Increasing the use of timber as load-bearing structures in buildings is an important contribution in the efforts towards a more sustainable building industry. Fire safety requirements for buildings in Norway are given in the Building Regulations from 2017. The authorities have also developed a prescriptive guideline, with pre-accepted solutions that can be chosen to ensure that the building meets the requirements. However, there are no pre-accepted solutions for buildings taller than 3-4 floors. The fire safety for these buildings must be documented through an analytical approach. This can be challenging as the methods usually require documented or verified data as input. Such data are often hard to find, and their applicability to the building must be assessed. Data from other countries or for other types of structures might not be relevant or applicable. This guideline is therefore developed to collect and share knowledge on analytical fire safety engineering of timber structures for buildings where pre-accepted solutions are not given. The guideline aims to increase the fire safety engineers' knowledge and expertise, as well as improve the quality of the analyses. It can also contribute to a more harmonised approach amongst the fire safety engineers. The guideline describes methodologies for analytical fire safety engineering and refers to publications that can be relevant and useful. The methods described are given in the Norwegian standard NS 3901 Krav til risikovurdering av brann i byggverk (Requirements for risk analysis of fire in buildings), and SN-INSTA/TS 950 Fire Safety Engineering - Comparative method to verify fire safety design in buildings. The target group is consultants performing analytical fire safety engineering of buildings with timber structures, in Fire class 3 according to the Norwegian Building Regulations from 2017, including amendments dated earlier than 2023. The guideline is not a handbook with detailed descriptions, but gives recommendations on which methods, tools and data that should be used. References to publications with detailed descriptions are given. Analyses of buildings in the lower Fire classes 1 and 2 with deviations from the pre-accepted solutions can also be performed according to the recommendations given here. Extensive knowledge on the methods and experience in analytical fire safety engineering is a prerequisite for the use of the guideline. The main focus is the load-bearing timber structure, but conditions regarding safe egress and rescue, as well as fire spread, are also discussed. The main chapters describe methodologies for analyses, relevant analytical methods, fire scenarios and calculations of the energy from the fire load.