Renovation 4th Edition

by Michael Litchfield

  Applying a mortar bed

  ting bed for wet and dry installations. It’s stable,

  takes strength and a

  unaffected by moisture, and easily cut and

  lot of skill. After

  attached. Backer board is also called cementi-

  installing a curing

  tious backer units (CBUs), HardieBacker®,

  membrane and

  Durock®, and WonderBoard—the last three being

  attaching wire mesh,

  you must carefully

  popular brands. These products feature a

  mix and trowel the

  cement-based core, reinforced by fiberglass mesh

  mortar on, level or

  or integral fibers. Because there’s considerable

  plumb float strips,

  variation among brands, always consult product

  and screed off excess

  literature for details on installation.

  mortar until the bed

  is uniformly flat.

  Glass-mat gypsum board. This board (one

  Then, after it has set

  brand is DensShield®) has a water-resistant core

  a bit, use a wood float

  and a heat-cured acrylic coating. It’s not as rug-

  to roughen its surface

  ged as backer board, but it’s an acceptable setting

  slightly, which

  bed in tub surrounds and other light-duty wet

  improves the

  areas. Don’t confuse this product with drywall.

  adhesion for the

  thinset to follow.

  Glass-mat gypsum board is specifically designed

  as 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 instal-

  lations. Moisture-resistant drywall is an accept-

  able substrate in damp or wet installations only

  when it is covered with a waterproofing mem-

  brane and then a mortar bed or backer board.

  Tile applied directly to drywall in wet installa-

  tions invariably fails sooner or later, often

  because people showering bump the walls, com-

  pressing the drywall’s 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.

  456 chapter 16

  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 11⁄8 in.

  thick (for example, 1⁄2-in. plywood underlayment

  laminated to a 5⁄8-in. plywood subfloor). On

  walls, 5⁄8-in. plywood is the minimum. Never use

  particleboard, OSB, or interior-grade plywood as

  setting beds.

  Self-leveling compounds. Self-leveling com-

  pounds (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

  Here, a tiler uses a margin trowel to apply thinset to a trimmed slate tile. With

  onto out-of-level floors. With a small amount of

  the correct consistency, thinset spreads easily yet will adhere to a trowel

  troweling, they spread across the floor and, with-

  turned on edge. Because polymer-modified thinsets have great bonding

  in minutes, start to set. Just two hours later,

  strength, you’re safer wearing rubber gloves. Also, be sure to clean tools

  you’ve got a hard, almost perfectly level mortar-

  immediately.

  setting bed ready to tile.

  That’s the short list of common setting beds.

  For other materials, see “Odd or Problematic

  priate for virtually all setting-bed materials.

  Setting Beds” on p. 465.

  Thinsets also are used to laminate rigid setting

  beds to substrates to create an inflexible sub-

  adheSiVeS

  structure for tiling. (Construction adhesive is

  also used in such laminations, but it is flexible,

  Once you’ve chosen a suitable setting bed for

  so it doesn’t achieve the rigidity of a thinset

  your wet or dry installation, choose a compatible lamination.)

  adhesive. Adhesives vary greatly from brand to

  Despite the cement ingredients they have in

  brand, so again, always follow the manufacturer’s common, thinsets vary widely, depending on

  mixing and application instructions exactly.

  their additives. Water-based thinsets are the weak-

  There are three major groups of adhesives: mas-

  est of the group, although they are generally

  tics, which come ready-mixed; thinset adhesives,

  stronger than mastics. Latex- and acrylic-based

  which are cementitious powders generally mixed thinsets (also known as polymer-modified thin-

  on site just before setting the tile; and epoxy thin-

  sets) are strong, somewhat water-resistant, and,

  sets that, like most epoxies, require you to mix a

  all in all, the best choice for bonding tile to backer

  hardener and a resin.

  board, mortar beds, SLCs, drywall, and concrete

  Organic mastics are the least expensive of the

  slabs. And they’re a close second for bonding

  three adhesive options. Because they come pre-

  almost everything else.

  mixed, they’re the most convenient option, but

  Most thinsets are mixed from powder. After

  they’re also the weakest. They are OK for attach-

  mixing, they have a “bucket life” of about two

  ing tiles to dry counters or walls—over drywall,

  hours. After being troweled onto a setting bed,

  for example—but they’re inappropriate where

  they start to set in 15 to 20 minutes.

