Tile glossary

Ceramic tile

A clay-bodied tile fired at a relatively low temperature (around 1,800–2,000°F), typically with a glazed face over a softer reddish or white biscuit body.

Ceramic is the cheapest tile category and easy to cut with a $50 score-and-snap — fine for walls and light-traffic dry floors, but its 0.5–3% water absorption rate disqualifies it from any wet-area floor or exterior install. Most 3×6 subway tile is ceramic; the same shape in porcelain costs roughly 1.5× as much for a reason.

See also: cost calculator

Porcelain tile

A denser, harder tile fired at higher temperatures (2,200°F+) from a finer clay mix, with an ANSI A137.1 water absorption rate of 0.5% or lower.

The default for any floor, wet area, or exterior install. Porcelain costs 30–60% more than ceramic and demands a wet saw for clean cuts (score-and-snap chips the edge), but it earns it in durability — most porcelain is PEI 4 or 5 and tolerates freeze-thaw cycles ceramic doesn't.

See also: cost calculator

Natural stone

Quarried stone cut into tile format — marble, travertine, limestone, slate, granite, and onyx are the common species.

Sold by the slab or the tile, every piece is unique and dye-lot variation is the norm rather than the exception. All porous stone (marble, travertine, limestone) needs a penetrating sealer before grouting and annually after — skip that and the grout slurry permanently stains the face. Polished marble is one of the lowest-DCOF surfaces on the market and is genuinely dangerous on a wet floor.

Glass tile

Tile made from recycled or virgin glass, typically sold as mosaics on mesh sheets for backsplashes and accent strips.

Cuts require a glass-specific wet saw blade ($40–60) — a standard porcelain blade chips and clouds the edge. Most glass tile is wall-rated only because the surface is too slick for floor DCOF requirements, and the setting bed shows through translucent glass, so you back-butter with bright white thinset rather than the standard gray.

Mosaic

Any tile 2 inches or smaller on its largest edge, usually pre-mounted on a 12×12 mesh or paper sheet for sheet-by-sheet install.

Sold by the sheet but installed by the tile — labor is priced on the underlying piece count, not the sheet count, so a $4–8/sq ft labor premium over standard 12×12 is typical. The grout-grid density makes mosaic the default for shower floors, where the joint pattern pushes wet DCOF well above the 0.42 minimum.

Terracotta tile

Unglazed earthenware tile fired at low temperature, in the warm red-orange color of the natural clay. Saltillo is the Mexican handmade variety, cotto is the Italian.

Highly porous (5–15% water absorption) and demands a penetrating sealer before grout and annually thereafter — without it, the clay drinks water and grout slurry permanently. Hand-finished Saltillo has irregular edges and is set with a wide 1/4–3/8 in joint to embrace the variation; rectified terracotta sets with a 1/8 in joint like any other tile.

Vitrified tile

A ceramic tile fired hot enough that the body fully vitrifies (turns glassy) — functionally equivalent to porcelain, with the same ≤0.5% water absorption.

The term is more common in South Asian and European markets; in U.S. retail you'll see the same product labeled porcelain. If the spec sheet says ≤0.5% absorption per ASTM C373, it's vitrified regardless of the marketing word.

PEI rating

The Porcelain Enamel Institute's 1-5 abrasion-resistance scale for glazed tile, measuring how the glaze holds up under foot traffic.

PEI 1–2 is wall-only; PEI 3 handles residential light-traffic floors; PEI 4 is the default for kitchens, baths, and hallways; PEI 5 is for commercial entryways and restaurants. The rating only describes the glaze — an unglazed porcelain has no PEI and you read the abrasion spec off ANSI A137.1 directly.

Large-format tile

Any tile with at least one edge of 15 inches or longer, per ANSI A108.02 §4.3.7 and the TCNA Handbook.

The 15-inch threshold is the trigger for a substrate flat to 1/8 in over 10 ft, mandatory back-buttering, 95% mortar coverage, and lippage clips on every long edge. Running bond is also discouraged above 15 inches because of seam-midpoint lippage — a 1/3 offset or stacked layout is safer. Skip these requirements and the install fails within 2–3 years.

