NCCER Tile key terms

A dry-set bonding material of portland cement, sand, and polymer additives that is mixed with water and used to attach tile to stable substrates. It cures by hydration and offers more flexibility and bond strength than unmodified thinset.

A general shop term for cementitious tile adhesive applied in a thin layer with a notched trowel. It is not a brand name and may be modified or unmodified; the bag label and ANSI standard determine its actual performance class.

The ANSI standard covering modified dry-set cement mortar, meaning a cement mortar with polymer additions that improve bond and flexibility. It is the common specification cited for latex-modified thinset on interior floors and walls.

The ANSI standard for dry-set cement mortar used to bond tile to exterior-grade plywood. It requires higher bond strength than standard modified mortar and is the reference for plywood-over-joist installations.

The ANSI standard for waterproof membranes for thin-set ceramic tile and dimensional stone. Products meeting it are used in showers, wet areas, and steam rooms to stop water from reaching the substrate.

A flat steel trowel with square, U-shaped, or V-shaped teeth that combs adhesive into parallel ridges of controlled depth. Tooth size and shape must match tile size and substrate so coverage reaches the required percentage.

The percentage of the tile back actually in contact with adhesive after pressing. Interior dry areas typically require 80 percent, while wet areas, exteriors, and large-format tile require 95 percent or full contact with no voids at corners and edges.

Spreading a thin, flat layer of adhesive on the back of a tile before setting it into the combed bed. It improves bond, fills the tile's back profile, and is required practice for large-format tile and for exterior or wet-area work.

A tile with at least one edge of 15 inches or more. These pieces need flat substrates, a mortar bed thick enough to compensate for minor variation, back-buttering, and often a suction-cup or frame lifting tool to place them accurately.

A height difference between the edges of two adjacent tiles. Acceptable limits are set by the project specification or tile standard; excessive lippage is a common cause of complaint and inspection failure, especially with large-format tile and offset patterns.

The natural bow, twist, or curvature built into a tile during manufacturing. Warpage makes it impossible for two tiles to sit perfectly flush along a long edge, so it must be considered when choosing joint width and offset layout.

A small plastic or rubber device inserted between tiles to hold a consistent joint width while the adhesive cures. Spacers are removed before grouting unless the design calls for a joint of that exact width.

A reusable system of clips and wedges or caps that pulls adjacent tile edges into the same plane during curing. It reduces lippage in large-format and offset installations but does not replace a flat substrate or proper mortar coverage.

The gap left between tiles that is later filled with grout. Joint width must be at least three times the tile's warpage and wide enough to accept grout; narrow joints in wet areas are hard to fill completely.

A cementitious or epoxy material used to fill joints between tiles. Cement grout is mixed with water and may be sanded or unsanded; epoxy grout is a two-part chemical-cure product used where stain resistance or chemical resistance is needed.

A cement grout containing silica sand aggregate, used for joints about 1/8 inch and wider. The sand adds strength and reduces shrinkage cracking; it can scratch polished stone and soft glazed surfaces, so it is not used there.

A cement grout with no sand aggregate, used for narrow joints up to about 1/8 inch and for scratch-sensitive surfaces such as polished stone. It shrinks more than sanded grout, so wide joints may crack.

A two-part resin and hardener grout that cures by chemical reaction rather than by drying. It resists stains, acids, and water, needs no sealing, and is common in food service, commercial kitchens, and demanding wet areas.

A temporary coating applied to tile faces before grouting to keep cement grout from sticking in surface texture or pores. It is especially useful on unglazed, quarry, and some stone tile and is washed off after the grout sets.

A thin film of cement residue left on the tile face after grouting. It is removed with clean water and a damp sponge during initial cleanup and with a haze remover after curing; dried haze is much harder to remove.

A sheet or liquid-applied layer that stops water vapor and liquid water from passing into the substrate. In showers it is installed over the substrate and tied into the drain and wall junctions to form a continuous barrier.

A flexible PVC or CPE sheet placed under the mortar bed of a shower floor to collect water and direct it to the drain weep holes. It must slope to the drain and lap over the curb and up the walls.

A sloped mortar bed placed under the shower pan liner so water that passes through the tile and setting bed drains to the weep holes. It is typically 1/4 inch per foot and is separate from the finished mortar bed above the liner.

Small openings in the clamping ring of a shower drain that let water trapped above the pan liner escape into the drain. They must be kept open and clear of mortar or grout during installation.

A thick bed of sand and portland cement mortar, typically 1 to 2 inches, used to create a level or sloped setting surface. It can be bonded to a slab or placed over a cleavage membrane on a wood subfloor.

A sheet of building paper or plastic placed between a wood subfloor and a reinforced mortar bed to keep the bed from bonding and to allow it to move independently. It also protects the wood from moisture in the mortar.

A diamond-mesh galvanized sheet fastened over a cleavage membrane or sheathing to reinforce mortar and give it a mechanical key. It is required for mortar beds over wood framing and for many wall applications.

A rigid tile substrate made of cement and aggregate with a fiberglass mesh face. It is fastened to framing with corrosion-resistant screws and its joints are taped and filled with mortar before tiling.

Exterior-glue, interior-grade plywood used as a tile substrate only when the adhesive is rated for it, such as A118.11 mortar. It must be at least 5/8 inch, properly supported, and free of deflection beyond L/360.

The amount a floor structure bends under load, expressed as a fraction of span such as L/360. Tile requires a stiff floor; excessive deflection cracks tile and grout, so joist size, spacing, and span must be checked before tiling.

A deliberate gap that lets tile and substrate move without cracking. It is placed at perimeters, over structural joints, and at intervals in large fields, and is filled with a flexible sealant rather than rigid grout.

A general term for joints that accommodate movement, including expansion, contraction, and control joints. They must be carried through the tile layer and filled with a compressible backer and sealant compatible with the tile.

The period during which cement mortar or grout gains strength through hydration. Fresh tile work must be protected from traffic, freezing, and rapid drying; rushing this stage causes weak bond and powdery grout.

The gear required for tile work, including safety glasses, gloves, hearing protection, and a NIOSH-approved respirator when cutting or mixing silica-containing materials. Silica dust is a serious lung hazard and wet cutting or dust collection is preferred.

Fine crystalline particles released when cutting, grinding, or mixing concrete, mortar, and tile. Prolonged exposure can cause silicosis, so work should use wet methods, local exhaust, and respiratory protection as required by OSHA.

A motorized tile saw with a water-cooled diamond blade that cuts tile accurately while suppressing dust. The water tray and pump must be kept clean and filled, and the blade guard and GFCI protection must be in place.

A material or surface that prevents adhesive or mortar from sticking, such as plastic sheet, tar paper, or a release agent. It is used where tile must move independently of the substrate, as in a floating mortar bed.

A chalk or pencil reference line snapped on the substrate to control tile position and squareness. Layout lines are established from the room's centerlines or primary sight lines so that cut tiles at edges are balanced and full tiles dominate.

A straight board marked with the actual course heights of tile and grout joints. It is used to check layout, count courses, and transfer elevations to walls without repeated measuring, especially on vertical work.