The report is about a research programme "Timber construction and fire". The aim of the project is to illustrate the possibility of calculating the fire resistance of building panels and wall constructions. In an increasing number of countries, fire classification of elements of construction which is based on analytical treatment instead of the results of furnace tests in accordance with ISO 834 is beginning to be permitted. In Sweden, analytical fire engineering design of loadbearing and separating constructions as an alternative to design on the basis of standardised thermal action in accordance with ISO 834 has been approved for long time. The fire resistance in test and in the calculated model shows good agreement. In wood based boardes the difference in 1 minute, and in wall constructions it is normally not more than 10 minutes.