See also: tile size guide

Plank tile

A rectangular tile with a long aspect ratio (commonly 6×24, 6×36, 8×48, or 9×60), typically wood-look or stone-look porcelain.

Plank's whole visual purpose is to read as wood floor or a long-format stone, which means a 1/16 in joint with a matched grout is the right setup — contrast grout collapses the illusion. TCNA discourages running bond past a 1/3 offset because plank tile has the most kiln bow per linear inch of any tile shape.

See also: templates

Mosaic-on-mesh

A 12×12 (or 12×24) sheet of small tiles pre-mounted on a fiberglass mesh backing for sheet-at-a-time install.

The mesh sits between the thinset and the tile and reduces bond strength — okay for walls and dry residential floors, but TCNA does not allow mesh-mounted mosaic for submerged installs (pools, fountains). For those, look for face-mounted paper sheets that are peeled off after the thinset cures.

Gauged porcelain panel (GPP)

A thin (3–6 mm) large-format porcelain slab, sized up to 5×10 ft, covered by ANSI A137.3 and TCNA installation method W466.

Different beast from standard tile — the panels require two-person handling rigs ($300–600), a specific medium-bed mortar (Mapei Ultralite S2, Laticrete 4-XLT), and most installs are subcontracted to crews trained on the manufacturer's system. Don't accept a GPP install from a tile setter who doesn't show you their certification card.

Subway tile

A 3×6 rectangular wall tile, named after the white ceramic tile lining New York's subway stations from 1904 onward.

The single most-installed tile shape in the U.S. — cheap ($1–3/sq ft material), every brand makes it, every contractor can set it. Half-offset running bond is the default; 1/3 offset reads more contemporary; vertical stacked subway reads modern. Larger 4×12 or 4×16 'subway' is technically a different SKU but installs the same way.

See also: kitchen backsplash template

Penny round

Small round porcelain or ceramic tiles roughly the diameter of a U.S. penny (~3/4 in), sold pre-mounted on mesh sheets.

Common on shower floors, where the dense grout grid gives excellent slip resistance and the small tiles conform to the slope toward the drain. Expect a labor premium of $4–8/sq ft over standard mosaic because every penny needs the grout joint hand-tooled, and the joints are intentionally wide enough to read as part of the pattern.

Running bond

A pattern where each row is offset from the next, classically by half a tile (50%) — the same pattern as traditional brick coursing.

The default subway-tile layout. TCNA discourages 50% offset on any tile with an edge over 15 inches because kiln bow concentrates lippage at the seam midpoint — switch to 1/3 offset (33%) or a stacked layout for large-format. A 1/3 offset is also a quieter, more contemporary read on plank tile.

See also: running bond pattern

Herringbone

A pattern of rectangular tiles set at 90° to each other, forming a zigzag of V-shapes — typically rotated 45° from the wall axis for the classic look.

The labor premium is real — expect $3–6/sq ft over a straight-set tile of the same size because of the diagonal cuts at every perimeter edge. Waste is 15–20% rather than the standard 10%. The pattern requires a 2:1 aspect ratio (3×6, 4×8, 6×12) to lock together cleanly.

See also: herringbone pattern

Chevron

A pattern of parallelogram tiles (rectangular tiles with 45°-cut short edges) forming continuous V-seams at every row boundary.

Often confused with herringbone — chevron tiles are pre-cut at the factory to mate at the seam, herringbone is rectangular tiles butted at 90°. Chevron costs roughly 2× the per-square-foot price of an equivalent rectangular tile and the install is unforgiving; any out-of-square row instantly shows.

See also: chevron pattern

Versailles parquet

A historical French stone pattern using four different rectangle and square sizes derived from a single primary tile, interlocking into a 2×2 module that tiles across the floor.

Originally cut from limestone for the Galerie des Glaces; the modern porcelain version comes pre-cut as a kit with all four sizes proportioned to drop in. Labor is high ($8–15/sq ft over straight-set), and waste runs 18–25% — but the look is unmistakable and the pattern doesn't repeat visually at residential scale.

See also: Versailles pattern

Field tile

The primary tile that fills the open surface area of a wall or floor, as opposed to trim, accent, or border pieces.

