Prefabricerade badrumsmoduler - Är det en effektiv metod och i vilka projekt passar det?

Sammanfattning: The housing shortage in Sweden means that a lot of focus is placed on finding new efficient methods that allow for a faster and more cost-effective construction. The type of industrial construction that was used in the so called Million Program in Sweden in the 60s and 70s was substandard in many ways and has given many Swedes a negative image of what industrialized construction and prefabrication means. The bathroom is a part of the home that historically has caused a lot of problems in Swedish buildings. Prefabricated bathrooms are a construction method that could allow for a more efficient construction production in comparison to a traditional site-built bathroom, while maintaining quality and standard. The purpose of this study is to examine whether prefabricated bathrooms are efficient or not, and in which type of projects they are suitable. With the aim of answering the research questions, a case study has been carried out including both a building project using prefabricated bathrooms and a project using site-built bathrooms. Data has been collected through observations during site visits, literature studies and interviews with actors within and outside the case study. For the interviews, people with relevant professional roles and experiences have been selected from three different construction companies in Sweden. Two different building systems, semi-prefabricated and fully prefabricated building system, have been studied in building projects where bathroom modules have been used. In the project with prefabricated bathrooms, where a semi-prefabricated building system is used, it was noted that the most critical activity was the curing of the concrete in the slabs. More specifically, since the modules are self- supporting and thus do not carry any loads, a higher concrete quality must be used to achieve sufficient strength in the slabs. Additionally, a recess must be made in the slab to make place for the module and its underlying drain pipes. The floor slab then needs to cure for 12 days between casting and assembly of the bathroom modules. This means that the construction project must include at least three stairwells at the same time, for the use of the crane to be efficient. The saving of time that the project resulted in through the use of prefabricated bathroom modules, occurred when the inside of the building was done as a result of the activities that were eliminated. The time of the frame-work was however extended because of the curing of the concrete. A saving of 3 resources, a craftsman, a tiler and a plumber, was obtained. Bathroom modules in combination with a fully-prefabricated building system meant the same saving of time and resources with the inside walls, but did not lengthen the frame-work process. Another advantage with prefabricated bathrooms, is an improvement of the work environment, since the amount of people, materials and work on the site is decreased. The many rules and requirements controlling the construction of site-built bathrooms are also not needed to take into consideration since the bathroom modules are type approved. The optional choices that can be made by the customers are limited in bathroom modules compared to on-site bathrooms. The customers can either not make any choices at all or the choices need to be made very early, in a stage when a lot of the apartments in a project have not even been sold yet. This is a reason to why prefabricated bathrooms are best suited in condominiums where the target group has less requirements on the apartment aesthetics or student accommodations or hotels. The method is not suitable in exclusive housing projects where the customers want to significantly influence the design of their homes.