Hydrometallurgical refineries for cobaltCobalt and nickelNickel productionProductions have historically been built using stick-built construction methods, especially for primary extractionExtraction. The concept of using modularModular (ex-works) construction is gaining traction in chemical processing plantsProcessing plant. This construction method, or a hybrid thereof, is becoming increasingly popular. This is especially true for refineries located in remote areas where local specialized labor is scarce and in mini-refinery applications, which lend themselves to circular economy and recyclingRecycling types of projects. Examples include Northvolt and First CobaltCobalt. The research examines the advantages and disadvantages of modularModular and stick build approaches. ModularModular construction involves assembling prefabricated modules off-site and transporting them for on-site assembly. Conversely, stick-built relies on on-site construction using conventional methods. The analysis delves into aspects such as cost, time and skills availability, offering insight into the selection criteria for the various construction approaches. Unit operations that lend themselves to modularity are highlighted in the paper, including most tanks, mixer-settlersMixer-settler for solvent extractionSolvent Extraction (SX), certain thickeners and reagents. These units are identified as conducive to modularModular construction, contributing to improved assembly efficiency and reduced on-site work and risk. Analyses are conducted to establish the capital cost cross over point at which site constructed systems become more economical than an equivalent modularModular system as large plants are recognized as less amenable to modularity due to their substantial size. The study provides a technoeconomic analysis comparing costs and time between traditional stick build and modularModular approaches. This analysis aims to provide insights into the economic viability of these construction methods. Furthermore, the study addresses the time and cost implications associated with on-site work, offering a nuanced understanding of the efficiencies and drawbacks of each approach in this critical phase of hydrometallurgical refinery facility construction.