Welds have an associated residual stress field that affects the propagation rate of weld zone defects/cracks. Crack propagation modifies the local stress field through residual stress relaxation, changing the crack driving force. As crack propagation affects structural integrity, knowledge of residual stresses and their relaxation is of significant value. In this work the strain field (and hence stress) around defects and cracks in a low carbon steel butt weld will be measured using the ENGIN-X strain scanner. Three fusion line defects, parallel to the welding direction, with the same profile but of different depths will be investigated along with equivalent cracked samples and a defect free region. Each set of defects simulates the progressive extension of a crack. The results will quantify the relaxation of the stress field around weld zone defects/cracks due to their propagation.