4 - Flammability tests for external cladding on buildings

Abstract

Publisher Summary An exterior wall fire usually results from an intense fire within the building and the building fire usually masks the exterior wall fire. Thus, it sometimes can be very difficult to distinguish between the contribution made by the building fire and that made by an exterior wall fire involving combustible cladding material. Exterior fire spread problems become increasingly more important as rapid fire spread from floor to floor can occur via combustible exterior claddings creating a hazardous situation for building occupants. Fire spread over combustible cladding has attracted the attention of researchers in recent years. Where fire engineering methods can be used, i.e., in a performance-based Building Code environment, little guidance is given and solutions rest with the specific fire engineer whose knowledge and experience is relied on to provide the complying solution. A reason for performance-based codes is to allow for innovative design and to enable new materials to be used. There are two aspects of external claddings that are important to fire safety: Ignition and flame spread of the cladding from an external source; Ignition and flame spread caused by fires from the building itself. The flammability of external claddings has been controlled mostly by the application of prescriptive regulations using the concept of non-combustibility as the main parameter. With the trend towards performance-based codes, and innovation in materials and construction, the previous approach was restrictive and so a search was made for alternative means of assessing external claddings for flammability. This chapter suggests that it would seem obvious that carrying out essentially a full-scale test would be a solution and is an ideal for many applications and materials.