NCCER Tile flashcards

31 cards. Read the term and the definition here. The deck at the top of this page is optional.

Silica dust control

Respirable crystalline silica is released when cutting, grinding, or mixing tile products. Control it with wet cutting, dust extraction, and wet cleanup; use at least an N95 respirator, and P100 or supplied air for heavy exposure.

GFCI on wet saws

A wet saw must plug into a GFCI-protected circuit to reduce shock risk from water contact. Keep the water tray above the pump intake and unplug the saw before changing blades or clearing jams.

Cement dermatitis

Portland cement mortar and grout are strongly alkaline and cause skin irritation and chemical burns with prolonged contact. Wear nitrile or barrier gloves, keep sleeves dry, and wash exposed skin promptly with water.

Tile water absorption classes

Non-vitreous tile absorbs more than 7% water, semi-vitreous 3-7%, vitreous 0.5-3%, and impervious less than 0.5%. Porcelain is generally impervious and needs a polymer-modified thinset for a reliable bond.

Material overage allowance

Order about 10% extra tile for straight-set layouts and 15-20% extra for diagonal, herringbone, or cut-heavy rooms. Keep at least one unopened box as attic stock for future repairs.

Grinder safety guard

Never remove the guard from an angle grinder or fit a blade rated below the tool's RPM. Use a diamond wheel with a dust shroud or water feed, and wear eye and hearing protection.

Substrate flatness tolerance

Thin-set tile requires the substrate to vary no more than 1/4 in. in 10 ft, with no more than 1/16 in. in any 12 in. Correct high spots by grinding and low spots with patching compound before layout.

Wood subfloor deflection

Ceramic and porcelain tile require a floor deflection limit of L/360 of the span; stone requires L/720 and a two-layer floor. Verify joist size, spacing, and span against a deflection table.

Concrete slab moisture testing

ASTM F2170 measures in-situ relative humidity and ASTM F1869 measures calcium chloride emission over 72 hours. Results must fall within the adhesive or membrane manufacturer's stated moisture limit before tile is installed.

Backer board fastening

Cement backer board is set in modified thinset and fastened with corrosion-resistant screws at the manufacturer's spacing, typically 8 in. on center. Stagger panel joints, and tape and skim joints with thinset.

Shower waterproofing height

Liquid or sheet waterproofing in a shower must extend at least 6 ft above the floor and 2 in. above the curb. Reinforce corners, seams, and penetrations with membrane banding before tiling.

Crack isolation membrane

ANSI A118.12 crack isolation membrane absorbs in-plane substrate movement and protects tile from reflective cracking. It does not correct structural deflection or substitute for a waterproof membrane.

Shower pan weep holes

Weep holes at the drain must stay open so water in the mortar bed can escape. Protect them with gravel or a weep-hole protector during the final bed, and slope the preslope to the drain.

Unmodified versus modified thinset

ANSI A118.1 dry-set mortar is unmodified; A118.4 is polymer-modified for stronger, more flexible bond. Porcelain, glass, and stone generally require A118.4 or better, and large tile needs an LHT rating.

Thinset mixing and pot life

Measure water to the bag ratio, mix, slake 5-10 minutes, then remix. Use the mortar within its stated pot life, often 2-4 hours, and discard any that has begun to set; never retemper with water.

Notch trowel selection

Match notch depth to tile size and flatness: about 1/4 x 1/4 in. for tile under 12 in., 1/4 x 3/8 in. for 12-16 in., and 1/2 x 1/2 in. for large-format tile with back-buttering.

Mortar coverage percentages

Aim for at least 80% mortar contact under tile in dry interior areas and 95% in wet areas, exteriors, and heavy-load floors. Check coverage by lifting a freshly set tile and inspecting its back.

Back-buttering large tile

Back-buttering spreads a flat layer of thinset on the tile back to fill its profile and improve contact. It is required practice for large-format tile, stone, and any tile with deep back patterns.

Expansion joint spacing

Provide at least 1/4 in. movement joints at perimeter walls, changes of plane, and regularly across large fields, commonly every 20-25 ft indoors and 8-12 ft outdoors. Fill them with sealant, never grout.

Lippage tolerance

ANSI A108.02 allows 1/32 in. of lippage for grout joints narrower than 1/4 in. and 1/16 in. for wider joints. Leveling clips, consistent mortar beds, and back-buttering reduce lippage.

Glass tile adhesive

Glass tile requires a bright white, glass-tile-rated modified thinset so the mortar does not show through the tile. Allow a longer cure before grouting, and avoid dark mortar and excessive trowel ridges.

Shelf life of thinset

Bagged cementitious thinset and grout have a limited shelf life, often about one year when kept dry. Discard bags with hardened lumps, because the cement has already begun to hydrate.

3-4-5 squaring method

Measure 3 ft along one line and 4 ft along a perpendicular line; the diagonal between the marks must be 5 ft. Multiples such as 6-8-10 work for larger rooms, and equal diagonals confirm a square layout.

Centering a tile layout

Divide the wall length by the tile-plus-joint module, then split the remainder evenly at both ends so cut tiles match. Place full tiles at the most visible wall and keep cuts wider than half a tile.

Sanded versus unsanded grout

Use sanded grout for joints 1/8 in. and wider and unsanded grout for joints narrower than 1/8 in. Unsanded grout also suits scratch-prone polished stone; epoxy grout suits high-stain or chemical exposure.

Grout joint width rules

Follow the tile manufacturer's minimum joint width: often 1/16 in. for rectified porcelain, 1/8 in. for standard ceramic, and 3/16 in. or more for stone with dimensional variation. Wider joints hide size variation.

Grout cleanup timing

Begin cleanup when grout has firmed but still yields to a thumbprint without sticking. Work the sponge in circular then diagonal strokes, rinse and change water often, and avoid over-wiping that pulls grout from joints.

Efflorescence removal

White salt deposits on grout are efflorescence, removed with a mild acid or efflorescence remover after cure. Prevent it by limiting mixing water, avoiding wet curing, and keeping the substrate dry.

Sealing grout and stone

Apply a penetrating sealer to cementitious grout and porous natural stone after full cure, often 72 hours. Wipe excess from tile faces before it dries, then buff the surface to remove haze.

Caulking changes of plane

Grout cracks at inside corners and changes of plane, so those joints are filled with flexible sealant. Use 100% silicone matched to the substrate, add backer rod where deep, and tool the joint concave.

Final tile punch list

Before turnover, check for lippage, hollow-sounding tile by tap test, consistent joint width, clean grout lines, sealed movement joints, and re-caulked wet-area corners. Correct defects before the job is accepted.