Waterfall model
Splits a project into six phases run in order: Requirements, High-Level Design, Low-Level Design, Implementation, Verification, Maintenance. The next phase does not open until the current one closes, and a closed phase is locked.
Register nowWhen to use it?
- Work where the requirements are known up front and will not change along the way.
- Projects needing approvals and documentation, where each phase must be on record.
- Work where the order itself matters: production must not start before design is finished.
Step by step
- 1Write the project name at the top and press Start.
- 2The six phases stack up. Only the open phase accepts items; later phases are marked with a padlock.
- 3When the phase is done, press the "complete this phase" button under the box.
- 4After you confirm, the next phase opens; the completed one gets a tick and its items can no longer be changed.
- 5A project can hold several waterfall projects.
Keyboard shortcuts (desktop)
Tips
- There is no button to reopen a phase; if you completed one by mistake, undo is the only way back.
- Make sure a phase is genuinely finished before closing it — closing locks the text as well.
- If requirements will shift along the way, waterfall boxes you in; WBS or PDCA works more comfortably there.
Worked example
Example: delivering a reporting module to a bank
Scope fixed by contract, delivery date fixed, written sign-off from the client at the end of each stage. Work like this moves through the stages in order.
Requirements
- Report types listed
- Permission rules written
- Client sign-off obtained
Design
- Data model drawn
- Screen wireframes
- Performance limits agreed
Build
- Reporting engine
- Permissions
- Export
Test and hand over
- Internal testing
- Client acceptance testing
- Go live
- User training
Both the strength and the weakness of waterfall are visible here: because the scope is fixed up front, progress is easy to measure — but a requirement that changes during the build sends the whole plan backwards.
Frequently asked questions
What is the waterfall model?
A method that splits a project into sequential stages and does not start one before the previous one is finished: requirements, design, build, test, delivery. It is named after water falling down a set of steps.
Waterfall or agile?
If the scope is known up front and unlikely to move, waterfall carries less management overhead — construction, regulatory work and fixed-price delivery all fit. If the scope will only become clear as you go, waterfall gets expensive and agile methods fit better.
Can you go back to an earlier stage?
You can, but it costs, and the model is not designed for it. If you are going backwards often, that is a sign the scope was never clear enough up front — at which point the real question is whether waterfall was the right choice.
What happens between stages?
Each stage ends with a deliverable and a sign-off, and the sign-off should be written. The entire guarantee waterfall offers rests on both sides agreeing, at the same moment, that a stage is closed.
Is it free?
Yes. Klarsti is free and ad-free right now, and you do not need an account to run a waterfall project.