The product work breakdown structure (PWBS) of a shipyard defines both the interim product breakdown and the work breakdown. Shipyards that have a well defined PWBS can effectively reduce man-hours by applying techniques of group technology and hull block construction method (HBCM). In this paper, a case study of typical double-bottom blocks of both a car carrier and a self-unloading bulker vessel designed in different shipyards, are analyzed. Since each shipyard applies a different interim product breakdown structure (PBS), a best practice tabular comparision demonstrates which PBS is better. The conclusion is that different shipyards under the same corporation should objectively apply best practice methods which recognize and apply what is best from one yard to the other yard and vice-versa. This will raise the competitiveness level of both shipyards.