Caulking over grout may not be a very fond option to do so because caulking is strictly related to attaching easy materials like shower curtains, bathroom floors, and tiles. But, if you are thinking about attaching a bathtub to the floor of the bathroom then grouting is necessary. But, to do that, our experts prefer to get rid of the existing grout from the surface so that it is clear and can be used for caulking from scratch one.