The results of a linear stability analysis of a floating thin liquid layer with both sides open to air and internally split in two halves by a permeable, heated or cooled divider are presented. For the case of deformable open surfaces and varying thermal and mechanical divider characteristics the results refer to steady and overstable modes of convection, hence leading to surface waves. Results are also provided about the role of the Marangoni effect in exciting antisymmetrical/flexural and symmetrical/squeezing modes of vibration of the thin liquid layer.