On April 6 1999, Sinclair co-founded Architecture for Humanity with Kate Stohr, a charitable organization which developed architecture and design solutions to humanitarian crises, and provides pro bono design and construction services to communities in need.
In 2006, Sinclair and Stohr published a compendium on socially conscious design, titled Design Like You Give A Damn: Architectural Responses to Humanitarian Crises (May 2006, Metropolis Books).