CTI CTI Substrate Preparation & Assessment

Question 1

What is the maximum allowable deflection for a subfloor that will receive ceramic tile, according to the Tile Council of North America (TCNA) guidelines?

Accepted Answer

L/360

Answer

TCNA requires subfloor deflection to not exceed L/360 (span in inches divided by 360) under live load to prevent tile and grout cracking.

Question 2

Which moisture testing method measures the amount of moisture vapor emitting from a concrete slab using a sealed hood over a defined area?

Accepted Answer

Calcium chloride test

Answer

The calcium chloride test (ASTM F1869) measures moisture vapor emission rate (MVER) in pounds per 1,000 sq ft per 24 hours from a concrete slab.

Question 3

What is the maximum acceptable moisture vapor emission rate (MVER) for a concrete substrate before installing tile with a standard latex-modified thinset mortar?

Accepted Answer

8 lbs/1,000 sq ft/24 hrs

Answer

Most mortar manufacturers specify a maximum MVER of 8 lbs per 1,000 sq ft per 24 hours, though always verify with the specific product's requirements.

Question 4

A CTI inspector finds a wood subfloor with a gap of 1/4 inch between plywood panels. What is the correct assessment?

Accepted Answer

Unacceptable — gaps must not exceed 1/8 inch

Answer

TCNA guidelines require gaps between plywood subfloor panels not to exceed 1/8 inch to provide adequate support and prevent flexing at seams.

Question 5

When assessing an existing concrete slab for tile installation, which condition would require the inspector to recommend surface preparation before tiling?

Accepted Answer

A surface that is dusty or has a laitance layer

Answer

Laitance — a weak, powdery layer on concrete surfaces — must be removed by grinding or shot-blasting to ensure proper mortar bond.

CTI - Certified Tile Inspector Practice Test

CTI - Certified Tile Inspector Practice Test

CTI CTI Substrate Preparation & Assessment