This Digest is part of a suite of related documents containing guidance for the construction industry on structural fire engineering design. The intention is to produce performance based guidance that brings together fire engineering and structural engineering providing a framework within which designers are free to develop site specific solutions based on real performance criteria. The Digests contain information complementary to the existing and emerging fire engineering codes and standards. Each digest may be used in isolation or as part of the full integrated suite. This Digest introduces the subject, provides essential background information and places the information in the context of the existing regulatory framework of the UK building regulations. Tests on full-scale buildings have shown that complete structures generally perform better than isolated elements on which compliance with regulations is usually assessed. These results and complementary analytical methods have provided the information required for a performance based approach to the design of buildings subjected to fire. 6 pages.