###### Abstract  
The paper presents the results of the verification of the neural method for assessing the humidity of saline brick walls. The method was previously developed by the authors and can be useful for the nondestructive assessment of the humidity of walls in historic buildings when destructive intervention during testing is not possible due to conservation restrictions. However, before being implemented in construction practice, this method requires validation by verification on other historic buildings, which to date has not been done. The paper presents the results of such verification, which has never been carried out before, and thus extends the scope of knowledge related to the issue. For experimental verification of the artificial neural network (ANN), the results of moisture tests of two selected historic buildings, other than those used for ANN learning and testing processes, were used. An artificial unidirectional multilayer neural network with backward error propagation and the algorithm for learning conjugate gradient (CG) was found to be useful for this purpose. The obtained satisfactory value of the linear correlation coefficient R of 0.807 and low average absolute error \(|\Delta\mathsf{f}|\) of 1.16% confirms this statement. The values of average relative error \(|RE|\) of 19.02%, which were obtained in this research, were not very high for an in-situ study. Moreover, the relative error values \(|RE|\) were mostly in the range of 15% to 25%. The effect of long-term excessive moisture and salinity in a wall is its susceptibility to frost destruction over time and the falling off of plaster. This is followed by the chipping of brick and mortar fragments, which gradually reduces the wall's cross-section and decreases its strength. In order to stop the above-mentioned destructive processes, it is first of all necessary to perform tests aimed at determining the amount and causes of the moisture. Of all the known methods for testing the humidity of brick walls, the most reliable results are obtained when using the destructive direct gravimetric method [11]. It allows the moisture value to be determined on the surface of the tested partition, as well as in its thickness. When using it, however, it is necessary to collect in-situ samples of material for laboratory tests. In the case of historic buildings, masonry sampling for moisture testing is only possible to a very limited extent. Paper [12] highlights the fact that destructive methods are not suitable for historical buildings of great architectural significance and also that nondestructive testing methods play an important role in the diagnostics of these buildings. Of the nondestructive methods, electrical methods such as the dielectric, resistance, and microwave methods are considered to be very useful and are commonly used for testing brick wall moisture [15; 16; 17; 18]. When conducting tests using these methods, it is not the humidity that is directly measured but instead a different physical feature of the wall. The value of this feature is affected by the water that is contained in the wall. Therefore, in the dielectric method the phenomenon of changing the dielectric constant of the tested material due to moisture is used; in the resistance method the change in material resistance depends on the amount of water it contains; while in the microwave method the attenuation of microwaves passing through moist material is measured. The measurement result when using these methods is the unnamed parameter \(X\). Therefore, in order to determine the moisture value, it is necessary to scale the apparatus on the tested object and determine the correlation relationship \(U_{m}\)-\(X\), in which \(U_{m}\) usually means mass humidity. For this purpose, a specified number of moist masonry samples should be taken, and their mass humidity should be determined using the gravimetric method. The obtained humidity values should then be correlated with the corresponding readings of the meter that was used for the testing.