This report describes the experiments conducted during the first phase of a multi-phase project designed to assess structure-to-structure fire spread for structures in the Wildland-Urban Interface (WUI). The experiments focused on quantifying thermal exposures from auxiliary structures, e.g., sheds. The effects of shed sizes, construction materials, fuel loading, and separation distance on the ignition of primary structures (residential dwellings) with no wind have been studied and reported. Preliminary structure …