Open Building is an approach to the implementation of large projects designed for change. Design tasks are separated. One prepares a shared architectural or urban infrastructure. The other provides the design of fully independent ‘territories.’ Utility systems follow this separation. The approach has several advantages: decision flexibility for developers; added long-term value and sustainability because of built-in capacity for adaptability; and opportunities for new business formations delivering integrated infill in both new projects and conversions to new uses. Open Building is represented in the United States by the Council on Open Building (www.councilonopenbuilding.org) and in the Netherlands (www.openbuilding.co).