The layout plan and material selection for a tile installation determine both the aesthetic outcome and the long-term performance. A tile job that looks beautiful on day one but uses the wrong thinset for the substrate, incorrect grout for the joint size, or fails to maintain adequate mortar coverage behind large-format tiles will develop problems that are expensive to fix. Knowing what to ask about both the design decisions and the technical specifications is how you get an installation that performs as well as it looks.

“The mortar coverage question is one most homeowners never ask and one every professional tile setter should be thinking about constantly. ANSI A108 requires 80% coverage on floor tile and 95% coverage in wet areas. Below that threshold, you get hollow spots, tiles that crack under point load, and in showers, water finds its way under the tile through those voids. Lift a tile five minutes after you set it and look at the back — that’s how you verify coverage. A tile setter who does that test isn’t just following standards; they’re doing quality work.”

— Adaeze Nwosu, certified tile installer and member of the Terrazzo Tile and Marble Association of your country with 17 years of experience in residential and commercial tile installation in the local area

Layout Questions

a white tiled floor

Will you show me the layout plan before any tile is set?

Ask the setter to establish the layout on the actual surface before any adhesive is applied — using chalk lines, laser level, or dry-laid tiles. Confirm:

Starting point: Where is the layout centered? For a shower, typically centered on the main wall. For a bathroom floor, typically centered in the doorway or on the most visible sightline. For a kitchen backsplash, typically centered on the range hood or the most prominent feature.

Edge cuts: Where do cuts fall at the perimeter? Cuts should be at least half a tile width and should be roughly equal on opposite walls. Slivers of tile (less than 1/3 tile width) at the edge look unfinished.

Pattern alignment: For a stacked or offset pattern, the layout determines how grout joints align across the room.

Focal point: For a decorative tile or feature wall, the layout is built around the feature element.

What a good answer looks like: The setter establishes chalk lines or dry-lays tiles before beginning, shows you where cuts will fall, and confirms your approval before any adhesive is applied.

For large-format tile: how will lippage be controlled?

Lippage is the difference in height between adjacent tiles — one tile edge sitting higher than its neighbor. It’s more pronounced with large-format tile and can be both a trip hazard and an aesthetic defect.

Controlling lippage requires:
– A flat substrate (within 1/8″ over 10 feet for tiles larger than 15″)
– Correct thinset application technique (back-buttering the tile in addition to troweling the substrate)
– Tile leveling systems (clip-and-wedge systems that hold tiles in plane while the mortar sets)

Ask whether a tile leveling system will be used for large-format tile installations.

For a herringbone, chevron, or other complex pattern: how will the layout be established?

Complex patterns require more detailed layout planning. Ask the setter to show you the specific layout approach and confirm how the pattern will be centered and how cuts at the perimeter will be handled.

Thinset Mortar Questions

Elegant bathroom with modern fixtures and beige tiles.

What thinset are you using, and why is it appropriate for this tile and substrate?

Thinset specification varies by application:

Polymer-modified thinset (most residential applications):
Contains polymer additives that improve bond strength, flexibility, and water resistance. Required for wet areas and recommended for most applications. Look for ANSI A118.4 or A118.11 classification on the bag.

Medium-bed mortar (for large-format tile):
Standard thinset is designed to be applied at 3/16″ to 1/4″ thickness. Large-format tile (typically anything over 12″x12″) often requires more mortar to span minor substrate variations — medium-bed mortars are formulated to resist sag at thicker applications. Ask whether medium-bed mortar is being used for any tile larger than 12″x12″.

Back-buttering: For large-format tile, applying a skim coat of thinset to the back of the tile (in addition to the troweled substrate) significantly improves coverage and bond. Ask whether back-buttering is part of the installation practice for large tiles.

ANSI A118.15 (highly polymer modified): Required for some specialty applications — glass tile, natural stone tile that’s moisture-sensitive, or tile over radiant heat systems. Ask whether your specific tile requires this level of adhesive.

What mortar coverage will be achieved?

ANSI A108 (the standard for tile installation) specifies:
– Floor tile: Minimum 80% mortar coverage
– Wet areas (showers, tub surrounds): Minimum 95% mortar coverage
– Exterior tile: Minimum 95% coverage

Coverage below these thresholds leaves voids under tiles — which become hollow-sounding spots, potential tile cracking under point loads, and in wet areas, pathways for water to infiltrate behind the tile.

Ask specifically: how will you verify mortar coverage? A professional setter checks coverage by periodically lifting a freshly set tile and examining the back — looking for at least 80% (or 95% in wet areas) of the tile back covered with mortar.

What a good answer looks like: A described coverage verification practice — lifting tiles periodically to check the back.

Grout Questions

What grout are you specifying for each area?

Sanded grout (for joints 1/8″ and wider):
Contains sand aggregate. More porous than epoxy. Should be sealed after installation and periodically thereafter. Appropriate for most floor applications.

Unsanded grout (for joints narrower than 1/8″):
No sand aggregate. Used on polished stone (sand scratches polished surfaces) and for very narrow joints. Less durable than sanded grout.

Epoxy grout:
Two-component epoxy system. Stain-resistant, color-consistent, essentially impervious to water. Most durable option. More expensive and more technically demanding to install — must be mixed properly and worked quickly before curing. The preferred grout for shower applications.

Modified grout (polymer-enhanced sanded or unsanded):
Polymer additives improve stain and water resistance over standard grout. A good middle ground in performance and cost.

Ask what grout is specified for each area and whether sealing is required and included.

Will the grout be sealed, and when?

Most sanded grouts require sealing after curing to improve stain and water resistance. Ask:

  • Is sealing included in the scope?
  • What sealer product is being used?
  • When should the grout be sealed? (Typically after the grout has fully cured — often 72 hours minimum)
  • How often should the grout be resealed? (Typically every 1–3 years depending on the sealer and usage)

Epoxy grout does not require sealing.

Questions About Tile Selection and Suitability

Is this tile rated for the intended application?

Not all tiles are suitable for all applications. Key rating systems:

PEI wear rating (for glazed tile):
– PEI 1–2: Wall tile only
– PEI 3: Standard residential floors
– PEI 4: Heavy residential and light commercial floors
– PEI 5: Heavy commercial floors

DCOF (Dynamic Coefficient of Friction):
For wet area floor applications, tile must meet minimum slip resistance requirements. The standard for wet residential floors is DCOF ≥ 0.42. Ask whether the proposed floor tile meets this requirement.

Frost resistance:
For exterior applications in many regions’s freeze-thaw climate, tile must be frost-resistant (vitrified or porcelain, not porous ceramic). Ask whether exterior tile is frost-rated.

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