When you order, the field tile is usually 85–95% of the order quantity. Specify dye lot when ordering and add a 5–10% overage in the same lot — getting a matching field-tile dye lot a year later for a repair is often impossible, and the new lot will read visibly different.

Bullnose

A tile with one or more rounded edges, used to finish an exposed tile edge (countertop nosings, shower-niche openings, wainscot tops).

Sold separately from the field tile at 3–5× the per-piece price; specify it at order time because matching a bullnose to a 2-year-old discontinued field tile is the hardest part of any tile repair. Single bullnose (one round edge) is standard; double bullnose (two adjacent rounds) is for outside corners.

Quarter round

A small (typically 1/2×6 or 3/4×6) tile trim piece with a quarter-circle cross-section, used to finish an inside corner between tile and tile or tile and another material.

The traditional cove-to-floor transition in tiled bathrooms; today most installers prefer a Schluter Dilex-EKE or similar metal profile because cementitious quarter round cracks at the flex point between substrates within a few years.

V-cap

A countertop edge trim with an L-shaped cross-section that wraps the front edge and short return underneath, finishing a tiled countertop nosing.

Mostly seen on older Southwestern and Mediterranean tiled-countertop installs; modern tile-countertop work either uses a Schluter Rondec/Jolly profile or accepts a square exposed edge. V-cap is still made by some Southwestern lines (Daltile, Talavera) and is the right call when you want the period look.

Pencil liner

A thin (typically 1/2×6 or 5/8×6) trim tile with a rounded, raised profile, used as a decorative horizontal band or to cap a wainscot.

Pure decoration — runs $4–10 per linear foot in ceramic, more in metal or stone. Often used as a chair-rail line in tiled wainscot or as a frame around a shower niche. Pair with a matching cove or quarter round for the inside corners to keep the period look consistent.

Listello

A decorative narrow band of tile (typically 2–4 inches tall, in mosaic, glass, or metal), set as a horizontal stripe through a field of plain wall tile.

Most popular in 1990s–2000s tile work; current taste leans away from listellos in favor of a fully clean tile field. If you're renovating and keeping the listello, source a matching piece before demo — discontinued listello SKUs are the single hardest tile component to match.

Cove base

A trim tile with a concave curve along the bottom edge, used to make a seamless tile-to-floor transition at the base of a wall.

The traditional commercial floor detail (school bathrooms, hospital corridors) because the curve eliminates the dirt-collecting 90° corner. Residential tile setters today usually substitute a Schluter Dilex-EKE or run the wall tile straight to a base shoe — true cove base is still available from American Olean, Daltile, and Crossville on commercial lines.

Schluter profile (Jolly / Rondec / Reno-U)

A family of aluminum, brass, or stainless metal edge trims from Schluter-Systems, designed to finish a tile edge cleanly without a bullnose.

Jolly is the right-angle L-profile (the workhorse); Rondec has a rounded face; Reno-U bridges two different floor heights. Costs $8–15 per 8 ft length, comes in dozens of finishes (brushed nickel, brass, matte black), and has displaced ceramic bullnose on most modern installs because it doesn't need a dye-lot match and is faster to set.

See also: tile size guide

Thinset

A cement-based adhesive mortar (also called dry-set or LHT mortar) used to bond tile to the substrate, mixed from powder with water or a polymer additive.

Categorized by ANSI A118: A118.1 is unmodified, A118.4 is modified (latex/polymer added for flex), A118.15 is the medium-bed mortar required for any tile 15 inches or larger. Get the wrong category and the install fails — A118.1 under large-format tile is a common DIY mistake.

Back-buttering

The technique of applying a thin layer of thinset directly to the back of each tile in addition to troweling the substrate, ensuring full mortar coverage.

Required by ANSI A108.5 on any tile 15 inches or larger and on any wet-area floor. The point is to fill the back-of-tile waffle pattern so the mortar contacts the full tile back — skip it on large-format and you'll have 50–60% coverage instead of the required 80–95%, with hollow spots and cracked tile within two years.

Lippage

The height difference between two adjacent tile edges after setting, measured perpendicular to the surface.

