Barrows Hall is one of the busiest buildings at the University of California, Berkeley campus. The building has eight floors of academic spaces shared by thirteen different departments. The rehabilitation and seismic strengthening concept developed by murakami/Nelson incorporated thick steel--reinforced concrete walls which bookend the east and west ends of the building and collector beams at each floor that tie these two masses together. By adopting the exterior strengthening approach the building was occupied throughout construction and by adding new elements to the exterior, the façade was transformed.