CTI Substrate Preparation & Assessment Flashcards

Which ASTM standard governs the in-situ relative humidity testing of concrete slabs using embedded probes?

Answer: ASTM F2170

ASTM F2170 covers the standard test method for determining relative humidity in concrete floor slabs using in-situ probes.

A CTI inspector is evaluating an existing terrazzo floor as a substrate for new tile. What is the primary concern?

Answer: Terrazzo surfaces are often too smooth for mortar bond without surface preparation

Existing terrazzo is typically dense and smooth, requiring mechanical scarification or shot-blasting to create a bondable surface profile before tile installation.

What does the term 'flatness' refer to when assessing a substrate for tile installation?

Answer: The absence of high and low spots over a defined measurement length

Flatness refers to the planarity of a surface — ANSI A108.02 requires floors to be flat within 1/8 inch in 10 feet and 1/16 inch in 2 feet.

When inspecting a radiant heat slab, what additional substrate consideration is critical before tile installation?

Answer: The radiant system must be cycled (run then cool) before tiling to release residual moisture

Radiant heat slabs should be operational prior to tile installation to drive out residual moisture and allow the slab to stabilize before moisture testing.

What is the required compressive strength of a concrete substrate before tile can be installed per ANSI A108 standards?

Answer: 2,500 psi minimum

ANSI A108 requires a minimum concrete compressive strength of 2,500 psi for tile substrates to ensure adequate structural integrity.

A CTI inspector finds that a plywood subfloor panel is delaminating. What is the proper recommendation?

Answer: Replace the delaminated panels before any tile installation

Delaminated plywood panels have lost structural integrity and must be replaced entirely before tile installation, as patching will not restore adequate bond or stiffness.