Utvecklingsbehov av Enhetstider i Ny- och Ombyggnadslistan: Monteringstid vid Användning av Självborrande Skruv i Massivträstomme

Sammanfattning

Introduction: The construction of buildings with massive timber structures has become increasingly common in Sweden over the past 15 years. Although the building method has gained popularity, it is still considered relatively new, and both working methods and fastening techniques are continuously evolving. In ”The Swedish Construction Time List” which presents estimated time requirements for various construction activities, has not kept pace with these developments concerning massive timber structures. As a result, construction companies working with this type of structure lack established guidelines for cost estimation and production planning. Instead, they are often forced to rely on their own experience and approximate time requirements. Aim: The aim of this study is to investigate whether the construction industry requires specific unit times for the assembly of massive timber structures and to compile the time needed for pre-drilling and screwing various screw dimensions. Method: A mixed-methods design was applied, combining a real-time case study with experimental data collection, with an overall emphasis on qualitative analysis. The case study included several interviews with individuals holding different professional roles within the project, using interview guides tailored to each person's role. The experiment was carried out with the aim of investigating how different screw dimensions, with varying physical conditions, affect the time required for assembling massive timber structures. Results: The findings demonstrate clear variations in installation times depending on screw dimension, angle of insertion, and execution method. Both interview data and experimental measurements indicate that these factors have a direct impact on production planning and cost estimation. The results suggest that the current version of The Swedish Construction Time List does not adequately capture the realities of assembling massive timber structures, particularly regarding fastening operations with larger screws, angled connections, and tasks requiring pre-drilling. Conclusion: The study concludes that The Swedish Construction Time List is only partially applicable to modern timber construction. While certain activities may be comparable to existing entries, there is a pronounced lack of specific unit times for fastening operations using self-tapping screws. The findings highlight a need for revised or supplementary unit times to ensure more accurate planning and cost estimation. This research therefore provides an empirical foundation for the development of standardized time values in contemporary timber construction.