## 3 Data Collected to Verify the Model  
In order to carry out the experimental verification of the model, which is based on the random forest algorithm and presented in Section 2, experimental and archival research was carried out (with the methods described in Section 2) on excessively wet and saline brick walls in two historical buildings. They are the Golden Gate in Gdansk (Pomerania, Poland) and a residential and commercial tenement house in Katowice (Silesia, Poland). Brief descriptions of these buildings and the research sites, together with exemplary photographs, are provided below. Tables 1 and 2 show the data sets that were obtained as a result of the tests conducted in both buildings for the purpose of verifying the RF model. Therefore, 18 sets of results were obtained from the Golden Gate building, and 17 sets were obtained from the tenement house. In accordance with the methodology presented in Section 2, each set includes seven parameters: the dimensionless parameter \(Y\), which describes the year of construction of the building; the two dimensionless parameters \(X_{D}\) and \(X_{M}\), which were defined non-destructively, and which describe the moisture content of the wall; the three parameters \(X_{C}\), \(X_{S}\), and \(X_{A}\), which describe the percentage of the molar concentration of the chloride, sulphate and nitrate salts in the wall; and also the reference parameter \(U_{m}\), which describes the actual mass moisture content of the wall (in percent). The obtained results of the \(U_{m}\) fall in the range from 4.97% up to 21.92%, so they can be considered quite representative. Tables 3 and 4 present selected descriptive statistics that characterize the collected data. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \multirow{2}{*}{**Data Set No. **} & \multirow{2}{*}{ \begin{tabular}{c} **Year of** \\ **(K)** \\ \end{tabular}  } & \multirow{2}{*}{ \begin{tabular}{c} **Dielectric Meter** \\ **Reading X\({}_{D}\) (\(\star\))** \\ \end{tabular}  } & \multirow{2}{*}{ \begin{tabular}{c} **Microwave** \\ **Meter Reading** \\ **X\({}_{M}\) (\(\star\))** \\ \end{tabular}  } & \multirow{2}{*}{ \begin{tabular}{c} **Chloride** \\ **Concentration** \\ **X\({}_{C}\) (\%)** \\ \end{tabular}  } & \multirow{2}{*}{\ \begin{tabular}{c} **Sulfate** \\ **Scencentration** \\ **X\({}_{A}\) (\%)** \\ \end{tabular}  } & \multirow{2}{*}{ \begin{tabular}{c} **Nitride** \\ **Wull U\({}_{m}\) (\%)** \\ \end{tabular}  } \\ \hline
1. & 1610 & 133.20 & 40.70 & 0.455 & 0.550 & 0.500 & 7.88 \\ \hline
2. & 1610 & 157.00 & 56.80 & 0.122 & 0.800 & 0.010 & 8.88 \\ \hline
3. & 1610 & 124.30 & 55.80 & 0.042 & 0. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Name of the**} & \multicolumn{6}{c}{**Parameter Symbol**} \\ \cline{2-7}  & \(X_{D}\) **(-)** & \(X_{M}\) **(-)** & \(X_{A}\) **(\%)** & \(X_{C}\) **(\%)** & \(X_{S}\) **(\%)** & \(U_{m}\) **(\%)** \\ \hline Arithmetic & \(150.31\) & \(64.41\) & \(0.135\) & \(1.147\) & \(0.190\) & \(9.83\) \\ average \(\bar{x}_{i}\) & \(167.3\) & \(87.3\) & \(0.42\) & \(1.600\) & \(0.500\) & \(16.28\) \\ value \(x_{\text{min}}\) & \(130.2\) & \(46.3\) & \(0.035\) & \(0.200\) & \(0.000\) & \(4.97\) \\ \hline Standard & \(13.05\) & \(11.42\) & \(0.098\) & \(0.568\) & \(0.196\) & \(3.22\) \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Summary of the selected descriptive statistics that characterize the data collected during the research conducted in the tenement house—grouped as parameters \(X_{D}\), \(X_{M}\), \(X_{C}\), \(X_{S}\), \(X_{A}\) and \(U_{m}\). \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Data Set No. **} & \multirow{2}{*}{ \begin{tabular}{c} **Year of** \\ **Construction** \\ **Y (-)** \\ \end{tabular}