Semi-destructive and non-destructive techniques are not commonly used for masonry as they are complex and difficult to perform. This paper describes validation of the following methods: semi-destructive and non-destructive, ultrasonic technique for autoclaved aerated concrete (AAC). The research subject was the compressive strength of AAC test elements with declared various density classes of: 400, 500, 600 and 700 (kg/m3) and various moisture levels. Empirical data including the shape and size of specimens, were established from tests on 494 cylindrical and cuboid specimens, and standard cube specimens 100×100×100 mm using the general relationship for standard concrete (Neville’s curve). The effect of moisture on AAC was taken into account while determining the strength fBw for 127 standard specimens tested at different levels of water content (w = 100%, 67%, 33% 23% and 10%). Defined empirical relations can be used to correct the compressive strength of dry specimens. For 91 specimens 100×100×100 mm, the P-wave velocity cp was tested with the transmission method using using the ultrasonic pulse velocity method with exponential transducers. The curve (fBw – cp) for determining the compressive strength of AAC elements with any moisture level (fBw) was established.