In the present paper, experimental results are presented for the characteristics of liquid/vapor interface and liquid height under stratified-wavy flow conditions, including purely stratified flows and intermittent flows characterized by long flow lengths of stratified-wavy flow separated by short liquid plugs. Convective condensation experiments were performed for R134a, R600a, R290, and R1270 in a 9.43 mm internal diameter channel. Data were obtained for the liquid height, waviness characteristics (i.e., roughness), and interfacial wave velocity at mass velocities ranging from 50 to 300 kg/m^²s and saturation temperature of 35°C. The measurements were obtained from analysis of flow images recorded at an acquisition rate of 25000 fps. The results revealed that the average local liquid heights evaluated from the tube bottom varied from 0.8 mm to 3.4 mm and the wave velocities for stratified flows are within the range of 0.6 and 1.8 m/s. The average liquid height value decreases as the mass velocity decreases and the vapor quality increases. The wave velocity decreases with the vapor quality decrease. Besides, the wave velocity tends to increase as the average liquid height and the liquid phase velocity increase. The average liquid height reduces as the modified Froude number increases, probably, due to the progressive predominance of inertial forces due to the effects of increasing the gas velocity. Average interfacial surface roughness, given in terms of Ra (EN ISO 4287), from 0.18 to 0.5 mm were observed.