they are assigned to the same person.
Imagine you have a single painter assigned to paint an entire apartment. Because they are only one person, they can only paint one room at a time. It is highly tempting to link Room A’s painting task to Room B’s painting task in a linear sequence.
This is a mistake. Linking tasks based on human availability creates a nightmare during the tracking and control stages. If you later hire a second painter to speed up the project, you would have to manually comb through your entire project plan to delete those artificial connections.
The Solution: Keep the tasks independent in your logic network. Address the schedule constraint during the resource allocation stage using Resource Leveling—a software mechanism or manual process that automatically staggers tasks based on resource availability without hardcoding false dependencies into your plan.
The 4 Core Types of Task Dependencies
To map workflows accurately, you must utilize the right type of logical connection. In project management, there are four standard dependency types:
- Definition: Task B cannot start until Task A finishes.
- Example: You cannot start pouring the concrete floor (Task B) until the excavation of the ground (Task A) is complete. This is the most common dependency type used in project management.
- Definition: Task B cannot start until Task A has started. They can run concurrently once initiated.
- Example: A team can begin coding the software (Task B) as soon as the database architecture design begins (Task A), allowing both teams to work in tandem.
- Definition: Task B cannot finish until Task A finishes.
- Example: The documentation and user manual (Task B) cannot be finalized until the final software build (Task A) is completely finished.
- Definition: Task B cannot finish until Task A starts. (This is the rarest dependency type).
- Example: A legacy server system (Task B) must remain active and cannot be shut down until the new cloud server goes live and starts running (Task A).
Fine-Tuning with Leads and Lags
Real-world projects rarely fit into perfect, immediate transitions. To make your schedule mirror reality, you can apply Lags (delays) or Leads (overlaps) to any of the four connection types.
Example: After painting a room (Task A), you must wait 2 days for the paint to dry (Lag) before you can mount shelving units (Task B). This is expressed as FS + 2 days.
Example: If writing a 10-chapter report takes 10 days (Task A), the graphic designer can begin formatting the layout (Task B) 2 days before the writing completely finishes, as long as the first few chapters are ready. This is expressed as FF – 2 days.
Summary Checklist for Project Managers
- Hard Logic: Are sequential tasks linked because it is physically or logically impossible to do them any other way?
- Soft Logic: Are preferential links based strictly on documented organizational processes, safety standards, or quality policies?
- No Resource Links: Did you avoid linking tasks just because they are assigned to the same person? (Use resource leveling instead).
- Right Relationship Type: Did you use the correct logical connection (FS, SS, FF, or SF) to reflect how the work actually finishes or starts?
- Dynamic Compression: Did you look for opportunities to fast-track the timeline by changing rigid Finish-to-Start chains into parallel Start-to-Start or Finish-to-Finish relationships?
- Passive Waiting (Lags): Are passive, non-work wait times (like drying, curing, or approval windows) modeled as Lags (+ days) instead of inflating a task's actual work duration?
- Safe Overlaps (Leads): Where Leads (- days) are applied, can the second task truly start early using only a partial handover or draft from the first task?
- No Open Ends: Does every task have a predecessor and a successor to ensure the relationship logic automatically calculates dates if a delay happens?
- No Circular Logic: Is the network free of loops (e.g., Task A → Task B → Task A) that trap the schedule in a calculation error?
