CFI Adhesive & Underlayment Selection 4 — Questions and Answers
Question 1: When applying adhesive in a large area, an installer notices it is 'stringing' excessively. What does this indicate?
- The adhesive has too much moisture and should be discarded
- The adhesive has reached peak grab and flooring should be laid immediately (Correct answer)
- The adhesive is too cold and needs to warm to room temperature
- The trowel notch is too small
Correct answer: The adhesive has reached peak grab and flooring should be laid immediately
Excessive stringing (long threads when the trowel is lifted) indicates the adhesive has developed high grab and is approaching the end of its open time, signaling the installer to place flooring promptly.
Question 2: What is the minimum compressive strength typically required for underlayment panels used under ceramic tile in residential applications?
- 500 psi
- 1,000 psi
- 3,000 psi (Correct answer)
- 6,000 psi
Correct answer: 3,000 psi
Underlayment panels used under ceramic tile in residential settings should have a minimum compressive strength of approximately 3,000 psi to prevent deflection under load that would crack tile and grout.
Question 3: A customer requests a floating engineered hardwood installation over existing 3/4" hardwood. What underlayment consideration is most important?
- Use the thickest underlayment available for maximum comfort
- Verify total finished floor height does not exceed clearances at doors and transitions (Correct answer)
- Install no underlayment to keep the floor as low as possible
- Use a rubber-based underlayment for maximum moisture protection
Correct answer: Verify total finished floor height does not exceed clearances at doors and transitions
Adding both new flooring and underlayment over existing hardwood increases overall floor height, which must be checked against door clearances, transitions, and appliance spaces.
Question 4: Which adhesive system is specifically engineered for installing cork flooring tiles?
- Epoxy two-part adhesive
- Water-based contact adhesive formulated for cork (Correct answer)
- Solvent-based neoprene contact cement
- Urethane wood flooring adhesive
Correct answer: Water-based contact adhesive formulated for cork
Water-based contact adhesives formulated for cork provide the necessary bond to the open-cell cork surface without damaging it or releasing harmful solvents into the porous material.
Question 5: When selecting underlayment for a luxury vinyl plank (LVP) floor, what property should the installer prioritize?
- Maximum thickness for best feel underfoot
- Flatness and firmness to maintain the integrity of locking joints (Correct answer)
- High R-value for thermal insulation
- Ability to compress fully under heavy furniture
Correct answer: Flatness and firmness to maintain the integrity of locking joints
LVP click-lock joints require a firm, flat underlayment because excessive compression or unevenness causes the joints to open, squeak, or fail prematurely.
Question 6: A job site has an ambient temperature of 55°F. How does this affect adhesive performance?
- It has no effect if the adhesive is applied quickly
- Cold temperatures slow adhesive cure and can extend open time unpredictably (Correct answer)
- Cold temperatures cause adhesive to cure faster than normal
- Low temperature improves adhesive bond strength
Correct answer: Cold temperatures slow adhesive cure and can extend open time unpredictably
Cold temperatures slow the chemical or evaporative curing process of most flooring adhesives, extending open time and delaying the achievement of full bond strength.
Question 7: What does the term 'wet lay' installation mean when referring to adhesive application?
- Applying adhesive and immediately placing the flooring before any open time (Correct answer)
- Flooding the substrate with adhesive before troweling
- Installing flooring over a recently cleaned wet substrate
- Applying adhesive to both the substrate and the back of the flooring material
Correct answer: Applying adhesive and immediately placing the flooring before any open time
Wet lay means placing flooring immediately into fresh, wet adhesive without waiting for any open time, which is required by certain flooring types or specific adhesive systems.
CFI Adhesive & Underlayment Selection 4
When applying adhesive in a large area, an installer notices it is 'stringing' excessively.
What does this indicate?