Waterfall runs a project as a sequence of phases that each finish before the next begins: requirements, then design, then build, then test, then release. Its defining assumption is that you can know the requirements well enough up front to plan the whole thing.
The one thing it is good at
Predictability, when the requirements really are knowable. If you are migrating a known system to a known target by a legally fixed date, a sequential plan with a signed spec is easier to price, staff and report on than an iterative one. Plenty of construction and regulated work runs this way for good reasons.
The specific way it fails on software
Feedback arrives at the end. You find out whether the thing was right after it is built, which is the most expensive possible moment to find out. And because the plan was signed, every discovery becomes a change request instead of a course correction - so people stop raising them, and the built thing quietly drifts from the useful thing.
Most teams are somewhere in the middle
Very few real projects are purely one or the other. A common and honest shape is a fixed-scope commercial agreement with iterative delivery inside it: the contract names the outcome and the exclusions, and the team works in short cycles to get there. That works if - and only if - the exclusions were written down and changes get priced as they arrive.
Frequently asked questions
Is Waterfall always the wrong choice?
No. It is the wrong choice when requirements will change and you have pretended they will not. Where they genuinely are fixed, its predictability is an advantage.
Can we do Waterfall with a client and Agile internally?
Many teams do, and it is workable as long as the commercial agreement names its exclusions clearly and there is a real change-order process. Without those two things you have taken on all the risk of both approaches.
How Spectr helps
Catch scope creep while you can still do something about it
Out-of-scope work flagged as it comes up, with a decision recorded on each one
Related terms
Spend less of the week on documents
Spectr drafts the spec, the requirement document and the stories from your meetings. You review and approve.
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