Fire Resistance of Multistorey Timber Buildings

Abstract

Tall timber buildings are becoming popular around the world. This paper discusses options for setting the level of fire resistance in multistorey timber buildings. Fire resistance of timber structures involves a paradox, because it is well known that heavy timber construction has excellent fire resistance in severe fires, but it is also well known that burning of wood has contributed to severe damage and loss of life in some fires. This paradox often leads to contradictory statements on fire safety in timber buildings. This paper summarises recent international reports and proposes a consistent method of deciding which parts of multistorey timber buildings need additional fire protection.

Modern fire engineering designs of steel and concrete buildings rely on full “burnout” of any fire compartment, with no fire spread and no collapse, through the full period of fire development and decay, after which the building can be repaired. For timber buildings, the achievement of burnout is less certain, because of the residual fuel which is always present in the large timber structural elements. Design for burnout may require full or partial encapsulation of the timber, which may not be acceptable to the building’s owners or architects if they have selected wood for aesthetic reasons.