CTI Tile Installation Techniques 2 — Questions and Answers
Question 1: When installing large-format tiles (24"x24" or larger), what back-buttering technique is recommended to achieve full coverage?
- Apply mortar only to the substrate
- Back-butter the tile and comb the substrate for 95% contact (Correct answer)
- Apply a thin skim coat to the tile back only
- Use a notched trowel on the tile back with no substrate mortar
Correct answer: Back-butter the tile and comb the substrate for 95% contact
Large-format tiles require both back-buttering the tile and combing the substrate to achieve the minimum 95% mortar contact required by ANSI A108.02.
Question 2: What is the correct method for cutting an inside corner notch in a ceramic wall tile?
- Score with a glass cutter and snap
- Use a wet saw to make two straight cuts forming the notch (Correct answer)
- Use tile nippers only
- Use an angle grinder with a diamond blade from both faces
Correct answer: Use a wet saw to make two straight cuts forming the notch
A wet saw allows precise straight cuts; two intersecting cuts create a clean inside corner notch without cracking the tile body.
Question 3: When installing tile in a steam shower, which membrane application method is required at inside corners?
- Butt the membrane sheets tightly together
- Overlap membrane sheets by at least 2 inches and apply sealant (Correct answer)
- Apply caulk bead only, no membrane overlap needed
- Leave a 1/8" expansion gap and grout over it
Correct answer: Overlap membrane sheets by at least 2 inches and apply sealant
In steam showers, membrane sheets must overlap at least 2 inches at corners and be sealed to prevent moisture infiltration under high heat and humidity.
Question 4: A tile installer is setting mosaic tile on a mesh backing. What is the primary concern when applying mortar to the substrate?
- Using a fine-ribbed trowel so mortar fills each mesh cell without squeezing between tiles (Correct answer)
- Applying mortar as thick as possible to embed the mesh deeply
- Using an unmodified mortar to prevent the mesh from bonding too strongly
- Scoring the substrate before applying mortar
Correct answer: Using a fine-ribbed trowel so mortar fills each mesh cell without squeezing between tiles
A fine-ribbed trowel ensures mortar contacts each small tile without oozing into the joints, maintaining clean grout lines on mesh-mounted mosaics.
Question 5: Which of the following best describes the float method for applying grout on a wall tile installation?
- Press grout diagonally across joints using a rubber float, then clean residue in circular motions (Correct answer)
- Apply grout with a margin trowel and tool each joint individually
- Pour liquid grout across the surface and spread with a squeegee
- Apply grout with a grout bag and pack each joint separately
Correct answer: Press grout diagonally across joints using a rubber float, then clean residue in circular motions
The float method involves holding the rubber float at a 30–45° angle, pressing grout diagonally across joints, then removing excess with circular motions.
Question 6: When installing exterior tile on a deck, why must the tile surface be sloped?
- To improve aesthetics and visual alignment
- To drain water away from the structure and prevent pooling (Correct answer)
- To compensate for uneven substrate thickness
- To allow for thermal expansion of the tile field
Correct answer: To drain water away from the structure and prevent pooling
Exterior deck tile must slope a minimum of 1/4" per foot toward drains or edges to prevent water from pooling, which causes freeze-thaw damage and mortar failure.
Question 7: What is the purpose of using a beating block and rubber mallet during tile installation?
- To fracture weak tiles before installation
- To seat tiles firmly and evenly into the mortar bed, eliminating voids (Correct answer)
- To compact the mortar substrate before tile placement
- To adjust grout lines after the mortar has set
Correct answer: To seat tiles firmly and evenly into the mortar bed, eliminating voids
A beating block distributes mallet force evenly across the tile face, fully embedding it into mortar and eliminating hollow spots without cracking the tile.
CTI Tile Installation Techniques 2
When installing large-format tiles (24"x24" or larger), what back-buttering technique is recommended to achieve full coverage?