The trade-acceptable maximum is roughly 1/32 in for joints under 1/4 in, per the TCNA Handbook — visible enough to feel underfoot, small enough that a good installer hits it routinely. Large-format tile (≥15 in) is where lippage gets expensive: substrate flatness needs to be 1/8 in over 10 ft, and every long edge needs lippage clips (T-Lock, Spin Doctor) during set.

See also: tile size guide

Screed

A long straightedge (typically a 4–8 ft level or aluminum bar) drawn across wet mortar or floor leveler to strike it flat to a reference height.

Also used as a verb — 'screed the floor flat' before tiling. The reference is usually a pair of wood screeds or rebar pinned at the target height; you pull the screed across them to remove the high spots. A floor that's been screeded flat to 1/8 in over 10 ft is ready for large-format; out-of-spec floors need self-leveling underlayment.

Dry-fit

Laying out the field tile on the substrate without mortar to plan cuts, check the pattern's centerline, and confirm the perimeter cut sizes before committing to thinset.

The 20-minute step that prevents the all-too-common 'sliver cut on the focal wall' mistake — always dry-fit a row across the longest dimension, snap a centerline, and confirm both edges land on at least a half-tile cut. If one edge falls under a quarter-tile, shift the layout origin a half-tile to balance the cuts.

Layout line / chalk line

A reference line snapped on the substrate with a chalk-loaded string, used to keep tile rows true to a perpendicular grid.

The first physical step on any tile install — snap two perpendicular lines through the room's centerline, verify they're square with a 3-4-5 triangle, then set the first tile at the intersection and work outward. Skip this and the install runs out of true within four rows, which is invisible until the perimeter cuts show wildly different widths on opposite walls.

Cement board (HardieBacker / Durock)

A Portland cement-and-fiber sheet substrate (1/4 in or 1/2 in thick), screwed over a structural floor or wall to receive thinset and tile.

HardieBacker (James Hardie) is fiber-cement and lighter; Durock (USG) is cement with fiberglass mesh and slightly more rigid. Both are non-negotiable on tiled wet walls — drywall behind shower tile fails within five years. Set with 1-1/4 in cement-board screws, taped seams with alkali-resistant mesh, and a thinset bed under the panel on floors.

Backerboard

A generic term for any cementitious or coated-glass sheet substrate used under tile — covers cement board, glass-mat gypsum (DensShield), and lightweight coated foam (Wedi, Kerdi-Board).

Use the right one for the job — cement board for floors and full wet areas, DensShield for dry walls only, foam-core boards (Wedi, Kerdi-Board) for shower-pan curbs and benches where weight matters. DensShield in a shower is a warranty problem with most thinset manufacturers.

Self-leveling underlayment (SLU)

A cement-based pourable compound (LevelQuik, Henry 555, Mapei Novoplan, Ardex K15) that flows out flat under gravity to correct an out-of-flat subfloor.

Non-optional under large-format tile on any wood subfloor or any out-of-spec slab — the cost is $1.50–3.50/sq ft installed, but the alternative is cracked grout within a year. Use the right primer (manufacturer-specific) and a perimeter expansion strip; SLU bonded to a flexing wall edge cracks at the perimeter.

Uncoupling membrane (Schluter Ditra)

A polyethylene sheet with a waffled top surface and a fleece bottom, set in thinset between substrate and tile to isolate the tile layer from substrate movement.

Ditra (Schluter), Strata Mat (Laticrete), and Permat (Mapei) are the major brands. The fleece bonds to thinset above and below; the waffle gives a mechanical key for the upper thinset bed. Required by Schluter's warranty for any tile over a wood subfloor and useful (though not required) on a slab with a history of hairline cracking.

Waterproofing membrane (RedGard / Kerdi)

A liquid roll-on (RedGard, HydroBan) or sheet-applied (Schluter Kerdi, Wedi) membrane that creates a continuous waterproof layer between substrate and tile in showers and steam rooms.

