Tile can be set on a variety of setting beds. Keep in mind that the substrate below the setting bed must be securely attached to the framing mem­bers. That assembly must be thick and stable enough to support loads with minimal deflection (J4(> of the span). And when used in damp or wet areas, it needs to remain unaffected by sustained exposure to water.

Mortar beds. Where walls aren’t plumb, floors aren’t flat, and corners aren’t square, mortar beds are usually the best setting bed. They can easily be screeded level or plumb to create a flat sur­face. In fact, a mortar bed is the only practical choice if you’re tiling the sloping floors of a shower stall. But few novices have enough skill to float a mortar bed. If your surfaces are badly out

of whack and you’re not experienced in floating mud, hire a pro for this job.

Backer board. If walls and floors are reasonably plumb and level, backer board is a durable set­ting bed for wet and dry installations. It’s stable, unaffected by moisture, and easily cut and attached. Backer board is also called cementi­tious backer units (CBUs), HardiBacker®, Durock®, and WonderBoard—the last three being popular brands. These products feature a cement-based core, reinforced by fiberglass mesh or integral fibers. Because there’s considerable variation among brands, always consult product literature for details on installation.

Glass-mat gypsum board. This board (one brand is DensShield®) has a water-resistant core and heat-cured acrylic coating. It’s not as rugged as backer board, but it’s an acceptable setting bed in tub surrounds and other light-duty wet areas. Don’t confuse this product with drywall. Glass – mat gypsum board is specifically designed to be a tile backer.

Unpainted drywall. Drywall is an acceptable setting bed where walls stay dry. Caution: Never bond tile directly to drywall in damp or wet installations. Water-resistant (WR) drywall (or greenboard) is an acceptable substrate in damp or wet installations only when it is covered with a waterproofing membrane and then a mortar bed or backer board.

Tile applied directly to drywall in wet installa­tions invariably fails sooner or later, often because people showering bump the walls, com­pressing the drywalls gypsum core. No longer supported evenly by the core, the grout loosens, water enters and soaks the paper, and—all too often—the framing rots.

Exterior-grade plywood. It’s usually a mistake to use plywood, even exterior grade, as a setting bed. Exposed to moisture, plywood tends to swell and delaminate. If you must use it as a setting bed for floor or countertop installations, be sure to cover it with a continuous waterproofing membrane; the base should be at least 1 Ys-in. thick (for example, h-in. plywood underlayment laminated to a %-in. plywood subfloor). On walls, %-in. plywood is the minimum. Never use parti­cleboard, oriented strand board (OSB), or interi­or-grade plywood as setting beds.

Self-leveling compounds. Self-leveling com­pounds (SLCs), such as LevelQuik®, have many of the virtues of a mortar bed but require few of the skills needed to float one. Basically, SLCs are fortified mortar powders mixed thin and poured onto out-of-level floors. With a small amount of troweling, they spread across the floor and, with­in minutes, start to set. Just 2 hours later you’ve got a hard, almost perfectly level mortar-setting bed ready to tile.

That’s the short list of common setting beds. For other materials see "Odd or Problematic Setting Beds,” on p. 392.

ADHESIVES

Once you’ve chosen a suitable setting bed for your wet or dry installation, choose a compatible adhesive. Adhesives vary greatly from brand to brand, so again, always follow the manufacturer’s mixing and application instructions exactly.

There are three major groups of adhesives: mas­tics, which come ready mixed; thinset adhesives, which are cementitious powders generally mixed on-site just before setting the tile; and epoxy thin – sets that, like most epoxies, require your mixing a hardener and a resin.

Organic mastics are the least expensive of the three adhesive options. Because they come premixed, they’re the most convenient option, but they’re also the weakest. They are okay for attaching tiles to dry counters or walls—over dry- wall, for example—but they’re inappropriate

where there’s water, heavy use, or heat. Mastics just don’t have the strength of thinsets.

Mastics require a nearly flat setting bed. That is, when they are applied thickly to fill voids, they neither cure completely nor bond thoroughly. Mastic cleans up well with water or solvent if you remove the excess material at once. Opened con­tainers don’t keep well, so throw away any left­over mastic after you’ve set the tiles.

Thinsets have great bonding and compressive strength. Being cement based, they bond best with mortar beds or backer board but are appropriate for virtually all setting-bed materials. Thinsets are also used to laminate rigid setting beds to sub­strates in order to create an inflexible substructure for tiling. (Construction adhesive is also used in such laminations, but it is flexible and so doesn’t achieve the rigidity of a thinset lamination.)

