CFI Subfloor Assessment & Preparation 2

Question 1

When using a moisture meter on a concrete slab, what reading (in %RH) is the maximum acceptable level for most resilient flooring installations?

Accepted Answer

80% RH

Answer

ASTM F2170 sets 80% RH as the standard upper limit for most resilient flooring adhesive systems.

Question 2

A wood subfloor deflects excessively between joists. What is the most common corrective action before installing ceramic tile?

Accepted Answer

Sister the joists or add blocking

Answer

Sistering joists or adding blocking addresses the root structural cause of excessive deflection rather than masking it.

Question 3

Which tool is used to detect low spots and high spots across a subfloor surface?

Accepted Answer

Straightedge or floor flatness gauge

Answer

A long straightedge (typically 10 ft) reveals high and low deviations across the subfloor plane.

Question 4

What is the purpose of skim-coating a concrete subfloor with Portland cement-based filler?

Accepted Answer

To fill surface voids and achieve flatness

Answer

Skim-coating fills bug holes, trowel marks, and low spots to achieve the required flatness tolerance.

Question 5

OSB used as a subfloor panel should have its face grain oriented in which direction relative to floor joists?

Accepted Answer

Perpendicular to joists

Answer

OSB panels are engineered with the face strand oriented along the long dimension, which must span perpendicular to joists for maximum strength.

(CFI) Certified Flooring Installer Practice Test