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CTI Substrate Preparation & Waterproofing 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.

Read the first 6 CTI Substrate Preparation & Waterproofing flashcards as text

  1. What is the minimum thickness of a Portland cement mortar bed for a floor tile installation per TCNA standards?

    Answer: 3/4 inch

    TCNA specifies a minimum mortar bed thickness of 3/4 inch for floor installations to provide adequate structural support.

  2. Which ASTM standard governs the in-situ relative humidity probe test for concrete slab moisture?

    Answer: ASTM F2170

    ASTM F2170 covers the in-situ relative humidity probe test, where probes are inserted into drilled holes in the slab.

  3. How should a CTI inspector recommend correcting a substrate with excessive high spots and low spots before tiling?

    Answer: Grind high spots and fill low spots with patching compound

    Both high spots must be ground down and low spots filled to achieve a flat substrate meeting the required tolerance.

  4. What is the maximum substrate flatness tolerance for large-format tiles with any side 15 inches or longer?

    Answer: 1/8 inch in 10 feet

    TCNA recommends no more than 1/8 inch variation in 10 feet for large-format tiles to prevent visible lippage.

  5. What material is typically used to bond a secondary waterproofing membrane to a substrate around shower niches and corners?

    Answer: Thinset mortar per the membrane manufacturer's specifications

    The membrane manufacturer specifies the bonding material — typically unmodified or modified thinset — to ensure compatibility and maintain warranty coverage.

  6. Most crack isolation membranes are rated to accommodate existing substrate cracks up to what maximum width?

    Answer: 1/8 inch

    Most crack isolation membranes accommodate cracks up to 1/8 inch wide without transferring movement stress to the tile surface.

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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