ACT Large Format Tile flashcards

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

Substrate flatness tolerance

For large format tile, the substrate should typically be flat within 1/8 in. in 10 ft and 1/16 in. in 24 in. from the required plane; confirm the project's governing standard.

Concrete moisture vapor limit

Common limits are 3-5 lb per 1000 sq ft per 24 hr vapor emission and 75-80% relative humidity by probe; the adhesive manufacturer's limit governs and must be met before covering.

Concrete surface profile CSP

CSP 3-5 is the typical profile for thin-set bonding to concrete; CSP 1-2 is too smooth and requires mechanical profiling such as grinding or scarifying before tile installation.

Floor deflection for LFT

Floor systems for large format tile typically require L/360 minimum for ceramic and porcelain, and L/480 or stiffer for stone; verify the governing standard and tile manufacturer's requirement.

Bond-breakers on substrate

Curing compounds, sealers, paint, adhesive residue, and loose material prevent mortar bond; they must be removed by mechanical or chemical means before any tile is set.

ANSI A118.4 mortar

A118.4 is the standard for modified dry-set (polymer-modified) mortar; it is commonly required for large format tile because it provides improved bond and flexibility over unmodified mortar.

ANSI A118.15 mortar

A118.15 is the improved modified mortar standard with higher performance requirements than A118.4, including better bond strength and shear resistance for demanding installations.

Mortar coverage requirement

Large format tile requires at least 90% mortar coverage in dry areas and 95% in wet areas, with full support at corners and edges; verify by lifting a set tile.

Mortar open time

Open time is how long troweled mortar stays workable before it skins over; if the surface skins before tile placement, bond is compromised and the mortar must be re-troweled.

Back-buttering tile

Back-buttering is applying a thin layer of mortar to the tile back before setting; it improves coverage and reduces lippage on large format tile, especially over uneven substrates.

Pot life of mortar

Pot life is the working time after mixing; adding water to re-temper mortar that has begun to set changes the mix ratio and weakens the bond, so it must not be done.

3-4-5 squaring method

Measure 3 ft along one line and 4 ft along a perpendicular line; if the diagonal is 5 ft, the lines are square. Use this to verify layout reference lines before setting tile.

Grid layout for LFT

A grid layout uses repeated control lines to keep courses aligned across large fields; it controls cumulative drift better than a single center line, which is important for large format tile.

Minimizing narrow cuts

Plan layout so cuts at walls and openings are at least half a tile wide where possible; narrow slivers are visually poor and difficult to cut and set accurately.

Blending cartons of tile

Pull tile from multiple cartons during installation to distribute shade and caliber variation across the field; large format tile can vary noticeably between production runs.

Combing mortar direction

Comb mortar in one direction and set tile perpendicular to the ridges, or back-butter, so trapped air can escape and full contact is achieved under the tile.

Embedding LFT by beating

Use a rubber mallet or beating block to embed large format tile into the mortar; avoid excessive force that can crack thin large tiles, and check coverage periodically.

Consistent joint width

Use spacers or a leveling system to hold a consistent joint width; small errors compound across a large field, so eye-balling joint width is unreliable for large format tile.

Slump control on walls

Large wall tiles can slump before the mortar sets; use a ledge or support and a mortar with a non-sag rating to hold the tile in position until cure.

Lippage definition

Lippage is the difference in height between adjacent tile surfaces; the acceptable limit is typically 1/32 in. plus the tile's allowable warpage, per the governing standard.

Tile warpage and lippage

Warpage is the tile's own curvature; it contributes to lippage and must be accounted for in layout and leveling, especially with rectified edges and narrow joints.

Leveling system function

Clips and wedges or spin caps hold adjacent tiles to a common plane while mortar sets; they maintain the plane but cannot correct a substrate that is out of flatness.

Removing leveling clips

Remove clips and wedges only after the mortar has set enough to hold the tile, per the system's instructions; removing too early allows the tile to move and lippage to return.

Perimeter movement joint

Leave a gap of typically 1/4 in. minimum at walls and fixed objects, filled with a compressible sealant rather than grout, to allow tile and structure to move.

Flexible sealant in joints

Movement joints must be filled with a flexible sealant that bonds to the joint sides and remains compressible; rigid grout in a movement joint will crack or cause tile failure.

Aligning movement joints

Movement joints must align with structural joints, concrete control joints, and changes in substrate or plane; they must be continuous through the tile field and not bridged.

Waterproofing in wet areas

Showers, tub surrounds, and exterior areas require a waterproofing membrane over the substrate before tile; tile and grout are not waterproof and do not substitute for a membrane.

Shower pan slope

The shower pan must slope to the drain, typically 1/4 in. per foot, and the drain must be integrated with the waterproofing membrane to direct water to the drain.

Flood test procedure

Plug the drain and fill the pan with water to the top of the curb or a marked level, typically for 24 hours, to verify the waterproofing membrane is watertight.

Wet saw blade selection

Use a continuous-rim diamond blade rated for the material; a blade suited to porcelain and stone reduces chipping and cuts accurately on large format tile.

Silica dust control

Cutting, grinding, and drilling tile and concrete generate respirable crystalline silica; use wet methods, dust collection, and respiratory protection per OSHA requirements.

ANSI A108.19 standard

ANSI A108.19 covers installation of large format tile; it is referenced alongside the TCNA Handbook methods that provide installation details by substrate and application.