As an answer to the challenge for managing the complexity of offering greater product variety, firms in many industries are considering platform-based development of product families. Key in this approach is the sharing of components, modules and other assets across a family of products. Current research indicates that companies are often choosing physical elements of the product architecture (i.e. components, modules, building blocks) for building platform-based product families. Other sources for platform potential are widely neglected. We argue that for complex products and systems with hierarchic product architectures and considerable freedom in design, a new platform type, the system layout, offers important commonality potential. This layout platform standardizes the arrangement of subsystems within a product family. This paper is based on three industry case studies, where a common layout could be defined for a product family based on a modular product architecture. In combination with segment specific variety restrictions, this supports the effective, efficient and flexible positioning of a company's products. The employment of layout platforms can lead to substantial complexity reduction and thus serve as a basis for competitive advantage, as it imposes a dominant design on a product family, improves its configurability, and supports effective market segmentation.