CFI Tile & Stone Installation 4 — Questions and Answers
Question 1: According to the TCNA Handbook, what is the maximum allowable deflection for a subfloor intended for ceramic tile installation?
- L/120
- L/180
- L/360 (Correct answer)
- L/600
Correct answer: L/360
The TCNA requires floor deflection not to exceed L/360 of the span length under live load for ceramic tile installations.
Question 2: What is the primary reason diagonal tile layouts require more tile material than straight layouts?
- Diagonal tiles are cut thicker at the factory
- More cuts are needed at the perimeter, increasing waste (Correct answer)
- Diagonal patterns use larger tiles
- Adhesive coverage is lower for diagonal installations
Correct answer: More cuts are needed at the perimeter, increasing waste
Diagonal layouts create angled cuts at all four walls, generating significantly more cut waste than straight grid patterns.
Question 3: When mixing Portland cement mortar for a wall application, what is the correct Portland cement to sand ratio?
- 1:1
- 1:3 to 1:5 (Correct answer)
- 1:6 to 1:8
- 1:10
Correct answer: 1:3 to 1:5
A 1:3 to 1:5 Portland cement to sand ratio is standard for scratch and brown coats on wall applications.
Question 4: What does the term 'back-buttering' refer to in tile installation?
- Applying mortar to the back face of the tile before setting (Correct answer)
- Applying butter wax to the substrate for release
- Smoothing the substrate with a flat trowel
- Applying sealant to the back of stone tiles
Correct answer: Applying mortar to the back face of the tile before setting
Back-buttering is the technique of spreading a thin coat of mortar on the back of a tile to improve bond and coverage.
Question 5: Which substrate is NOT suitable as a direct bond surface for ceramic tile without additional preparation?
- Concrete slab
- Cement backer board
- Existing vinyl flooring (Correct answer)
- Mortar bed
Correct answer: Existing vinyl flooring
Vinyl flooring is too flexible and non-porous for direct tile bonding without proper surface preparation or removal.
Question 6: When installing tile in a steam shower, what type of waterproofing assembly is required?
- Standard cement board with latex paint
- Moisture-resistant drywall (greenboard)
- Continuous waterproof membrane rated for steam environments (Correct answer)
- Two layers of 15-lb felt paper
Correct answer: Continuous waterproof membrane rated for steam environments
Steam showers generate pressurized moisture that requires a continuous, steam-rated waterproof membrane throughout the entire assembly.
Question 7: What is 'efflorescence' and how does it commonly appear in tile and stone installations?
- A type of adhesive failure appearing as tile lifting
- White powdery deposits on grout or stone surfaces caused by salt migration (Correct answer)
- Dark staining from mold growth behind tiles
- Cracking in tiles caused by thermal expansion
Correct answer: White powdery deposits on grout or stone surfaces caused by salt migration
Efflorescence occurs when water carries soluble salts to the surface, leaving white deposits as the water evaporates.
CFI Tile & Stone Installation 4
According to the TCNA Handbook, what is the maximum allowable deflection for a subfloor intended for ceramic tile installation?