This document specifies requirements for managing and controlling the weight and centre of gravity (CoG) of offshore facilities by means of mass management during all lifecycle phases; including conceptual design, front end engineering, detail engineering, onshore/inshore construction, and offshore installation. These facilities can be completely new installations (Greenfield) or the modifications to existing installations (Brownfield). It is also necessary to continue managing and controlling weight throughout operations, decommissioning and removal to facilitate Structural Integrity Management (SIM) and to assist with removal of facilities during decommissioning. The provisions are applicable to offshore facilities of all types (fixed and floating). Only items with mass shall be addressed. Loads not related to mass shall be omitted. Se ISO 19904-1, ISO 19901-6 and ISO 19901-7. Weights from mass of snow and ice are not to be included as they are not part of a facility. This document specifies: a) managing and controlling weights and CoGs for components and entire facilities; b) managing weight and CoG interfaces; c) standardised terminology for weight and CoG estimating and reporting; d) requirements for determining Not To Exceed (NTE) weights and budget weights; e) weighing and determination of weight and CoG of tagged equipment, major assemblies, modules and facilities; This document can be used as a basis for: a) costing, scheduling or determining suitable construction method(s) or location(s); b) planning, evaluating and presenting the client s, contractor s or fabricator s weight management and reporting system; c) as a contract reference between client, contractor and suppliers; d) as a means of refining the structural analysis or model.