Schedules, wireframes, sketches, copy documents, images, illustrations, and mockups are all pointless if they are not turned into reality by markup and code. Building a responsive site is in many instances an opportunity to assess and improve existing processes. When you are retrofitting an existing fixed-width site, the considerations are different than when you start a project from scratch. But you will still want to make sure you improve the way your site is built and maintained as much as possible. Ideally, you began thinking about the build of your responsive site at the same time you started planning and designing it, because all the different disciplines can and will impact on each other.