As the first federally designated and protected archaeological preserve in the United States (1889-92), the site of Casa Grande Ruins National Monument in Arizona, USA, provides an excellent opportunity to examine the effects of past site conservation and management policies. Renewed investigation and analysis of the caliche building material and wall conditions of the Casa Grande using new techniques of field, laboratory and digital recording have allowed a reassessment of the structure in an effort to explain recent phenomena of alteration and deterioration, and make recommendations for structural and surface monitoring and treatment. The focus on the development of a detailed condition survey of the earthen structure has also promoted the creation of a standard graphic lexicon of earthen building conditions for use at other sites.