During the 1990s, the Getty Conservation Institute (GCI) carried out a major research and laboratory testing program-the Getty Seismic Adobe Project (GSAP)-to develop effective retrofit methods for historic adobe structures. In April 2006, the GCI hosted the GSAP colloquium which concluded that its methodology was reliable and effective, but its reliance on high-tech materials and professional expertise was a deterrent to its wider implementation. In response to these conclusions, the GCI initiated in 2009 the Seismic Retrofitting Project (SRP) with the objective of adapting the GSAP guidelines so that they better matched the equipment, materials, and technical skills available in Peru. As part of the SRP implementation phase, the GCI developed construction documents for two of the four prototypes: the Church of Kuño Tambo and the Cathedral of Ica. The current paper describes how a principles-based approach helped the team to take decisions on suitable retrofitting techniques while preserving the authenticity of each of these sites and how this methodology could be applied to develop retrofitting project for similar sites in other seismic regions.