Grout is an integral part of any tile installation. It is also frequently the bane of a DIY homeowner's existence because in some applications it can stain badly. Some manufacturer's recommend that the grout be sealed after installing it to help prevent this staining from occurring. That is not always necessary, however. Learn when you do need to seal your grout to help prevent future problems.
There are several different kinds of grout on the market. The most common and the oldest is cementitious grout. This is grout that is made primarily of portland cement. Like all cements it is porous and will absorb moisture if it is exposed to it long enough, leading to stains. Light-colored grouts are more likely to stain than dark grouts, but all grouts do have the potential to discolor over time. Cement-based grouts used on floors and in wet areas such as showers should definitely be sealed after installation. This prevents the grout from absorbing moisture, and therefore staining, if there are any impurities in the moisture that it absorbs.
Epoxy-based grouts are used less frequently than cementitious grouts because they are more difficult to work with and spread. Epoxy is recommended for use, however, with several types of glass tile installation and with some green marble tiles. Epoxy is formed through a chemical reaction when two resins are combined. When it finishes curing it is hard, durable, flexible and completely non-porous. It will not absorb moisture, and if installed properly, it will not stain. Because it is non-porous, any sealers simply sit on the surface of the grout. This may cause the sealers to peel unevenly over time, discoloring the grout. If you have epoxy grout installed with your tile, do not seal it.
Pre-Sealed Stain Resistant Grouts
Nearly all grouts produced today contain some level of polymers added to the cement. This makes the grout more flexible, even in color and less prone to cracking. Some manufacturers have taken this a step further and have started producing pre-sealed stain resistant grouts. These grouts are mixed with a special additive rather than water. They are more difficult to spread and install, moving similarly to epoxy grouts. When they cure, however, they are minimally porous and can resist staining. Darker colors are more likely to resist staining than lighter colors, and depending on the manufacturer, you may need to seal the grout again in several years, but not at the time of installation.
Grout and Tile Sealers
There are two basic types of sealer used on grout. One is a membrane-forming sealer that sits on the surface of the grout. It may alter the appearance of the grout, causing it to appear shiny. It may also peel or become cloudy over time. The second type is called an impregnating sealer. This same sealer can be used to seal stone tiles and polished porcelain tiles. If you have installed stone or polished porcelain tiles in your home, consider sealing your grout right along with the tiles on a yearly basis to protect them all at once from staining.