The Waterfall Model in software development remains relevant, particularly in outsourced projects that require structure, predictability, and thorough documentation.
This traditional SDLC model remains a reliable approach for many organizations that value clearly defined stages, formal sign-offs, and minimal surprises during the execution process.
In this guide, we’ll explore how the Waterfall Model works, when it makes sense to use it in modern outsourced software projects, and the key practices to make it successful in 2025.
New to SDLC? Start with our complete guide to the software development life cycle.
What Is the Waterfall Model in Software Development?
The Waterfall Model is a linear and sequential approach to software development. Each phase must be completed before the next begins, and there is little to no overlap between stages. It’s called “waterfall” because the process flows steadily downward, like water cascading over a series of steps.
Originally introduced in the 1970s, the model was popularized by its clarity and discipline. While modern development often favors flexibility, many industries and project types still rely on Waterfall for its rigor, structure, and predictability.
Key Stages of the Waterfall Model
The Waterfall Model typically includes the following six stages:
- Requirement Gathering
- Stakeholders define and document all requirements.
- This phase results in a detailed Software Requirement Specification (SRS) document.
- In outsourced settings, this is the most crucial phase for avoiding misunderstandings.
- System Design
- Architects and senior engineers design the software based on the SRS.
- Includes both high-level architecture and low-level module design.
- Design documents (HLD/LLD) guide the developers and are shared with the client for approval.
- Implementation (Development)
- Developers begin writing code based strictly on the design documents.
- No new features are added unless a formal change request is made.
- Integration & Testing
- QA engineers test the entire system for bugs, defects, and compliance with the original requirements.
- This is usually done as a separate phase after full development is complete.
- Deployment
- The final, tested product is released to the production environment or delivered to the client.
- Any minor issues discovered in real-world use are logged for future patches.
- Maintenance
- Post-deployment support begins, including bug fixes and system updates.
- No major changes are introduced unless a new version is planned.
Want to learn more about QA integration? Read: Understanding QA in the Software Development Life Cycle
When to Use the Waterfall Model in Outsourced Projects
The Waterfall Model may not be trendy, but it’s ideal for certain types of outsourced projects, especially when:
- Requirements are fixed and well-documented from the start.
- Client involvement is minimal after the planning stage.
- Compliance and formal approvals are required (e.g., government, defense, medical software).
- Budget and timeline must remain predictable.
Suitable Scenarios:
- ERP implementations with defined modules
- Legacy system replacements
- Healthcare, aerospace, and finance platforms
- Public sector software RFPs (Request for Proposals)
Benefits of the Waterfall Model
- Clarity and Predictability: Every stakeholder knows what’s happening, what’s expected, and when.
- Easy to Manage: Project managers can track progress clearly with well-defined milestones.
- Comprehensive Documentation: Because everything is documented upfront, maintenance and future upgrades are easier.
- Ideal for Fixed-Price Contracts: Waterfall supports outsourcing arrangements where deliverables and budgets must be clearly defined from day one.
Limitations and Common Pitfalls
- Inflexibility: Once a stage is complete, going back is expensive and time-consuming.
- Late Testing: Issues often emerge at the testing phase, when they’re harder to fix.
- Poor Fit for Changing Requirements: If your project is still evolving, Waterfall can become a bottleneck.
Related read: Agile vs. Waterfall in Outsourced Software Projects
Best Practices for Using the Waterfall Model in Outsourcing
To ensure success when using the Waterfall Model with external teams:
- Document Everything Early: Ensure detailed requirement specs, design documents, and test plans are shared and signed off.
- Set Clear Expectations: Define the communication protocol, delivery format, review cycles, and acceptance criteria.
- Use a Change Request Process: Scope changes should go through a formal process with impact assessments.
- Plan Reviews at the End of Each Phase: Validate outputs before moving to the next phase to reduce risk.
- Choose the Right Vendor: Work with outsourcing partners who have a strong track record of executing Waterfall-based projects.
Final Thoughts
While modern projects often lean toward Agile or hybrid methodologies, the Waterfall Model in software development remains a valuable approach, particularly in outsourced projects that demand precision, predictability, and regulatory compliance.
It’s not about using the trendiest framework—it’s about choosing the one that aligns best with your project scope, stakeholder expectations, and outsourcing strategy.
