Crane-lift planning is critical but challenging to ensure construction safety and efficiency for the installation of heavy components. It engages a group decision-making process that involves various stakeholders to exchange knowledge of crane capabilities, site characteristics, and operational feasibility. However, conventional planning methods based on drawings, animations, and standalone virtual prototypes are inefficient in enabling collaborative decision-making due to rigid visualization and inflexible interactions among different stakeholders. This paper aims to develop a collaborative heavy lift planning (Co-HeLP) system that engages crane suppliers, site managers, and crane operators in an immersive and shared environment for crane layout optimization and lifting simulation. Specifically, the system incorporates a multiuser networking unit to enable stakeholders to design crane-lift layouts concurrently and synchronize changes in real time for facilitating information-sharing and collaborative planning. In addition, a cross-platform virtual reality (VR) unit is developed to provide stakeholders with role-tailored interactions of crane allocation and first-person operation. Automatic feasibility checking is also formulated to assist stakeholders in appraising jib reach limits and loading capacities more efficiently. The system is demonstrated using a real-life modular building project that involves the installation of multiple bulky modules. To evaluate the system, two groups of industry practitioners from crane suppliers and main contractors conducted heavy lift planning using Co-HeLP, where their responses were collected using questionnaire-based surveys and interviews. Results show that the system is rated highly on automatability (0.77/1), collectiveness (0.81/1), and applicability (0.85/1), with the advantages of full-scale visualization and multirole interactions. This paper opens up new possibilities for stakeholders to jointly manage crane-lift constraints and build consensus on layout plans through a mutually interactive and role-independent shared environment. More broadly, the paper derives a generic multiuser VR mechanism to address fragmented coordination and inefficient knowledge transfer, thereby facilitating collective planning and management in construction.