Slate tile is a natural, reasonably priced building material that can give your walls a distinctive and beautiful appearance. Applying slate tile to a vertical wall is a project that can be performed by diligent homeowners who don’t mind doing some planning, using some elbow grease and getting a little messy.
Create Your Layout - Determine the size and pattern of the layout. Slate tiles are available in a variety of different sizes, including 2-inch, 4-inch, 6-inch, 12-inch, 16-inch and 24-inch squares. On a vertical surface, you generally won't want to go larger than 12 x 12-inch tiles. Tile can be laid out straight or set on a diagonal. In addition, your layout could use a variety of different sizes. For example, you could do the bulk of the wall with 12 x 12-inch tiles set on a straight line, with a band of 6 x 6-inch tiles set diagonally. If you can, draw your complete layout. Graph paper can be very helpful for this project. Seeing the plan drawn out on a piece of paper is good for determining the amount of material you will need, and where your cuts will fall. In addition, it helps you visualize the finished project, and determine whether or not the layout you are planning in your head will really look good on the wall.
When working a vertical tile application, it is advisable to "back butter" the tile. This means using your margin trowel to apply a coat of mortar to the back side of the tile itself before pressing it into the mortar bed. This serves a couple of purposes. First, it creates a better bond, and second, it gives you a little extra play with which to match up tiles with varying thicknesses. With a natural product like slate, the thickness of each piece can vary -- sometimes dramatically.
Using your margin trowel and grout float, spread the grout over the surface of the slate. Use the grout float to push the grout completely into the joints. Once you've spread grout over a certain area, hold the grout float nearly perpendicular to the surface, like a squeegee, and scrape away excess grout material. This will save you a lot of time during the rinsing phase. If you are working a particularly large area, you should consider grouting a small area, then cleaning it completely, before continuing on. Slate in particular can really hold grout, and if the grout is allowed to dry on the surface, it can be nearly impossible to get off.
Allow the slate to dry for at least 24 hours prior to applying any sealers or enhancers. Moisture is the number one cause of failure when it comes to applying sealers. Follow the manufacturer's instructions. Some sealers are applied with a paintbrush, and others with rags or sponges. Follow the instructions carefully to get the desired finish for your slate.