Despite the cement ingredients they have in common, thinsets vary widely, depending on their additives. Water-based thinsets are the weakest of the group, although they are generally stronger than mastics. Latex – and acrylic-based thinsets (also known as polymer-modified thin – sets) are strong and somewhat water resistant and are, all in all, the best choice for bonding tile to backer board, mortar beds, SLCs, drywall, and concrete slabs. And they’re a close second for bonding almost everything else.

Most thinsets are mixed from powder. After mixing, they have a "bucket life” of about 2 hours. After being troweled onto a setting bed, they start to set in 15 minutes to 20 minutes.

Epoxy thinsets have excellent compressive and tensile strengths. They also bond well and yet retain flexibility when cured. After drying, they are unaffected by moisture and so are suitable for all situations and substrates. There’s a catch, of course: Epoxies are four or five times more expensive than other thinsets and quite tempera­mental. You must mix the liquid resins and hardeners in exact proportions with the dry ingredients. Setting times are similarly exacting. If directions say 20 minutes, you can set your watch by them. Above all, clean up epoxy before it sets; some types sponge clean with water, others with solvents.

GROUT

Grout is a specialized mortar that seals the joints between tiles. Most grouts contain sand, cement, and a coloring agent. Grout may also contain additives to stabilize color, increase water and stain resistance and increase strength and flexi­bility. Most grouts and premixed additives are sold as a powder, which is subsequently mixed with liquid and allowed to stand (or slake) for

Waterproofing a Tub Surround

This tub surround would be sufficiently rigid without the WR drywall. But installers frequently add a drywall layer to build up the wall thickness when they’ll be using bullnose edge trim.

10 minutes before final stirring to the correct consistency.

Use sandless grout for joints narrower than ‘/ in. Use sanded grout for joints Z in. and wider.

Most tile suppliers carry grout in hundreds of colors. Whatever the color, remember that the greater the contrast between grout and tile, the more obvious the joints and workmanship.

MEMBRANES

Tile, grout, and many setting beds are unaffected by water. But they are porous, so water can migrate through them, potentially damaging plywood sub­strates or wood framing. To prevent such damage in damp or wet areas, install a waterproofing membrane first. Even areas that are normally dry, such as entryways, should have a modest building – paper membrane if the floors will be subject to wet mopping and dripping umbrellas.

For walls above the water line in wet areas and for countertops subjected to occasional water, a 15-lb. building-paper membrane is stan­dard, but installing a 60-minute stucco paper
(which is impermeable for 60 minutes) makes sense. It’s stronger, less likely to tear, and more water resistant. When installing such membranes, overlap the lower courses and vertical seams of paper by 4 in. Although some builders recom­mend 4-mil. polyethylene as a waterproofing membrane, stucco paper has one big advantage: Unlike plastic, it is semipermeable. Therefore, it allows water to escape should any get behind the barrier.

Below the water line, such as in a shower pan, you need to protect wood substructure with an impervious membrane. Thus most shower pans are lined with sheet rubber, such as 30-mil, fiber-reinforced chlorinated polyethylene (CPE), whose seams are overlapped and chemically bonded with a solvent. Of course, you don’t want to puncture CPE shower-pan membranes with screws or nails. Instead, roll the membrane onto a fresh layer of latex thinset adhesive, and cover it with a mortar bed.

Note: The comments in this section are gener­alizations. Follow the manufacturer’s installation instructions for specific adhesives, membranes, and setting-bed materials.

Setting means positioning and adhering tile to a substrate. Grouting means sealing the joints between tiles with a special mortar.

A notched trowel spreads adhesive. Two edges of the tool are flat, designed to spread the adhe­sive initially. Then on subsequent passes, use the notched edges to comb a series of parallel ridges, which will spread evenly when the tile is pressed into it. Notch height should be about two-thirds the thickness of the tile.

A margin trowel is a utility tool that’s great for mixing small batches of powdered adhesives, cleaning mortar off other trowels, buttering indi­vidual tiles with adhesive, and removing excess grout or adhesive that oozes up between tiles.

Plastic spacers and wedges enable you to shim individual tiles so their edges align to your layout lines.

A beater board is just a flat board placed over tile sections and rapped gently with a rubber mallet to seat the tiles in the adhesive. Not all tilesetters use a beater board. Many just press tiles in firmly or use a fist to seat them better.

A grout float (rubber-faced trowel) applies grout in a process that takes at least two passes. Holding the face of the grout float at about 30°, sweep the grout generously over the tile and pack it into the joints. Then, holding the float almost perpendicular to the surface, remove the excess grout, unloading it periodically into a bucket. To avoid pulling grout out of the joints, make your passes diagonally across the tile joints.

