Purpose: This work is based on the problem with the product cross-laminated timber and its properties in the event of fire. The reason for the problem is the glue used in the product and the lack of requirements for adhesion at high temperatures. Due to this, there is a risk of delamination in the event of a fire, i.e. that the wooden slats that constitute the largest component in the CLT wood fall off during the course of the fire and contribute to extra energy. Method: The work is built up of two different methods, first a literature study and then an experiment. The literature study focuses on the National Board of Housing, Building and Planning's building regulations, the production of cross-laminated timber and what happens in the event of a fire. The experiment was carried out at Fågelbacken in Västerås, where help from the rescue service was available. The informative part of the report begins with a subject reference framework where the first part consists of information about the National Board of Housing, Building and Planning's requirements and ordinances that are based on the Planning and Building Act and the Planning and Building Ordinance. This study describes the experiment, everything from the application of the fire protection treatment to the design of the fire test. The materials included in the fire test are described and any certifications they hold are mentioned. The results section presents the results of the literature study and the fire test. Results: The four pieces of wood showed different results after fire, as three out of four showed cracks between the slats on the fire-affected surface. No piece of wood delaminated or had loose slats, however, the cracks are interpreted as meaning that the glue did not withstand the temperature that the fire generated, and melted. The depths of the carbon layer, on the other hand, were significantly protected by the fire protection treatment as there was a maximum difference of 7 mm between one of the fire protection-treated pieces of wood and the untreated piece of wood. The burning time of the fuel pool varied. The course of fire for the pieces that were treated with fire protection was strong with large flames and large, black smoke pillars. Conclusion: The conclusion of the thesis is that the fire protection treatment has a good effect on the depth of the carbon layer, which delays the risk of delamination. The fire protection treatment also has a good effect on the adhesive in some of the cases when no or few cracks between the slats were seen.