Software Architect's Handbook

Disadvantages of the bottom-up approach

A bottom-up, or emergent, approach, assumes that change is cheap. Agile methodologies and practices provide an approach that anticipates change and can adapt to it. However, depending on the nature of the change, refactoring software architecture design can be very costly.

A bottom-up approach, with no initial architecture, can lead to lower levels of maintainability. With the refactoring that may be necessary with this approach, issues can arise. If the team is not diligent, this problem can become worse over time.

The entire scope of work may not be known when using this approach. This makes it more difficult to plan and estimate the entire project, which may be unacceptable for enterprise software. ...