Round-cornered, tight-pored sponges are less likely to pull grout out of tile joints. After grout starts to haze over, wipe lightly with a dampened sponge, rinsing the sponge often. Get several types of sponges. Kitchen sponges with scrub pads on the back are useful for removing stub­born grout.

A mixing bit in an electric drill can mix large amounts of powdered adhesives or grout. Slow mixing speeds of 300 rpm to 400 rpm work best. And keep the bit immersed to minimize mixing in air, which weakens the batch. Wear a respira­tor mask.

Materials

Here’s a quick survey of materials you might use to create a durable tiling job.

Think of the job as if it were a layer cake. For example, in floor tiling, the bottom layer (concep­tually the table under the cake) would be the floor joists. Nailed to the joists, in most cases, is a plywood substrate. For a wet installation such as a shower wall, next comes a waterproofing mem­brane, followed by a setting bed of cementitious backer board or a mortarbed. Troweled onto the setting bed is a setting material, typically thinset adhesive or organic mastic. Tiles are applied to the setting bed, and once the bed has hardened, tiles joints are grouted. Later, a sealer may be

Mastering the mess

Controlling the mess is a big part of successful tile setting. If you’re tiling a tub surround, cover floors with builder’s paper or plastic, mask off cabinets, and line the bathtub with a heavy can­vas drop cloth before you start. Masonry debris is very abrasive, so vacuum as it accumulates. Also, keep a clean 5-gal. plastic bucket (joint compound pails are perfect) full of clean water for sponging mortar, adhesive, or grout off tools. Last, a bundle of clean dry rags is useful for buffing dried grout haze off tile and soaking up messes.

I Typical Wet Installation Floor applied to make tile and grout more water or stain resistant.

Methods and materials are rarely predictable in renovation, so it’s a good idea to survey the back or underside of the surface you’re about to tile, both to see how many layers there are and to check if they’re in good condition. You can pull out a heating register to see a cross-section of the flooring, for example. Or test-drill a small hole in an inconspicuous spot to determine the thickness and composition of an existing wall, floor, or countertop.

There are almost as many physical distinctions among tiles as there are tile types, but the most important traits to consider are water resistance and durability.

Water resistance. Here, three of four official categories of tiles include the word vitreous, which means glasslike, and suggest how much the tile will resist or absorb water. The categories are nonvitreous, semivitreous, vitreous, and impervious. Nonvitreous is the most absorptive, and impervious the most water resistant.

Use nonvitreous tiles on dry areas, such as interior fireplace surrounds and hearths. Use semivitreous or better on shower walls, tub sur­rounds, backsplashes, and areas that are inter­mittently wet. Use vitreous and impervious tiles for wet installations like pools, hot tubs, and outdoor surfaces in rainy cli­mates. In general, the less water a tile absorbs, the less hos­pitable it will be to bacteria and mold. That’s why hospitals and laboratories usually use imper­vious tiles.

Durability. Tile durability rat­ings, based on structural strength and surface imperfec­tions, typically assign softer, weaker tile to less demanding areas and harder, impervious tile to heavily trafficked, wet, and outdoor areas. In like man­ner, tiles are rated for walls, floors, and counters. A reputable

tile supplier will give you good advice on appro­priate uses and durability and will stand behind the tiles you buy.

Tools

Many tile suppliers sell or rent tiling tools and offer workshops on techniques and tool use.

Tools and safety. Tiling is deliberate, methodical work and is not as inherently dangerous as some remodeling tasks. Still, it poses hazards; so for starters, please note these minimal safety rules:

► o Use a voltage tester to ensure that power has been shut off to outlets, fixtures, switches, and devices you’ll work near. In addition, ensure that bathroom and kitchen receptacles have ground-fault circuit interrupter (GFCI) protection, as spelled out in Chapter 11. Corded power tools should be double insulated and grounded with a three – prong plug. Or use cordless tools instead.

► Rubber gloves reduce the risk of electrical shock and prevent skin poisoning from prolonged handling of mortar, adhesives, sealers, and the like.

► Wear goggles when cutting tiles, whether making full cuts with a wet saw or nibbling bites with a tile nipper. Tile shards can be as sharp as a scalpel.

► Wear a respirator mask when mixing masonry materials, applying adhesive, cutting cementitious backer board, and so on.

► Knee pads will spare you a lot of discomfort. Buy a pair that’s comfortable and flexible enough to wear all day. Flimsy rubber knee pads won’t protect your knees.

