To enable weight reduction of skin stiffened structures in aerospace applications they can be loaded in the post-buckling regime during service. However, to do this safely the fatigue delamination growth behaviour of post-buckled skin stiffened structures must be well understood. To this end, skin-stiffener separation of single stringer compression specimens with an initial delamination loaded in post-buckling has been investigated using the virtual crack closure technique. Both quasi-static and fatigue delamination propagation were studied using Abaqus FEA 2017. Two recently introduced fatigue delamination growth methods, the Constant Amplitude Fatigue method and the Simplified Fatigue method, were investigated. The methods were verified at the simple specimen level using double cantilevered beam and mixed mode bending specimens before they were used to predict delamination behaviour in single stringer compression specimens For the single stringer compression specimen a clear correlation has been observed between the local buckling of the delaminated stiffener flange and sudden delamination extensions, both under quasi-static and under fatigue loading.