CFI Subfloor Preparation & Assessment 1 — Questions and Answers
Question 1: What is the maximum allowable floor flatness tolerance for most resilient flooring installations over a wood subfloor?
- 3/16 inch in 10 feet (Correct answer)
- 1/4 inch in 6 feet
- 1/8 inch in 3 feet
- 1/2 inch in 10 feet
Correct answer: 3/16 inch in 10 feet
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?
- 3/4 inch (Correct answer)
- 1/2 inch
- 5/8 inch
- 1 inch
Correct answer: 3/4 inch
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?
- Straightedge or flat bar (Correct answer)
- Moisture meter
- Chalk line only
- Laser level only
Correct answer: Straightedge or flat bar
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?
- Mechanically grind or scarify the surface (Correct answer)
- Apply a bonding primer only
- Wet mop with a degreaser and install immediately
- Sand with 60-grit paper
Correct answer: Mechanically grind or scarify the surface
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?
- To fill low spots and achieve the required flatness tolerance (Correct answer)
- To add a moisture barrier
- To increase subfloor thickness
- To reduce noise transmission
Correct answer: To fill low spots and achieve the required flatness tolerance
SLU is poured and flows to fill depressions, bringing the subfloor surface to the required flatness specification for flooring installation.
Question 6: Before installing flooring over a radiant heat subfloor, what must the installer verify first?
- That the system has been run through a heating cycle and the surface temperature is within acceptable limits (Correct answer)
- That the thermostat is set to maximum
- That all pipes are copper
- That the underlayment is foam
Correct answer: That the system has been run through a heating cycle and the surface temperature is within acceptable limits
The radiant heat system should be cycled before installation so moisture is driven out of the concrete and the slab reaches a stable temperature.
CFI Subfloor Preparation & Assessment 1
What is the maximum allowable floor flatness tolerance for most resilient flooring installations over a wood subfloor?