► Open windows and turn off pilot lights on gas appliances when using volatile adhesives or admixtures. Closely follow manufacturer’s instructions.

BASIC TOOLKIT FOR TILE

► Safety equipment: rubber gloves, goggles, respirator mask, voltage tester, and knee pads.

► Measuring and layout: straightedges, framing square, spirit level, pencil or felt – tipped pen, chalkline, tape measure, story pole, and scribe (or an inexpensive student’s compass).

► Setting and grouting: notched trowel, margin trowel, plastic spacers and wedges, beater board, rubber mallet, grout float, round-cornered sponge, and clean rags.

► Cutting: snap cutter, tile nippers, utility knife with extra blades, and wet saw.

► Cleanup: sponges, rags, plastic buckets, plastic tarps, and shop vacuum.

► Miscellaney: hammer and wire cutters.

MEASURING AND LAYOUT

Substrates are never absolutely flat or perfectly plumb, so layout is a series of reasonable approx­imations. Clean tools give the most accurate readings, so wipe off mortar or stray adhesive before it dries.

► A 4-ft. spirit level is long enough to give you an accurate reading. It’s indispensable for checking plumb and leveling courses of wall tiles. If a 4-ft. level proves unwieldy on the short end walls of a bathtub, use a 2-ft. level or a torpedo level instead.

► A tape measure lets you measure areas to be tiled, triangulate diagonals for square, and perform general layout.

► Snap a chalkline to mark tile layout lines before applying adhesive.

► Straightedges are useful for aligning tile courses, marking layout lines on substrate, and guiding cuts on backer board and plywood. Professional tilesetters have metal straightedges of different lengths, but wood’s okay if it’s straight and sealed to resist water.

► A framing square establishes perpendicular layout lines on floors, walls, and countertops.

► A story pole is a long straight board marked in increments representing the average width of a tile plus one grout joint (see "Storytelling," on p. 395). With it, you can quickly see how many tiles will fit in a given area, as well as where partial tiles will occur.

► Use a scribe to fit sheet materials (cementitious backer board, plywood) to a bowed wall or to transfer the arc of a toilet flange to a tile.

CUTTING

Always wear goggles when cutting or nipping tile, especially when using power tools.

A snap cutter works well on manufactured vitreous and impervious tile. This tool has a little cutting wheel—make sure it’s not wobbly or

Snap cutters work great for straight cuts on vitreous tile. With this model, you score the tile in one pull and then push down on the tool’s wings to snap the tile along the scored line. Here, blue painter’s tape keeps the cutter’s wings from scratching the tiles.

chipped—that should score the tile in one pull. Then reposition the handle so the "wings” of the tool rest on the scored tile, and press sharply to snap it. Note: When using a snap cutter, it’s tough to get a clean break on nonvitreous tile, tiles with textured surfaces, and floor tiles. For those you’ll need to rent a wet saw.

A wet saw, which you can rent, is especially use­ful when cutting nonvitreous or irregular tiles or trimming less than 1 in. off any tile. It cleanly cuts all tile types. To make U-shaped cuts around soap dishes and the like, make a series of parallel cuts with the wet saw before removing the waste with tile nippers.

Tile nippers allow you to cut out sections where tiles encounter faucet stems, toilet flanges, and the like. Nippers require some practice and lots of patience. Take small nibbles—use only part of the jaws—nibbling away from the sides of a cut into the center, gradually refining the cutout.

As you approach your final cut-lines, go slowly.

A carbide-tipped hole saw is perfect for cutting holes for faucet stems and pipe stubs. To be safe around pipes and water, use a cordless drill with this saw.

A handheld grinder with a diamond blade can cut curved lines in tile (make a series of shallow passes) or plunge cuts for holes in the middle of a tile. Be sure to stop the cuts short of your cut-lines and remove the waste with a pair of
nippers. Because a grinder is noisy and throws lots of dust, use it only outdoors, and wear a respirator mask and eye protection.

A utility knife scores cementitious backer board (which you snap like drywall), marks off tile joints in fresh mortar, cleans stray adhesive out of joints, and so on. However, if you’ve got much backer board to cut, instead use a handheld grinder with a diamond blade.

Keep tile from overheating and cracking as you drill by immers­ing it in a water-filled box just larger than the tile—build the box from scrap wood and caulk it so it won’t leak. If countertop tile is already installed, build a dam of plumber’s putty around it and add water before drilling. Mexican and other handmade tiles tend to crack when drilled without mortar support under­neath, so install them before drilling. To avoid electrical shocks, use a cordless drill.

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