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 design (FEED), detail engineering, construction and operations. These can be new facilities (greenfield) or modifications to existing facilities (brownfield). Weight management is necessary throughout operations, decommissioning and removal to facilitate structural integrity management (SIM). The provisions of this document are applicable to fixed and floating facilities of all types. Weight management only includes items with static mass. Snow and ice loads are excluded as they are not considered to be part of the facility. Dynamic loads are addressed in ISO 19904-1, ISO 19901-6 and ISO 19901-7. This document specifies: a) requirements for managing and controlling weights and CoGs of assemblies and entire facilities; b) requirements for managing weight and CoG interfaces; c) standardized terminology for weight and CoG estimating and reporting; d) requirements for determining not-to-exceed (NTE) weights and budget weights; e) requirements for weighing and determination of weight and centre of gravity (CoG) of tagged equipment, assemblies, modules and facilities; This document can be used: f) as a basis for costing, scheduling or determining suitable construction method(s) or location(s) and installation strategy; g) as a basis for planning, evaluating and preparing a weight management plan and reporting system; h) as a contract reference; i) as a means of refining the structural analysis or model.