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CTI Substrate Preparation & Assessment Flashcards

6 cards from real CTI practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  1. Which test is commonly used on-site to quickly assess whether a concrete surface has been treated with a curing compound or sealer that may inhibit mortar bond?

    Answer: Water drop absorption test

    Dropping water on the concrete surface reveals sealer or curing compound presence — if water beads rather than absorbing, the surface is contaminated and must be prepared.

  2. What is the maximum height difference (lippage) allowed at transitions when a substrate is deemed flat enough for large-format tile (≥ 15 inches)?

    Answer: 1/8 inch in 10 feet

    For large-format tiles ≥ 15 inches on any side, ANSI A108.02 requires the substrate to be flat within 1/8 inch in 10 feet.

  3. What does a hollow sound when tapping a recently installed tile indicate?

    Answer: Voids beneath the tile due to insufficient mortar coverage

    A hollow or drummy sound indicates voids under the tile from inadequate mortar coverage, which reduces bond strength and risks cracking.

  4. When assessing an above-grade wood-framed floor for large-format tile (18×18 inches), what is the minimum combined subfloor and underlayment thickness typically recommended?

    Answer: 1-1/4 inches

    TCNA recommends a minimum combined thickness of 1-1/4 inches for wood subfloor assemblies under large-format tile to ensure adequate stiffness.

  5. A CTI inspector measures a concrete floor and finds it is 3/8 inch low in a 10-foot span. What is the recommended correction?

    Answer: Apply a self-leveling underlayment to bring the floor within tolerance

    A floor that is 3/8 inch low in 10 feet exceeds the 1/8-inch flatness tolerance and should be corrected with a self-leveling underlayment before tiling.

  6. What is the primary purpose of conducting a crack assessment on a concrete slab before tile installation?

    Answer: To identify moving or active cracks that require isolation or repair before tiling

    Active or moving cracks in a concrete slab will telegraph through tile and grout unless treated with a crack isolation membrane or repair, making identification critical before installation.

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Sources & references

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  1. ceramictilefoundation.org — Eligibility, fees, registration, test delivery, exam format, late registration, passing score, retake policy, score release, time limit · verified Oct 2026