Lay Out the Backsplash
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Wall tiles are typically thinner and lighter in weight than floor tiles. Many are made with built-in spacer on their edges, also known as lugs (image 2). If your tiles don't have lugs, ask your tile dealer for the proper size plastic spacers. Using spacers between the tiles will help maintain the proper gap and prevent the tiles from slipping downward before the adhesive sets up. The mastic will not adhere to the spacers; they can easily be removed and discarded before the joints are filled or grouted.
The backsplash space between a countertop and wall cabinets usually can be filled with two or three horizontal tile rows, depending on the size of your tiles. Because tiles create a grid-like pattern, try to choose tiles that fit this space — wall installations look better when they are vertically even and symmetrical from end to end. Bull-nose or edge tiles of various sizes are also available to finish edges, fill gaps or to avoid having to cut tiles to fit.
Check that the countertop is level. If it is not, stand a tile at the lowest spot and mark a level line on the wall at the tile’s top — this will be your starting point. Use a standard level or laser level to extend this reference line across the wall and around the entire area that is being tiled (image 3). The tops of all tiles in the bottom row must meet this line or be cut (from the bottom) to line up with the mark. Tiles installed above this line will not require cutting. If you are tiling all the way up to the cabinets, place the cut tiles or uneven gap just below the cabinets where it won't be as noticeable.
To ensure a symmetrical layout from end-to-end, measure and mark the center point of each area being tiled. Before you apply mastic and begin tiling, do a dry run by lining up the edge of one tile with the center mark, then place tiles side by side to determine how many tiles will be needed and the width of the end pieces (image 4). Don’t forget to include spacers between each tile, if required.
If the end pieces will be very small or odd-sized, you may be able to adjust the spacing slightly to avoid having to cut the ends. If this does not work, repeat the dry run but place the first tile directly over the center mark, which may enable you to cut equal-size end pieces, often from a single tile. If one side of your tile work will have exposed edges, use whole tiles near this edge and cut only the tiles that end at the wall.
If you are tiling over painted drywall, use course-grit sanding sponge to rough up the surface. This will help the mastic adhere better to the wall. Wipe off the dust and debris with a damp rag.