Some of the problems with grout lines absorbing water can be quite obvious and others, not so obvious. The first, and least obvious problem occurs when the appearance of the grout lines deteriorates and becomes pitted over time. The most obvious problem is when staining occurs from bacteria growing within the grout. In a typical shower, water enters and stays within the grout, never drying out completely because of the frequency of water exposure with daily use. In the initial stages, this is a relatively slight degree of absorption, but the continuous water exposure, low pH (soap/ shampoo), and warm temperatures, causes slow chemical changes in the structure of the grout. Slowly but surely, the minerals that compose the grout structure dissolve away, allowing the water to absorb ever deeper into its matrix. As the minerals dissolve, the natural alkalinity of the grout also reduces, to a point where bacteria can now survive and reproduce on it’s surface. As this chemical process of deterioration progresses, so does the bacteria growth, which helps to accelerate the loss of structural minerals within the grout. This deterioration eventually reaches a point where the grout effectively carries the water down to the mortar bed, at the base of the tile. Now bacteria can flourish throughout the entire grout matrix making grout cleaning efforts completely ineffective. Moisture can now penetrate behind the tile, which eventually compromises the mortar bed, and the substrate. This is a situation seen way to often; huge areas of black mold growing behind the tile and penetrating all throughout the drywall backer and the drywall crumbling because it’s saturated with water. This water will also expand and contract with changing temperature, causing more movement, which in turn causes further cracking of the grout, accelerating the structural decline of the entire assembly.

As well, you have all probably experienced your bathroom floor tile grout deteriorating because the grout sealing stage has been neglected. A tile floor is obviously a much less abusive environment than the shower wall, but it also stains and becomes impossible to clean, just for a different reason. The same process can occur as described above depending on the frequency of water exposure however, the primary problem with these grout lines are staining from exposure to dirt and grime. Initially, floor grout absorbs water just as well as the wall tile grout in the shower. The unique problem here is that whenever anyone attempts to clean the floor tile, the water they are wiping back and forth across the grout lines becomes dirty. This dirty water pools in the grout lines as they are cleaning, and absorbs into the porous grout matrix causing it to quickly stain. Because the dirty water is so deeply absorbed into the grout matrix, it becomes very difficult, if not impossible to clean without bleaching (which also deteriorates the cement bonds in the grout, by the way). The irony is, that the more fastidious one is about floor cleaning, the more discoloured and hideous the grout lines become. This downward cycle would be eliminated by grout sealing to begin with.