WLFI Adhesive Selection & Application 2 — Questions and Answers
Question 1: When installing engineered wood flooring over a radiant heat subfloor, which adhesive property is most critical?
- High initial tack
- Flexibility and heat resistance (Correct answer)
- Rapid cure time
- Solvent-based formula
Correct answer: Flexibility and heat resistance
Adhesives used over radiant heat must remain flexible and withstand elevated temperatures without losing bond strength.
Question 2: A moisture vapor emission rate (MVER) of 8 lbs/1,000 sq ft/24 hrs is measured on a concrete slab. What is the correct action before adhesive application?
- Proceed with a standard urethane adhesive
- Apply a moisture-tolerant adhesive rated for that MVER
- Install a vapor retarder membrane first (Correct answer)
- Let the slab dry for 48 hours then retest
Correct answer: Install a vapor retarder membrane first
An MVER of 8 lbs exceeds the threshold for most adhesives, requiring a vapor retarder membrane before bonding.
Question 3: Which trowel notch size produces a heavier adhesive deposit suitable for filling minor subfloor irregularities?
- V-notch 1/16"
- U-notch 1/8"
- Square-notch 1/4" (Correct answer)
- Fine-tooth 1/32"
Correct answer: Square-notch 1/4"
A 1/4" square-notch trowel lays down more adhesive, helping fill minor surface voids in the subfloor.
Question 4: What is the primary reason an inspector checks for adhesive bleed-through at flooring joints?
- It indicates insufficient adhesive was applied
- It causes joint staining and prevents proper expansion (Correct answer)
- It shows the adhesive cured too slowly
- It is a sign of excessive subfloor moisture
Correct answer: It causes joint staining and prevents proper expansion
Adhesive bleed-through into joints stains the finish surface and fills expansion gaps, which can cause buckling.
Question 5: Which condition would cause a pressure-sensitive adhesive to fail prematurely when bonding resilient laminate flooring?
- Low ambient humidity
- Substrate surface contamination with dust or oil (Correct answer)
- Correct open time observed
- Proper trowel notch used
Correct answer: Substrate surface contamination with dust or oil
Dust, oil, or contaminants on the substrate prevent pressure-sensitive adhesives from forming a proper bond.
Question 6: An epoxy adhesive is selected for a wood floor installation. What characteristic distinguishes it from urethane adhesives?
- It remains permanently flexible after cure
- It consists of two components mixed at the job site (Correct answer)
- It is water-based and low VOC
- It requires a longer open time
Correct answer: It consists of two components mixed at the job site
Epoxy adhesives are two-part systems (resin + hardener) mixed on site, producing a rigid, high-strength bond.
Question 7: During inspection, a wood floor installed with urethane adhesive shows widespread telegraphing of adhesive ridges. What was the most likely installation error?
- Using too little adhesive
- Failing to collapse adhesive ridges before laying planks (Correct answer)
- Allowing insufficient open time
- Using the wrong trowel angle
Correct answer: Failing to collapse adhesive ridges before laying planks
Urethane adhesive ridges must be spread or collapsed before planks are set to prevent telegraphing through the floor surface.
WLFI Adhesive Selection & Application 2
When installing engineered wood flooring over a radiant heat subfloor, which adhesive property is most critical?