The Grand Canal was designated as a UNESCO World Heritage Site in 2014. The Alan Guild hall, as an important canal cultural relic, also became a world heritage site. The last maintenance work was done here over fifteen years ago in 2001. The buildings have visible damage, particularly the purlin beams in the south of the central room of the rear hall. Accidents can happen at any time. There was an urgent need for repair work this year. According to the regulations for protection of cultural relics, repair work should maximize preservation of the building units, following the principle of maintaining current status and minimal intervention. Therefore, a method that would not damage the roof ridges was adopted when the purlin beams and the rear gold column were replaced. This minimal intervention method was successful. It is a new approach by the Ningbo municipal government to maintenance of ancient building beams and critical columns.