How to Seal and Grout Slate Tile: A Guide with Tips and Suggestions

The process of filling and finishing slate tile is known as grouting. Grouting is a relatively straight-forward process when compared to the other work that goes into laying a slate tile floor, countertop, or shower wall. From an aesthetic point, of view grout beautifies and enhances tile work whether you are working with slate or another type of stone. From a more practical viewpoint, it is the final necessary step in sealing tile.

If you choose to seal your slate tile, it is a good to use a polyurethane sealer that is water-based and able to slightly penetrate porous stone for added protection. This is especially important when installing your slate tiles in an area that will be exposed to fluctuating moisture levels and humidity, such as a mud room, bathroom (in particular the shower area), or kitchen areas, such as around the kitchen sink. This will also apply to kitchen countertops and splashboards where slate tile may be selected or chosen over other decorative materials.

When your sealant has cured, it is time to apply the grout. Grout can be purchased in various weighted sacks depending on how much you have calculated you will need. It is available in powdered form which mixes readily with water to a recommended consistency according to package specifications. It is also available as a premix which works well for smaller projects. Besides grout, other supplies and implements you will need are as follows: a grout trowel (also known as a rubber float) assorted sponges and towels for clean-up afterwards; and, if needed, a padded surface or knee pads for floor-work comfort while applying the grout. If you are grouting tiles above your shoulder area, safety glasses are recommended.

Once your grout is as ready as you are, it is time to begin. The first thing you should do is make sure that the valley between your slate tiles is clean and free of all loose dust particles and debris as this may hinder adherence of the grout.

After you have cleaned the area, take up the grout mixture on your trowel and apply grout diagonally while holding your trowel at an approximate forty-five degree angle. Begin this process in a small area at first, and when one section is finished move on to the next. When you have packed the material into the joints at an appropriate level, turn your trowel to a right angle (ninety degrees) and remove the excess grout.

Then take one of your loose towels or sponges and gently wipe the loose grout off of your slate tiles to expedite later clean-up. You do not need to scrub intensely, only remove immediately visible and accessible excess grout present on the tiles.

After your grout has completely dried and set, take a fresh towel and sample a small area in a remote corner of your tile work and verify that your grout has, in fact, fully set. If it has, then take your larger sponges and towels and scrub the entire surface of your slate tile installation to remove any and all leftover grout on your slate surfaces. Keeping this process in mind as your work progresses will greatly reduce the amount of clean-up time needed at the end of the project and eliminate hardened splotches of grout. At this point, you can apply an additional coat of sealant if desired.

After this coat of sealing has set, you are ready to enjoy the fruits of your labor for years to come.