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.
Find your center line: When you start tiling, you should find the center line and lay out your tiles accordingly from there. The center line can either dissect your center tile, or it can mark the grout joint between two tiles; decide which pattern you like best. Once you've found the center, use your plumb line to snap a chalk guideline to follow. You will almost inevitably have to cut some of the tiles to fit the wall space. These cut pieces should lay against the wall corners. With careful measurement, it is possible to pre-cut the tile before you lay it. This can be handy if you do not have access to a wet tile saw at your job site. But keep in mind that if your measurements are not exact, you may have to run down to the local tile store to use their saw. When making your measurements, factor in 1/8 inch for each grout joint. It doesn't seem like much, but those joints add up!
Laying the Slate - Using a plastic bucket, mix your mortar. Put water in the bucket first, then add the mortar gradually until you find the right consistency. A strong stick can be used to mix mortar, but a mortar- and cement-mixing drill attachment can save you a lot of elbow grease. Keep in mind that mortar is thick and it can burn up your drill. Make sure you've got a powerful drill if you're going to mix mortar with it. For laying tile on a wall, and especially if you are hanging larger tiles, mix the mortar slightly thicker than you might otherwise do. Add just enough water so that the mortar is mixed all the way through, but not so much that it is runny. When you hold a dollop of mortar on your margin trowel, turn the blade sideways. The mortar should cling to the trowel and only sag very slightly and slowly. Notch trowels come in various sizes, so choose the right one for the size of the tile you are laying. The larger the tile, the deeper notch trowel you should use, because a deeper notch trowel applies a greater amount of mortar. Using your notch trowel, spread the mortar on the portion of the wall where you are going to lay your first few tiles. A notch trowel typically has a notched side and a notched end, as well as a smooth side and end. For the first pass with the mortar, use the smooth side in order to apply a thick bed of mortar. The notched trowel is gauged so that when you are holding it at a 45-degree angle, just the right amount of mortar is allowed to remain on the surface. Hold the trowel at a 45-degree angle to the wall surface, and use the notched side or end in order to create a grooved bed of mortar. This is what you will lay the tile on.
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.
Use spacers and wedges to properly adjust the tile positions as you go. Spacers are sold in varying thicknesses, most commonly 1/8-inch. Lay your base tile on a couple of spacers in order to establish that first grout joint between the floor and the first tile's edge. Then use spacers as you work your way over and up in order to keep consistently sized grout joints as you work. Wedges are small, triangular nylon pieces that can be used to slightly adjust the space between tiles. Again, with a natural product like slate, you are likely to find pieces that are not perfectly square, along with other slight irregularities. In these cases, wedges are your best bet for creating a consistent, even look. Keep looking as you work, and make a point of stepping back every so often to be sure your grout joints are staying consistent and appear relatively straight. You have a fair amount of time to make adjustments as you work. Tile mortar sets relatively slowly. Adjustments can be made even up to a half hour after the tile has been set.
Grout Preparation and Grouting - Once you've got the tile all set, go over the wall with a wet sponge and utility knife, and clean up any mortar that may have accumulated on the slate's surface. Also, look for areas where the mortar may have squeezed up through the tile joints; these will negatively affect the appearance of your grout. Use the utility knife to remove as much of this excess mortar as possible. Allow the set tile to dry for 24 hours prior to grouting. In a plastic bucket, mix your grout. Add water first, then grout. Mixed grout should have the consistency of cake batter. If it is too runny, add more grout. Keep in mind when mixing grout that a little water goes a long way.
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.
With a bucket of clean water and a sponge, you are ready to rinse. This process involves using the sponge to remove any excess grout from the surface of the slate. The rinsing process will also even out the grout applied in the joints. Rinse several times, until all grout and grout haze has been removed from the slate surface. It is a good idea to rinse twice, then allow the slate to dry for 15 minutes. At this point, any haze or excess grout material should become apparent, and you can rinse once or twice more to get it all removed.
Sealing the Slate - It's a good idea to seal your slate. Sealing protects the product from potential staining and makes it easier to clean. In addition, there are sealer/enhancers that really bring out the striking variation and color inherent in a natural stone product like slate. Talk to your local tile retailer about the different sealing products available, and choose accordingly.
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.