This is Steve from SKG Renovations, providing you with some important information on the nature of tile and grout, and the importance of grout sealing in a typical tile installation.

Grout Sealing; so important yet often overlooked

As a contractor in the business of renovation, I have personally completed many tiling jobs and observed many more. Because of this, I believe I have good insight into some of the important details that are often overlooked by tilers. One of these important overlooked details, is grout sealing. I believe that it is one simple extra step, that can ensure that the beauty of your grout lines and the integrity of your tiling assembly as a whole, can last for years to come. In my experience, most people do not take the small amount of extra time to seal the gout lines after a tiling job. I would say that about 90% of both professional, and DIY jobs that I see, neglect this very important step. That is why I felt that it was important to emphasize the importance of grout sealing in this post.

Problem of Porosity

Especially in a shower enclosure or tub/shower surround, where the surrounding tile is exposed to continuous water exposure, the importance of grout sealing cannot by overemphasized. Many people do not recognize that the grout lines are not simply a decorative margin that helps define the tile borders, but also a structural assembly including the tile, mortar and grout. The grout secures the tile matrix together by providing a very hard and inflexible filler between the tile gaps due to it’s high cement concentration. This high cement content helps to stiffen this matrix, but also aids in the bonding between the grout and the tile edge. This strength and rigidity is considered necessary because it becomes part of the finished surface that will be exposed to water, abrasion, and dirt. Although grout is extremely strong and resistant to abrasion, expansion and contraction, it’s serious limitation is it’s porosity. And it is a problem that gets worse over time.

The process

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 i have seen far too often; huge areas of black mold growing behind the tile and penetrating all throughout the drywall backer and the drywall crumbling in my hands 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.

Floor Tile Grout

As well, you have all 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. And 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.


I think I have made it quite clear how a beautiful and expertly installed tile installation can be affected so negatively over time, simply because the tiler made no attempt to reduce water penetration into the grout lines, simply by grout sealing. Ask your tile supplier to recommend a good quality grout and stone sealer. Cost does vary considerably, but I would recommend to avoid the low cost ones because their ability to seal, and their longevity, are usually related to their price. I regularly use AquaMix Sealers Choice Gold. Keep in mind that even with the best grout sealer, you should still allow a day or two ever year or two, to re-apply the sealer. You will see when the grout seal begins to fail when water exposure causes it to darken slightly. Performing this simple step will keep your tiles surfaces looking like new, for decades to come.


There is a relatively new trend in the manufacturing of tile grouts which involves the use of acrylic (plastic-like) compounds within the grout, rather than relying only on the traditional bonding agent, Portland cement. This trend has developed in order to solve the porosity problem with traditional tile grout. The result is actually quite impressive in my opinion. Some of you may have heard the term “epoxy grout” which is the name often used to represent this new class of grouts. The blends can be quite varied and the explanations about how one compares to another can indeed be quite confusing. Suffice it to say that this is great new trend with some impressive product offerings out there. I would suggest that before you attempt to use any grout that is described as “epoxy grout”, that you instead look for grouts that use the term “pre-sealed” instead. These products include acrylics in their formulas so that your grout is sealed as soon as it cures. That means, no more grout sealing, and no more staining and deterioration. Because of the acrylic solvents in these types of grouts, they do involve a slightly different application technique, and take some practice to gain some proficiency; “epoxy grout” being the most difficult of the group. My new “go-to” pre-sealed grout is  Mapei Flexcolor CQ. It is as easy to use as you could expect from these types of grouts, and it dries hard as a rock, and most importantly….. it’s water proof ! I can’t really comment on how long it will continue to resist water, but I am happy with it’s performance thus far.

Happy Tiling !!

Check out some of my other informative posts

Also check out some of my Kitchen and Bathroom projects, …… and my tiling prowess, of course (skg-renovations.com).