ANSI A118.10 is the spec to look for. Roll-on goes down in two coats, second perpendicular to the first, at the manufacturer's wet-mil thickness — under-applied RedGard fails water-test inspection. Kerdi is overlapped and thinset-bonded at every seam. Either way, the membrane is the actual waterproof layer in a tiled shower; the tile and grout are not.

Anti-fracture membrane

A flexible membrane (sheet or liquid) installed under tile to absorb minor substrate movement and prevent cracks in the substrate from telegraphing up through the tile.

Different role from waterproofing, though some products (RedGard, HydroBan) do both. Required under tile on any slab with a known active crack; recommended over any wood subfloor with deflection at the upper end of the L/360 spec. Schluter Ditra is the most common, but Noble CIS Membrane and Laticrete Blue 92 are direct competitors.

Modified thinset

A thinset mortar that includes a polymer additive (latex, EVA, or acrylic) for improved flex and bond, meeting ANSI A118.4 or A118.11.

The right choice for almost every install over a wood subfloor, over Ditra, or in a wet area — the polymer absorbs the small flex movement that would otherwise crack an unmodified A118.1 bed. Exception: Schluter requires unmodified A118.1 over the top of Ditra (the modified version doesn't cure correctly sealed under tile), but modified under Ditra against the substrate.

Large-format mortar

A medium-bed mortar specifically formulated to be non-sagging at 1/2 in or thicker, meeting ANSI A118.15. Sometimes called LHT (large-and-heavy tile).

Required under any tile 15 inches or larger by ANSI A108.02 — standard thinset slumps under the weight and you get lippage and hollow spots. Mapei Ultraflex LFT, Laticrete 4-XLT, and Custom MegaLite are the main products in the category, all $40–60 per 50 lb bag (2× standard thinset).

Cementitious grout

Portland-cement-based grout (Custom Polyblend, Mapei Keracolor U, Laticrete PermaColor) mixed from powder, the cheapest of the three major grout categories.

$15–25 per 25 lb bag — but needs to be sealed 1–2 times per year with a penetrating sealer (Aqua Mix Sealer's Choice Gold, TileLab SurfaceGard) to resist staining, and the color fades over 5–10 years with UV and repeated sealing. Spot repairs in 5+ year cementitious grout almost always read different from the original.

See also: grout color guide

Urethane grout

A premixed single-component urethane grout (Mapei Ultracolor Plus FA, Bostik Hydroment Urethane), factory-sealed and stain-resistant out of the bucket.

Roughly 2× the cost of cementitious ($50–80 per quart) but no maintenance — never needs sealing and the color is stable for the life of the install. The sweet spot for kitchen and bath floors where cementitious would mean annual sealing trips and a fade visible at year five.

See also: grout color guide

Epoxy grout

A two-component epoxy resin grout (Laticrete SpectraLock Pro Premium, Mapei Kerapoxy, Custom CEG-Lite) meeting ANSI A118.3.

The hardest-wearing grout on the market — chemical resistant, stain resistant, no sealing needed, lasts the life of the install. The catch is a 30–45 minute pot life from mixing and a real learning curve on application; first-time DIYers usually leave a haze that requires a manufacturer-specific haze remover within 24 hours. $90–120 per quart.

See also: grout color guide

Sanded vs unsanded grout

Two cementitious grout categories — sanded has fine silica sand mixed in for grip in wider joints; unsanded is smoother for narrow joints and polished tile.

Sanded for joints 1/8 in and wider (almost all floors and most walls). Unsanded for joints under 1/8 in (mosaics) and on polished or honed marble where the sand particles scratch the tile face during the tool-off pass. Get it wrong and either the joints crack (unsanded in a wide joint) or the tile face is permanently scratched.

Grout sealer

A penetrating impregnator (Aqua Mix Sealer's Choice Gold, TileLab SurfaceGard, Miracle 511) applied to cured cementitious grout to resist water and stain absorption.

Applied 24–72 hours after grout cure, then again 1–2 times per year for a kitchen or bath. Penetrating sealer (the right kind) sits inside the grout pores and is invisible; surface sealers (the wrong kind for cured grout) leave a film and yellow over time. Urethane and epoxy grouts don't need sealing — that's most of what you're paying for.

