Grout is often overlooked in the cleaning routine. Yet these cracks between stone tiles deserve at least as much attention. Stained grout can spoil the appearance of an expensive wall or floor treatment. Even worse, dirty grout can breed mold, mildew and bacteria, which can lead to more trouble and expense -- and possibly even illness.
Like tile, grout is best cleaned with moderately alkaline cleansers. Make a runny paste with baking soda and water, and gently scrub with an old toothbrush or other soft-bristled brush. If you detect fungus growth, knock it out with a thicker mixture of three parts baking soda to one part bleach. Rinse either mixture with plenty of water and dry well. You might consider using a wet/dry vacuum for large areas of floor.
Next, learn how vinyl wears many faces in the bathroom, and how baking soda helps keep them all clean.