  there’s water, heavy use, or heat. Mastics just

  epoxy thinsets have excellent compressive and

  don’t have the strength of thinsets.

  tensile strengths. They bond well and yet retain

  Mastics require a nearly flat setting bed. That

  flexibility when cured. After drying, they are

  is, when they are applied thickly to fill voids, they unaffected by moisture, so they’re suitable for all

  neither cure completely nor bond thoroughly.

  situations and substrates. There’s a catch, of

  Mastic cleans up well with water or solvent if you course: Epoxies are four or five times more

  remove the excess material at once. Opened con-

  expensive than other thinsets and quite tempera-

  tainers don’t keep well, so throw away any left-

  mental. You must mix the liquid resins and hard-

  over mastic after you’ve set the tiles.

  eners in exact proportions with the dry ingredi-

  Thinsets have great bonding and compressive

  ents. Setting times are similarly exacting. If

  strength. Being cement based, they bond best

  directions say 20 minutes, you can set your

  with mortar beds or backer board but are appro-

  watch by them. Above all, clean up epoxy before

&nbs
p; tiling

  457

  MeMbraneS

  Tile, grout, and many setting beds are unaffected

  zzzzzz Waterproofing a tub

  Surround

  by water. But they are porous, so water can

  Water-resistant

  migrate through them, potentially damaging ply-

  (WR) drywall

  wood substrates or wood framing. To prevent

  or greenboard

  damage in damp or wet areas, install a water-

  proofing membrane first. Even areas that are nor-

  1

  mally dry, such as entryways, should have a mod-

  /8-in.

  gap

  Waterproof

  est building-paper membrane if the floors will be

  membrane

  subject to wet mopping and dripping umbrellas.

  For walls above the water line in wet areas

  and for countertops subjected to occasional

  Fiberglass

  mesh tape

  water, a 15-lb. building-paper membrane is stan-

  dard, but installing a 60-minute stucco paper

  (which is impermeable for 60 minutes) makes

  Thinset

  sense. It’s stronger, less likely to tear, and more

  water-resistant. When installing such mem-

  branes, overlap the lower courses and vertical

  4-in.

  seams of paper by 4 in. Although some builders

  overlap

  recommend 4-mil polyethylene as a waterproof-

  ing membrane, stucco paper has one big advan-

  Backer

  tage: Unlike plastic, it is semipermeable.

  board

  Tile

  This tub surround would be sufficiently rigid

  without the WR drywal . But instal ers frequently

  add a drywal layer to build up the wal thickness

  when they’ll be using bullnose edge trim.

  it sets; some types sponge clean with water, oth-

  P R O T I P

  ers with solvents.

  Manufacturers frequently change

  grout

  their grout colors, so buy 10%

  more than you need for your cur-

  Grout is a specialized mortar that seals the joints

  rent installation. once the job is

  between tiles. Most grouts contain sand, cement,

  done, wrap the extra grout in a

  and a coloring agent. Grout may also contain

  plastic bag, label it as to where it

  additives to stabilize color, increase water and

  was used, and store it in a dry

  stain resistance, and increase strength and

  place. While you’re at it, buy

  flexibility. Most grouts and premixed additives

  caulking the same color as your

  are sold as a powder, which is subsequently

  grout; many tile stores carry

  mixed with liquid and allowed to stand (or slake)

  color-matched caulk, both

  for 10 minutes before final stirring to the correct

  sandless and sanded.

  consistency.

  Use sandless grout for joints narrower than

  1⁄8 in. Use sanded grout for joints 1⁄8 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.

  All wet installations need a waterproofing membrane.

  Here, a tub surround gets two layers of Fortifiber’s Super

  Jumbo Tex 60 Minute stucco paper, which is a fiber-

  reinforced barrier that’s tougher and more water-resistant

  than regular building paper.

  458 chapter 16

  Therefore, it allows water to escape should any

  When checking surfaces for plumb

  get behind the barrier.

  and level, take several readings with a

  Below the water line, such as in a shower pan,

  spirit level, especially in corners. If

  you need to protect wood substructure with an

  they’re out of plumb, tile joints won’t

  align, and the mismatch will be

  impervious membrane. Thus most shower pans

  glaringly obvious. Correct the

  are lined with sheet rubber, such as 30-mil, fiber-

  condition or don’t tile.

  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 gener-

  alizations. Follow the manufacturer’s installation

  instructions for specific adhesives, membranes,

  and setting-bed materials.

