Social Networking (SN) systems provide messaging facility as well as the ability to generate and share content in form of user profiles, photos, videos, reviews, ratings, etc. SN architecture is complex, as it covers numerous Web pages with various data types; profiles, instant messaging logs, photos, videos, etc. In addition, ubiquitous SNs enable access from portable devices and therefore require a lightweight, adaptable architecture to meet constraints in screen size, storage capacity and network download time. SN architectural design patterns are proposed to induce reusability and loose coupling, thus improve performance and adaptability. These patterns are derived from conceptual modeling of common SN functionalities found in literature. Five patterns are derived; `user profiles and friend list management', `messaging', `file sharing', `edit & post content' and `semantic services'. The patterns are validated by application on five large-scale SNs targeted at healthcare that showed better reusability, customizability and scalability, and reduced interdependence between SN subcomponents.