WLFI Installation Standards & Techniques 3 — Questions and Answers
Question 1: When installing engineered hardwood over a concrete slab, which installation method is NOT typically recommended by manufacturers?
- Glue-down
- Floating
- Staple-down
- Nail-down (Correct answer)
Correct answer: Nail-down
Traditional nail-down installation is not used over concrete because nails cannot penetrate concrete properly; glue-down, floating, or staple-down (over sleepers) are the accepted methods.
Question 2: According to ASTM F710, what is the minimum on-center spacing requirement for floor flatness measurements when evaluating a concrete subfloor for hardwood installation?
- 3-foot radius
- 6-foot radius (Correct answer)
- 10-foot radius
- 12-foot radius
Correct answer: 6-foot radius
ASTM F710 requires flatness to be measured within a 6-foot radius, with no more than 3/16" variation, to ensure the subfloor is suitable for hardwood installation.
Question 3: During a hardwood installation inspection, an inspector finds that staggered end joints between adjacent rows are only 2 inches apart. This violates the typical minimum stagger requirement of:
- 4 inches
- 6 inches (Correct answer)
- 8 inches
- 10 inches
Correct answer: 6 inches
Most manufacturers and NWFA standards require end joints in adjacent rows to be staggered a minimum of 6 inches to prevent H-joint patterns and ensure structural integrity.
Question 4: What is the purpose of back-rolling adhesive when performing a glue-down hardwood installation?
- To seal the concrete before adhesive application
- To ensure uniform adhesive transfer to the back of each plank (Correct answer)
- To remove excess adhesive from the surface
- To flatten ridges in the concrete subfloor
Correct answer: To ensure uniform adhesive transfer to the back of each plank
Back-rolling or troweling adhesive onto the back of planks in addition to the subfloor ensures full transfer and eliminates hollow spots beneath the finished floor.
Question 5: Which condition requires the installer to acclimate solid hardwood flooring for a longer period before installation?
- Flooring stored in a climate-controlled warehouse
- Flooring installed in a bathroom
- Flooring with a higher initial moisture content than the job site EMC (Correct answer)
- Flooring installed during summer months
Correct answer: Flooring with a higher initial moisture content than the job site EMC
When flooring arrives wetter than the job site equilibrium moisture content, extended acclimation is needed to allow the wood to dry down to match the environment.
Question 6: When using a moisture barrier membrane under laminate flooring on a concrete slab, the membrane laps at seams should overlap by a minimum of:
- 2 inches
- 6 inches
- 8 inches
- 12 inches (Correct answer)
Correct answer: 12 inches
Moisture barrier membranes on concrete should overlap at seams by at least 12 inches and be taped to prevent moisture migration between sheets.
Question 7: An inspector observes that the installer placed the laminate flooring with the long side of the planks perpendicular to the primary light source in a room with a large window. This is:
- A code violation
- Non-standard but acceptable
- The preferred installation direction (Correct answer)
- Required only for solid hardwood
Correct answer: The preferred installation direction
Running planks perpendicular to the primary light source is the industry-preferred direction as it minimizes the visual appearance of joints and enhances the floor's aesthetic.
WLFI Installation Standards & Techniques 3
When installing engineered hardwood over a concrete slab, which installation method is NOT typically recommended by manufacturers?