Adequate building maintenance can prolong buildings’ life span, reduce expense of new construction, but it is also an ever-going unpredictable expenditure for schools. To estimate maintenance expense of a building becomes an important task in school management and campus planning. With record of 10 year primary school new construction and maintenance contract documents, and data of school and building ages, the expense of building maintenance throughout a building’s life cycle is investigated. To further inquire new construction expense and maintenance expense of a school, the formula between school age, new construction expense, maintenance expense and average building age of a school is induced, which can be important reference for a school to predict annual construction expense, and for education authority to review annul budget distribution. Since maintenance expense goes up with building age, to maintain an old building may not be an economic decision compared with starting a new building. By combining new construction and maintenance expense of a building throughout its life span, the most economic life cycle of a school building is acquired, which can be critical information in school management and campus planning.