CFI Subfloor Preparation & Assessment

Question 1

What is the maximum allowable floor flatness tolerance for most resilient flooring installations over a wood subfloor?

Accepted Answer

3/16 inch in 10 feet

Answer

Most resilient flooring manufacturers specify a flatness tolerance of no more than 3/16 inch variation over a 10-foot span.

Question 2

What minimum thickness of plywood subfloor is typically required beneath hardwood strip flooring?

Accepted Answer

3/4 inch

Answer

A 3/4-inch plywood subfloor provides the structural rigidity needed to prevent squeaks and movement under hardwood strip flooring.

Question 3

Which tool is used to detect high spots and low spots when assessing subfloor flatness?

Accepted Answer

Straightedge or flat bar

Answer

A long straightedge or flat bar is used to bridge the surface and identify deviations from flatness by revealing gaps beneath it.

Question 4

What must be done to a concrete subfloor before installing glue-down LVP if the surface has a release agent residue?

Accepted Answer

Mechanically grind or scarify the surface

Answer

Release agents prevent adhesive bonding, so the concrete must be mechanically ground or scarified to expose a clean, porous surface.

Question 5

What is the primary purpose of a self-leveling underlayment (SLU) on a concrete subfloor?

Accepted Answer

To fill low spots and achieve the required flatness tolerance

Answer

SLU is poured and flows to fill depressions, bringing the subfloor surface to the required flatness specification for flooring installation.

CFI - Flooring Installation and Maintenance Certification Practice Test