  Getting Ready to Tile

  If the substructure beneath the tile isn’t sturdy

  and stable, the job won’t last. Likewise, if walls

  aren’t plumb or floors aren’t level, tiles may

  adhere, but they may not look good. Start by

  assessing the existing surfaces. And that will

  inform your next steps, which can range from

  merely sanding finish surfaces to tearing out and

  zzzzzz corner out of Plumb

  reframing with studs and joists. The condition of

  existing floors, walls, and counters will also

  determine which setting bed you choose—and

  whether you should tile at all.

  aSSeSSing areaS to be tiled

  To check whether floors or countertops are level,

  use a long spirit level or a shorter level atop a

  perfectly straight board. Take several readings

  and use a pencil to mark individual high spots

  and dips. If variations from level exceed 1⁄8 in. in

  10 ft., floating a mortar bed or pouring SLC may

  be your best bet for establishing a flat setting

  bed. If the surface irregularities are less than that

  or the substrate just needs stiffening, adding a

  single layer of backer board may be all you need.

  If room corners aren’t square or facing walls

  aren’t parallel, you may need to angle-cut floor

  tiles around the room’s perimeter. This is not

  ideal, especially in narrow alcoves or hallways,

  but baseboard trim will partially cover those

  angled cuts. Similarly, at the back of counters,

  blacksplashes will cover angle-cut tiles.

  To check walls for plumb, use a long spirit

  level or a plumb bob; a taut string is also handy

  to detect high and low spots. Begin by surveying

  the entire wall. Unless the tiled corners are

  plumb, you’ll have tapering cuts or mismatched

  Corner wal s too far out of plumb can’t

  grout lines where the planes converge. To correct

  be tiled successfully. Their tile joints

  out-of-plumb walls, your choices are floating a

  won’t align, and the mismatch will be

  mortar bed, reframing the walls, or not tiling at

  glaringly obvious.

  tiling

  459

  Removing the toilet lets you reinstall it on top

  of the new tile. Some people mistakenly leave the

  toilet in place and as a result are forced to make

  a lot of unsightly tile cuts around its base, which

  can also be troublesome to caulk an
d maintain.

  Begin by turning off the shutoff valve to stop

  incoming water, disconnect the supply line, flush

  the toilet and remove the remaining water, and

  disconnect the anchor bolts holding the base to

  the floor.

  Because toilets are heavy, find someone to

  help you move the toilet out of the way. To block

  septic gases and keep objects from falling

  through the closet flange into the closet bend,

  stuff a plastic bag filled with crumpled newspa-

  per into the pipe (don’t forget to remove it before

  reinstalling the toilet).

  If you’re replacing tub/shower walls or installing backer board, protect chrome

  With the waste pipe temporarily sealed, take a

  gooseneck pipes or threaded spout stubs by replacing them with 6-in. pipe

  look at the toilet’s closet flange atop the closet

  nipples. The nipples are placeholders for the originals, ensuring that pipe stubs bend. Ideally, the top of the flange should be the line up to holes in the backer board. Here, Foilastic flashing reinforces the

  same height as the finish floor. If your tiling

  waterproofing membrane and later will serve as a dam for silicone caulking.

  increases the height of the floor 1⁄2 in. or less, the

  height of the flange shouldn’t be a problem. Just

  run tiles to within 1⁄8 in. of the flange. When you

  all. Note: A wall that’s plumb in the corner may

  apply a new wax ring to the bottom of the toilet

  have a twisted stud elsewhere that throws another horn, the wax will compress and seal the joint

  section out of plumb.

  Finally, survey surfaces for water damage,

  P R O T I P

  deflection, and other factors that could affect tile.

  Examine the bases of bathroom and kitchen fix-

  tures for discoloration, delamination, and spring-

  the thick and thin

  Weather-resistant barriers

  and flashing designed for exteri-

  iness, especially under toilets and tubs.

  Crumbling grout atop a tub often means that

  of Setting beds

  ors often double as waterproof

  membranes indoors, beneath

  water has gotten behind the tile. Open kitchen

  thin-bed installations such as latex thin-

  tile. after all, a shower is just

  and bath cabinets and examine the undersides of

  set adhesive over backer board are, well, thin.

  indoor rain. although sold pri-

  sinks and countertops. If you see discoloration,

  because they offer little depth for adjust-

  marily as stucco paper,

  probe it with an awl to determine whether mate-