Tiling Over A Laminate Countertop, continued

Setting the Tile

The first step in preparing a bonding bed of thinset over the Ditra is to use a flat steel trowel to completely fill the square recesses in the surface (Figure 3). Once I've filled the mat, I add more thinset and spread it with a 1/4-inch square-notched trowel.

Figure 3.Once the tile layout has been fine-tuned (top), more thinset is troweled into the waffle-patterned surface and onto the exposed edges of the countertop, which were previously stripped of their laminate self-edging (bottom).

As in applying the thinset bed beneath the membrane, I make a point of combing the mortar into a uniform pattern of parallel ridges. This is added insurance against bond failure, because the open ridges provide uniform support and prevent the formation of air pockets. All this takes a lot of cement -- plan on using about half again as much as you would use in a similar installation without the mat.

Counter tile and nosing. After troweling more thinset onto the exposed countertop edges, I'm ready to begin setting tile (Figure 4). Whenever possible, I like to start my layout with full tiles at the edges and ends of the counter, and that's the approach I took with this L-shaped kitchen (see "Layout Tips," below).

Figure 4.Full tiles are set from an outside corner of the layout toward the sink cutout. Installing a piece of nosing against one edge of the corner tile determines how much the remaining tiles should be held back from the edge to accommodate the remaining nosing (top). Nosing pieces are subject to hard knocks, so they're generously back-buttered to ensure that they're thoroughly embedded (bottom).

To install the nosing pieces, I first coat the substrate, then generously back-butter each piece with thinset to ensure complete embedment. I take extra care with this step, because poorly aligned nosing can make an otherwise well-done installation look sloppy. The best way to keep everything in line is to eyeball the trim lines as you do when selecting lumber for straightness. There's more than enough time to tweak the lines after initially bonding the tile, so there's no excuse for gross irregularities.

The nosing pieces also have to withstand more abuse than any other area of the countertop. If they're properly set to begin with, they'll never loosen, but there's a good chance that one or two edge pieces will be chipped by accidental impact somewhere down the line. I always order a few extra pieces for the job and tell my client to label them and store them in a safe place, so they'll be available when the original style or color has been discontinued.

Installing the backsplash. The tile backsplash in this kitchen matched the countertop (with the addition of an occasional decorative tile) and was aligned on the same grid. Unlike a countertop, a backsplash isn't subject to standing water, so the tiles can simply be adhered to the wall with mastic. For mounting tile on wallboard, I use Durabond D-2001 Multi-Purpose mastic, which is a water-based adhesive with good initial grab that provides a strong and permanent bond when dry.

In remodeling applications, though, the strength of the mastic bond will be limited by the strength of the bond between the wallboard and any existing wall covering. In this case, the backsplash area was covered with two layers of wallpaper. To ensure that it was bonded to the wallboard well enough to tile over, I coated the wall with mastic and let it "soak" for a half-hour (Figure 5).

Figure 5.To prepare the wallpapered wall for a tile backsplash -- which will be fastened directly to the wallboard -- the author first coats the area with a water-based mastic (top). Poorly bonded areas of wallpaper bubble away from the wallboard and are easily scraped off with a small trowel, leaving an acceptable tile base (center). The backsplash tiles are then attached to the wall with more mastic (bottom).

A few areas blistered up and I tore them away, exposing the wallboard beneath. Once those loose areas were removed, I attached the backsplash tiles to the exposed wallboard and remaining well-bonded wallpaper with more mastic, which I spread and combed with a 3/16-inch V-notch trowel.

Grouting and Sealing

I use a latex-modified grout in a color that complements the tile background. Dark colors are preferable because they're least likely to show dirt. Because smooth-struck joints are easier to keep clean, I strike the newly filled joints with a grout stick.

Nothing looks worse than sloppy corners and overflowing grout lines, so I also take the time to cut excess grout out of the corners -- where the wall meets the counter, for example, as well as along the top of any finished edge. A 2x5-inch rectangular margin trowel or putty knife works well for this.

After sponging the excess grout from the face of the tile, I let the tile dry for ten minutes or so until a surface haze develops. Rubbing the tile with a clean, dry rag removes the haze and brings the tile to a nice shine. The following day, I give the job a quick cleaning with a light tile cleaner. Glazed tile buffs up nicely.

Finally, I apply a high-quality grout impregnator-sealer. Don't cut corners here -- using the best sealer you can find is cheap insurance against problems and callbacks later. I've had good results with MiraSeal 511 Porous Plus (Laticrete, 800/243-4788, www.laticrete.com). I give every joint three coats, allowing at least four hours between coats. Although even this doesn't guarantee that the tile and grout will stay clean, it does protect the grout from staining. If the joints are struck smooth and then sealed well, the homeowner should be able to clean away nearly any kind of common dirt or grime. Because continued exposure to food acids and household cleaning products will eventually reduce the sealant's effectiveness, it's a good idea to reapply a coat of sealer every two years or so.

Tom Meehanand his wife, Lane, own Cape Cod Tileworks in Harwich, Mass.