The document specifies a method of determining the steel stresses in longitudinal bars at midspan of unloaded reinforced components made of autoclaved aerated concrete. At midspan of an unloaded reinforced component the concrete cover, the corrosion protective coating and part of the sourrounding AAC are removed from at least three longitudinal bars, taking care to disturb the internal stresses as little as possible. Then strain gauges are glued to the surface of the bars. The steel stress is calculated from the difference of the strain gauge readings taken a) when the bar is under stress while still being embedded in the component and b) when the bar is free from external stresses after it has been separated from the component.