Wood construction has increased in the recent years for apartment buildings consisting of four to five floors. Compared to other building materials, wood has great environmental benefits. For a building in a larger scale constructed in wood, cross-laminated timber, also known as CLT is an option. The technology for CLT originated in Sweden during the 1990s and since then the development has increased. CLT has excellent stiffness and strength properties. The design of a floor in CLT is important for how the building and the environment are perceived indoors. The wooden floor is about five times lighter than concrete, which means that measures are required to meet the sound requirements set by Boverkets building regulations in Sweden. This will affect the span. The aim of the project is to present a knowledge overview of CLT and for floor in CLT up to 9 meters in span, to compete with concrete floor in steel and prefabricated concrete frames.

The study includes a quantitative methodology using three different data collection methods. These are literature study, document analysis and calculations. The literature study and the document analysis are based on scientific-and research articles, together with manuals. The calculations are carried out in Stora Enso's calculation program Calculatis by Stora Enso. The program follows Eurocode's design principles.

The result of the study shows that a CLT-board with laminated beams gives greater span than just a CLT-board does. The calculation means that the plate must meet the deflection requirement L / 300. Research shows that construction with CLT is increasing and there is great potential to obtain a cost-effective reduction of the carbon footprint and at the same time improve the utilization of natural resources by replacing non-renewable building materials such as concrete and steel with CLT. In order to achieve the sound requirements that are established, the CLT floor must be dimensioned thicker and measures such as additional insulation.

By looking at the results, the conclusion is drawn that CLT-floor may grow further to compete with concrete floor in the future. Currently the material is considered useful and environmental for smaller constructions for such as smaller houses, due to the sound insulation problem. For larger constructions with the similar problem can timber-concrete composite be an alternative. CLT-floor reinforced with glulam beams may be considered as a choice for larger and bigger constructions because the span widths increase, and the construction can withstand maximum deflection.

The study is limited to mainly considering CLT but also a small amount of concrete and glulam. Vibrations and environmental risks such as moisture, sunlight and fire, are not considered. The calculations the work uses are based on Eurocode 5, dimensioning of wooden structures. Other types of design principles have been excluded.