WorkSafe have put together a guide to PCBUs (Persons Conducting a Business or Undertaking) working together
These guidelines are for Persons Conducting a Business or Undertaking (PCBUs) who are sharing a workplace with other businesses, or are working as part of a contracting chain.
They provide advice on how you can meet your duties under the Health and Safety at Work Act 2015 (HSWA), illustrate different contractual relationships between parties, and provide examples of ways you can build health and safety into contract management.