Software maintenance is a key activity for supporting the evolution of existing software systems but in many cases they are considered time consuming tasks. In certain systems (e.g. Web applications), changes must be performed very often and the time to carry out the maintenance activities is very short. In such cases, the need to count with suitable software architectures able to support the dynamicity of changes or new requirements becomes a need for every software project. In this work we describe how we applied the MAP method for building the architecture of a webbased application of a Spanish insurance company. One of the goals of the company was to reduce the maintenance costs of the existing systems, which motivated to move to a product line approach and fostering the usage of reusable components. We describe a case study carried out in a Spanish insurance company to obtain a single architecture valid for several applications belonging to the same domain.