This book investigates the bending behaviour and long-term creep response of ancient timber beams, combining historical analysis with modern experimental research. It opens with a study of wooden beam mechanics during the Modern Age (1492–1815), tracing the evolution of sizing methods, resistance mechanisms, and fracture morphology. Failure modes are explored through multiple in situ case studies, examining how species, defects, grain orientation, and environmental conditions influence crack initiation and propagation. A classification system of failure causes and sequences is proposed, offering valuable insights for the conservation and structural assessment of historic timber structures. An extensive experimental campaign on eighteen 19th-century roof beams characterizes their material and mechanical properties, including the assessment of defects, through both non-destructive and destructive testing.The long-term loading study—rare in its scope worldwide—reveals deformation trends and supports predictive modelling of timber behaviour under sustained stress. By bridging historical knowledge, in situ observations, and laboratory research, this work provides engineers, conservators, and researchers with practical tools for understanding, preserving, and strengthening historic timber structures.