--- title: "Task dependencies: types and the critical path | attendo" description: "What task dependencies are in a project, the four types with examples, lag and lead, what the critical path is and the mistake of not writing them down." url: "https://attendo.me/en/glossary/task-dependencies" lang: "en" --- # Task dependencies: the four types and the critical path Also known as: Finish-to-start · predecessors Task dependencies are the rules that tie the start or finish of one task to another, such as painting not starting until the plaster has dried. ## The four types - **Finish-to-start**: B starts when A finishes. The most common: you do not paint until the plaster is dry. - **Start-to-start**: B starts when A starts. Site layout and safety signage begin together. - **Finish-to-finish**: B finishes when A finishes. The installation documents are closed out with the final tests. - **Start-to-finish**: B cannot finish until A starts. The rarest: the old equipment keeps running until the new one starts up. Each one can have a **lag**, such as waiting two days after pouring concrete, or a **lead**, such as starting to paint when the plaster is half done. ## The critical path Chaining dependencies together reveals the **critical path**: the sequence of tasks where every day of delay is a day of delay on the handover. Tasks outside it have slack. Knowing which is which tells you where to put people when something goes wrong. ## The usual mistake Keeping dependencies in the project manager’s head. If they are not written into the plan, moving one date does not move the ones that depend on it. And the [Gantt chart](https://attendo.me/en/glossary/gantt-chart) shows a schedule that is no longer possible. ## In attendo The [Gantt chart](https://attendo.me/en/modules/gantt-chart) supports all four types, each with a lag or lead in days, and reads the same business calendar as the schedule and deadlines. The sequence is written into the [project](https://attendo.me/en/modules/projects) plan. - [attendo Projects](https://attendo.me/en/projects) ## Where it is used in attendo ### Modules - [Gantt chart](https://attendo.me/en/modules/gantt-chart): Plan projects and construction jobs with dependencies and a baseline - [Projects and construction](https://attendo.me/en/modules/projects): Jobs and plant shutdowns with line items, progress and live cost ### Industries that use these modules - [Energy and renewables](https://attendo.me/en/industries/energy-renewables) - [Contractors, construction and engineering](https://attendo.me/en/industries/contractors) - [Consulting and professional services](https://attendo.me/en/industries/professional-services) - [And any other business](https://attendo.me/en/industries) ## Related terms Projects ### Gantt chart Project timeline · schedule chart A Gantt chart is a project schedule drawn as bars: each task takes one row, and its bar starts and ends on its planned dates. Projects ### Baseline Project baseline · schedule baseline A baseline is the saved copy of a project’s approved plan, with its dates and durations. It lets you compare what was planned with what is actually happening at any time. Projects ### Resource utilization Team workload · utilization rate Resource utilization is the share of each person’s available hours that is already committed to planned work, measured by day, week or month. ### On the blog #### Project baseline: spot the drift while you can still fix it Almost every project drifts. The problem is finding out at the wrap-up meeting, when there is nothing left to fix. A baseline lets you see it in week two, not in the final week. 4 min read [See all 53 glossary terms](https://attendo.me/en/glossary) ## Shall we look at it with your data? We will show you how what you just read works in attendo, with your own assets, tickets and customers. If it is not a fit, we will tell you. - With your operation, not a generic demo - A real person from our team replies - No cold calls afterwards Would you rather talk first? - Phone [+34 910 053 530](tel:+34910053530) - Email [sales@attendo.me](mailto:sales@attendo.me) - Monday to Thursday 9:30 AM to 6:30 PM and Friday 9:30 AM to 2:30 PM (Spain time)