A software architecture description facilitates the comprehension, analysis and prototyping of a piece of software. However, such a description is often monolithic and diffi- cult to evolve. This paper proposes a framework, named TranSAT (Transformations for Software ArchiTecture), for incrementally integrating new concerns into a software architecture. The structural and behavioral properties of a new concern are represented by a self-sufficient component assembly description, called an architecture plan. TranSAT proposes a software architecture pattern as a means of integrating business and technical plans. Such a pattern includes not only the plan to integrate but also the preconditions that the target architecture must satisfy, and the modifications to perform on this architecture. Consequently, from a set of patterns, TranSAT allows a software architect to incrementally build complex architectures.