This paper discusses how building commissioners in the Low Countries operated to obtain the best quality in form and construction when they commissioned a building to a contractor. In the Low Countries, building contracts have been used since the late fourteenth century and in many of them the quality of materials and constructions were prescribed. Municipal regulations and guild regulations were important in ensuring the quality of the construction, but despite these general provisions and statutory inspections, building commissioners usually inserted extensive clauses in contracts, which related to the quality of wood, stone, brick and other materials. Based on the investigation of approximately 250 building specifications and contracts dating back to before 1650, this paper shows how the development of quality descriptions for brick, stone, wood and other products changed over time. For carpentry and stone, known quality specifications date back to the end of the fifteenth century. Quality requirements for brick masonry date from the sixteenth century while for other materials they don’t appear until the end of the sixteenth century. Contracts also included provisions regarding force majeure and unforeseen circumstances. These provisions could relate to ambiguity in the wording of the contract as well as to procedures in case of sickness or death of the contractor. However, this did not prevent disputes, which on some building projects lasted for decades.