This thesis examines how historic records of repairs can inform service life estimations and preventive conservation planning for historic structures. After a discussion of service life and preventive conservation, this thesis extracted and analyzed historic mentions of repairs in the record books of the Concord School House in Germantown, Philadelphia, Pennsylvania, which span from 1775 to 1987. Repairs to the building’s masonry, carpentry, windows, finishes, and roof assemblies were chosen for investigation. Data collected included the length of time between repairs and the recorded prices of repairs. The prices of repairs were converted into 2013 dollars and used as an indicator of the size of repairs and a means of comparison between repairs in different time periods. Ultimately, this thesis found that data from historic records of repairs was not specific enough to stand alone in estimating service lives of the building systems for use in preventive conservation planning. However, analysis of the historic records identified repair cycles which, when supplemented with conditions assessments, could be used to inform preventive conservation planning and the formation of building reinvestment plans. Investigation of historic repair records also revealed the importance of long-term, consistent care in preserving historic structures, and the need to conceptualize repair plans in terms of centuries rather than human lifespans.