Facility management deals with all activities that are not core business for a company and are consequently outsourced to specilized companies. Maintenance is a fundamental activity in facility management and it is often handled by Global Maintenance Services (GMS) where some maintenance activities are delegated by the company to service providers and are remunerated according to measurable results expressed as Key Performance Indicators. In this context, it would be desirable to have information systems trustable by all involved actors. In this paper, we discuss the design of a blockchain solution capable to support a GMS on-chain. We first introduce the GMS concept and how it is related to the Principal-Agent relationship, then we show a reference architecture to implement GMS on-chain. We discuss a use case of on-chain GMS in a hospital showing how smart contracts and oracles can be used in this context. We present the advantages of this approach and we discuss the open problems for realizing a proof-of-concept.