The modern system of shipbuilding includes applying integrated hull construction, outfitting and painting (IHOP) of ship interim products, as opposed to the traditional manner of first constructing the hull blocks, then performing basic outfitting and finally painting, all separate of each other. Even though most shipyards apply some degree of integration of all trades during vessel construction, much work could still be better integrated. This paper analyzes and maps the present IHOP construction of a typical shipbuilding erection block in a real shipyard. Through the application of a Product Work Breakdown Structure (PWBS) and group technology, the degree of IHOP integration could be increased. This is demonstrated to be in compliance with the lean principles of improving flow and kaizen. The paper will suggest how the vessel construction could be become leaner through a value stream map, thereby decreasing both duration time and man-hours thus securing significant savings for the shipyard.