The number of multi-storey timber buildings has increased during the last twenty years. Recent well-known fires in London, Dubai and Brazil, although not in timber buildings, have increased concerns regarding large fire spread and high damage fires. As timber is a combustible material, concerns have been expressed regarding property safety and it has been questioned whether fire damage is more significant in buildings with timber as the main structural material than in other types of buildings. This report includes a statistical study of data of fires in multi-storey timber buildings in New Zealand and an analysis of high damage fires that occurred in multi-storey timber buildings in the USA. The data from New Zealand showed no significant difference between share of fires that had flame damage out of the compartment of origin in (a) multi-storey timber buildings that were constructed in or later than 1992 and (b) other types of multi-storey buildings that were constructed in or later than 1992. Fires in multi-storey timber buildings that were constructed before 1992 spread more frequently to neighbouring compartments than fires in other multi-storey timber buildings constructed before 1992. Data of high damage fires occurring in multi-storey timber buildings in the USA indicated that outdoor fire spread is the most common cause for large fire spread. Additionally, the data indicates that high water damage is most often caused by fire service interference and is significantly less often related to sprinkler activation.

Based on the analysis of fire spread of high damage fires in the USA, guidelines are given in the report to limit (1) outdoor fire spread, (2) fire spread through cavities, and (3) fire spread directly from a fire compartment to a neighbouring fire compartment. A number of these guidelines were evaluated using a fire test of a two-storey timber structure.