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.

Timber is one of the most common materials that had been use for a long time. The need for new buildings will affect the climate negatively, that is why it’s necessarily to find new ways to build quickly and sustainably. Cross-laminated timber (CLT) product came in the 1990- century. The material was developed to be used in high residential wood constructions buildings. The material considered to have good properties compared with other types of wood material, some of the studies showed the possibilities of building high residential with the CLT material. Such high rises buildings work best when CLT wood constructions combined with other materials, which called, Composite constructions. Case study preformed theoretically in Fullriggaren building in Alderholmen in Gävle city, the building have 14 floors and about 40 m high. With the purpose of trying to investigate the consequences that occur when the concrete floor slabs were replaces  with CLT wood floor slabs, taking into account the rules and standards for fire safety, acoustics, oscillations and vibrations. In order to achieve this and to determine the most suitable alternatives, the different types of CLT-wood floor slabs was compared. The building studied in its design and execution, and a simpler model created in Revit 2018. The challenge was that the building has a long span of maximum 10 m. The different types of CLT floor slabs which compared in the study was, CLT timber joist slaps, flat floor slab and CLT wood floor slabs in combination with steel hat beams and other beam steel types. Each type of floor slabs had its advantages and disadvantages, but the results and studies showed that timber and concrete composite floor slab combined with steel hat beams are the best possible options for the construction in Fullriggaren building, where the floor slab height is the shortest compared to other CLT wood floor types. With the chosen floor slab, the problem of vibration and oscillations will minimize. When using such a floor slab, the building height will increase, which means in this case, removing an entire floor from the building. / Trä är ett av de vanligaste material som har används sedan länge i byggkonstruktioner. Behovet av nya byggnader kommer att påverka klimatet på ett negativ sätt, därför är det bra att bygga snabbt och hållbart. Korslimmat trä (KL-trä) är en produkt som kom under 1990-talet. Trämaterialet utvecklades där den kan användas i träkonstruktioner i flervåningshus.Materialet anses ha goda egenskaper jämfört med andra typer av trämaterialen, litteraturstudier visade på möjligheten att bygga högt med KL-trämaterialet. Liknande höghus fungerar bäst när KL-träkonstruktioner kombineras med andra material s.k. Hybrida konstruktioner. Fallstudien utfördes teoretisk i  Fullriggarenbyggnaden i Alderholmen i Gävle, som består av 14 våningar och är ca  40 m högt. Syftet var att undersöka konsekvenserna som uppstår när betongbjälklaget ersätts med KL-träbjälklag, hänsyn tas till regler och normer när det gäller brandsäkerhet, akustik, svängningar och vibrationer. För att uppnå detta och kunna bestämma lämpligaste alternativ, jämfördes olika typer av KL-träbjälklag. Byggnaden undersöktes beträffande konstruktion och utförande, och en enklare modell skapades i Revit 2018. Utmaningen var att byggnaden har långa spännvidder med max 10 m. Olika typer av KL-bjälklag jämfördes som kassettbjälklag, samverkanbjälklag, plattbjälklag och KL-trä bjälklag i kombination med stålhattbalkar och andra ståltyper. Varje typ av bjälklag har sina fördelar och nackdelar, men resultatet och studierna visade att samverkabjälklag kombinerad  med stålhattbalkar är den bästa lösningen för konstruktionen i Fullriggaren, då dess tvärsnitthöjd är den minsta jämfört med andra KL-träbjälklagtyper. Med det valde  bjälklaget minskas även problemet med vibrationer och svängningar. Vid användning av detta bjälklag kommer byggnadshöjden att ökas, vilket leder till att  en våning måste väljas bort.