Efflorescence

A white salt deposit that blooms on the surface of cementitious grout when soluble salts in the mortar or substrate migrate to the surface as moisture wicks through.

Most visible on dark grout, where the white bloom is dramatic against the joint color. Caused by uncured slab moisture, leaks, or efflorescence-prone aggregate; remove with a specialty efflorescence cleaner (Aqua Mix Eff-Ex) rather than acid, which etches the grout. Avoid in dark-grout installs by specifying urethane or epoxy instead of cementitious.

Wet saw

A water-cooled diamond-blade tile saw used for straight, miter, and notch cuts in porcelain, ceramic, glass, and stone.

The 7-inch home-center wet saw ($100–250 to rent for a weekend, $300–500 to buy) handles tile up to ~13 inches. For large-format (15+ in) you need a 10-inch saw with an extended rail ($800–1,500) — or a rail saw (Sigma, Rubi) that scores and snaps without water. Plan blade life around the material: ceramic blades ($30) chip on porcelain; spend on a porcelain blade ($60–120).

Score-and-snap

A manual cutter (Sigma, Rubi, QEP) that scores the tile surface with a carbide wheel, then snaps it along the score line — no water, no blade.

Fine for soft ceramic and 3×6 subway; chips and shatters on hard porcelain and glass. The advantage is dust-free, quiet operation and a clean straight edge — perfect for backsplash work where the cuts are all straight and the material is ceramic. Length-limited to the rail size (typically 24–32 in).

Nipper

A handheld carbide-jawed pliers tool used to bite small irregular cuts and curves out of a tile edge.

The go-to for fitting tile around a pipe, an outlet box corner, or any odd-shaped obstacle. Slow, leaves a rough edge that needs to be hidden under a fixture or escutcheon — for clean exposed-edge curves, a hole saw or a wet-saw rough-cut-and-grind is cleaner.

Hole saw

A diamond-coated cylindrical drill bit (1/4 in–4 in diameter) used to bore a clean circular hole through tile, glass, or stone for plumbing penetrations.

Drill at low RPM (200–400) with a steady water drip or a sponge in a tray underneath to keep the bit cool — running dry burns the diamond off and ruins a $30–60 bit in 30 seconds. Hand-held works on smaller bits; for anything 2 in or larger, use a drill stand to keep the bit perpendicular.

Miter cut

A 45° cut along the tile edge, used to create a wrapped outside corner where two tiles meet without an exposed cut edge or a metal trim piece.

The premium outside-corner detail on niches and corners — looks seamless when done right, terrible when done wrong. Requires a wet saw with a tilting cutting head and a steady hand; the finished corner is fragile, so most installers either run a thin chamfer along the meeting edge or substitute a Schluter Jolly profile for the same effect.

ANSI A108

The American National Standards Institute family of installation specifications for ceramic tile — A108.1 through A108.18 cover everything from mortar coverage to wet-area details.

If a problem arises and there's a dispute, A108 is the document. A108.5 is the mortar coverage spec (80% dry, 95% wet/exterior, 95% for large-format), A108.02 §4.3.7 sets the 15-inch threshold for medium-bed mortar, and A108.10 covers stone and natural-stone installs.

ANSI A118

The ANSI family of material specifications for the products used in tile installation — mortars (A118.1, A118.4, A118.11, A118.15), grouts (A118.6, A118.7, A118.3), and membranes (A118.10, A118.12).

The number on a bag of thinset or a bucket of grout tells you the spec it meets — A118.1 is unmodified thinset (cheap, low flex); A118.4 is modified (most common); A118.15 is medium-bed for large-format. Always read the spec, not the marketing — 'premium' on the bag means nothing without the A118 number.

TCNA Handbook

The Tile Council of North America Handbook for Ceramic, Glass, and Stone Tile Installation — the industry-standard reference for installation methods, published annually.

Every tile assembly has a TCNA method number (B412, F125, W202, etc.) that specifies the substrate, membrane, mortar, and tile combination — call out the method on the spec sheet and you've defined the install. If a setter doesn't recognize the method numbers, they aren't a working pro.

DCOF (Dynamic Coefficient of Friction)

A standardized measure of a tile's wet slip resistance, per ANSI A137.1 / ANSI A326.3.

