The waterfall model: classic project management explained simply

Timo Gerhardt, Tuesday 23 August 2022 | Reading time: 10 min.

The waterfall model embodies classic project management. A linear structure is formed by strictly successive phases.

The waterfall as a classic approach for projects

In the run-up to a project, a decision must always be made as to which method is most suitable for the specific case. Here, the project manager is spoiled for choice. Some of the most common methods are, for example, the critical path method, Kanban, Scrum or Scrumban, which combines elements of the two previously mentioned methods. These approaches all fall into the category of agile methods.

On the other hand, there are the classical methods. These are defined by a holistic approach. This means that a concrete end state is defined at the beginning of the project, which must be achieved in the course of the project. One of the best known concepts in this context is the waterfall model.

Most people who have been involved in a project in some way have probably heard of this method, which is considered one of the most established. In order to show what is behind this widespread concept, we will introduce you to the waterfall method in the following article. We will also explain how you can profitably apply this method to your projects.  The project management solution from InLoox can generate additional added value here.


Definition: What is a waterfall model?

The waterfall method is a linear model. It is composed of different phases. Only when one phase is fully completed the process moves on to the next. Since it is a classical method, the necessary information from all stakeholders is gathered before the project starts. As a result, the various interests are united in a common goal. Based on this, a sequential project plan is designed.

It is defined exactly which work steps are included in which phase, also exact start and end points are determined. As a result, errors in the implementation are minimized as far as possible. Due to the high efficiency, the structuredness and finally the precise way of working, the waterfall method still enjoys great popularity even in a time when agile project management is on everyone's lips.

The 6 phases: How does the waterfall work?

The sequential project plan usually consists of 6 phases, which are shown in the following graphic. Progress here only flows in one direction, just like in a real waterfall.

The waterfall model: classic project management explained simply

In the first two phases, the requirements for the project are defined and analyzed. The aim here is to comprehensively determine what is to be achieved in this project. The more precisely the requirements for the project result are recorded in the project plan, the higher the probability of success. The first steps are therefore already decisive in determining whether the project will be a success or ultimately threatens to fail.

Subsequently, in the design phase, the requirements are translated into specifications, which are consequently aggregated into a first draft.

In the subsequent construction phase, a first prototype is created based on the design.

This prototype is then tested for the first time and it is checked whether the newly developed concept meets the requirements.

Finally, after all tests are completed, the result of the project is delivered to the customer and put into operation. Although further tweaks and updates can be made during this phase, it is the final stage of the waterfall methodology.

The top-down approach

A key feature of the waterfall methodology is the top-down approach. This manifests itself in a strictly linear procedure. This means that the next phase is not started until one phase has been completed. Since it is a document-driven model, a corresponding report is created after each phase, which can be viewed by all project participants if possible, and which records essential aspects such as progress or problems in detail.

What are the advantages and disadvantages of the waterfall model?


  • High planning reliability
  • Easy to understand
  • Clear deadlines and costs can be enforced
  • Traceable project progress
  • Simple planning, control and documentation


  • Late error detection, since the test phase only takes place at the end of development
  • Lack of flexibility due to rigid planning
  • Lack of feedback loops
  • Not universally applicable

Application in practice

In practice, the waterfall method is mainly used in areas with relatively stable environmental conditions. If short-term project-relevant changes, for example in markets, in politics or with regard to technical developments, are largely excluded, this method is very suitable. In this way, it is possible to avoid having to modify the project afterwards. This requires a flexibility that this method cannot offer.

Originally, the method was developed for construction and production processes. In this area, the waterfall model is still used today. Such projects are characterized by a high degree of structuring and constant requirements. The described work steps can usually be carried out strictly in the specified sequence. In the case of generic construction and production processes, environmental conditions, apart from the volatility of material costs, are often of secondary importance and the agreed goal is always clear.

This method is also very popular in the IT industry, mainly in the area of software development. Especially in small, simple and clearly structured software projects, the waterfall model is considered promising due to its simplicity and straightforwardness.

In principle the methodology is applicable and goal-prominent in almost each range for projects, if certain conditions are fulfilled: The project should be plannable in detail in its entirety and allow linear processing. The common goal should also be clear from the beginning, as should the requirements and specifications. Fixed structures, traditional decision-making channels and a low probability of adjustments that become necessary afterwards additionally favor the use of this project management methodology.

Die Wasserfallplanung

The extended waterfall model

The waterfall model can be extended in principle by enabling jumps back in the project flow. As a result, the method is no longer strictly sequential, allowing for greater flexibility. For example, it is easier to implement changes into the project at a later stage. In addition, iterations allow errors that are discovered later to be corrected directly in the phase in which they occur. Thus, problem resolution does not just address symptoms. Instead, the problem is fixed in its origin.

Since a rigid and linear approach hardly meets the requirements of an increasingly fast-moving world, the extended waterfall model seems to make more sense in most cases. It combines the advantages of the classic model with greater flexibility.

The waterfall method vs. agile project management

As already mentioned, the waterfall model is one of the classic methods of project management. In contrast to this, there are a large number of agile methods that are becoming increasingly popular in everyday project work. Scrum, Kanban and Co. are characterized in contrast to the classical methods by a fundamental flexibility and adaptability thought. Two characteristics are of central importance for agile project management: On the one hand, the procedure is always incremental. This means that separate and fully functional individual parts are created during the development process and later aggregated into an overall result. On the other hand, iterativity, i.e. an implementation of feedback and repetition loops, is of great importance. In this way, an optimal solution is continuously approached.

In this case, there is no such thing as an optimal solution for all projects. It is true that agile working is on everyone's lips, while classic methods are often dismissed as outdated and losing importance. However, in order to handle a project in the best possible way, it is unavoidable to evaluate the project conditions and decide on an exactly suitable method based on this. For example, it may be the case that for the construction of a prefabricated house, a classic solution is appropriate, while in automotive development, the advantages of an agile approach come into play.

Regardless of the type of project you are facing and the methods you use for it: Your project will definitely benefit from project management software that meets your needs. Find out which benefits you will enjoy with InLoox's project management solution and which added value will be created for your project.

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