0.42 is the floor minimum for interior wet areas (showers, bathroom floors); 0.6+ is typical for commercial entryways. Polished marble and high-gloss porcelain often fall below 0.42 wet — fine for walls and dry residential, dangerous on a shower floor unless paired with a mosaic for the grout-grid grip.

ASTM C1028

The older static coefficient of friction test for tile slip resistance, withdrawn by ASTM in 2014 in favor of the DCOF (ANSI A326.3) wet-pull test.

Still occasionally cited on older product literature with a '0.6 SCOF' number — that number is not comparable to the DCOF 0.42 minimum, and you cannot substitute one for the other. If a spec sheet only shows C1028, ask for the A326.3 DCOF before specifying.

Deflection (L/360 / L/720)

The maximum allowable mid-span movement of a structural floor under load, expressed as a fraction of the span length. L/360 is the ceramic minimum; L/720 is required for stone.

On a 16 ft floor joist span, L/360 = 16×12/360 = 0.53 in of allowed deflection; L/720 = 0.27 in. Most existing wood-framed residential floors meet L/360 but not L/720, which is why marble and natural stone often need a structural upgrade (sister joists, plywood overlay, or both) before install.

Shower pan

The waterproof base of a tiled shower — built either as a traditional mud-bed pan over a PVC liner, or as a pre-formed foam pan (Schluter Kerdi-Shower, Wedi Fundo).

Foam pans (Schluter, Wedi) have largely replaced traditional mud-pan construction on residential installs — they're sloped from the factory, install in an afternoon, and don't require the mud-bed skill that's vanishing from the trade. A traditional mud pan with PVC liner is still the only option for non-standard sizes and is what most older shower failures use.

Niche

A recessed shelf built into a tiled shower wall for soap, shampoo, and razors, framed in the rough-in and finished with tile or a stone insert.

Size to a tile module — a 12×24 niche tiles cleanly with one or two field tiles; a 13×25 niche makes you cut every piece. Place between studs (typically 14.5 in wide max), waterproof inside and out with the same membrane as the shower walls, and slope the bottom shelf 1/8 in toward the room so water doesn't pool.

Weep hole

A small opening at the base of a wall or drain assembly that allows trapped water to escape — critical in shower pans, exterior tile walls, and behind certain Schluter profiles.

The standard 2-bolt shower drain (Oatey 42213, Sioux Chief 821) has weep holes around the perimeter at the liner level; covering them with thinset during pan installation is the most common cause of shower-pan failure five years later. Verify they're protected with pea gravel or weep-hole protectors during pan setup.

Expansion / soft joint

A flexible joint of silicone caulk (rather than rigid grout) installed at any plane change, around the perimeter, and in long runs over 25 ft — per TCNA EJ171.

Soft joints absorb thermal and substrate movement that would otherwise crack rigid grout. Required at every change of plane (wall-to-floor, inside corners) and at the perimeter of any tile field; recommended every 20–25 ft on long floor runs. Use 100% silicone in a grout-matched color from the grout manufacturer (Mapei Mapesil, Laticrete Latasil) rather than generic bath caulk.

Slope-to-drain

The 1/4 in per foot minimum pitch from the perimeter of a shower floor toward the drain, required by IRC, IPC, and the TCNA Handbook.

Built into the mud bed (or the pre-sloped foam pan) before tile goes down — the tile follows the slope, the slope is not in the tile. Critical to lay out perimeter tile cuts so the slope reads symmetrical and the tile pattern doesn't fight the slope at the threshold. Smaller tile (2×2 mosaic) is much easier to slope cleanly than larger field tile.

Open time / pot life

The window between mixing thinset/grout and the point at which it skins over or hardens past usable. Cementitious thinset: ~20–30 min open time; epoxy grout: ~30–45 min pot life.

Run out of open time on thinset and the next tile won't bond to the troweled bed (skin formation blocks contact) — you scrape, re-trowel, and continue. Epoxy grout in particular punishes the slow installer; mix half batches and budget the rest of the pot life as cleanup. Hot, dry, windy conditions cut both numbers by a third.