CFI Adhesive & Underlayment Selection 2 — Questions and Answers
Question 1: Which adhesive type is most appropriate for installing vinyl composition tile (VCT) over a porous concrete subfloor?
- Epoxy adhesive
- Pressure-sensitive acrylic adhesive (Correct answer)
- Solvent-based contact cement
- Urethane wood flooring adhesive
Correct answer: Pressure-sensitive acrylic adhesive
Pressure-sensitive acrylic adhesives are the standard choice for VCT over porous concrete, providing proper bond without releasing VOCs associated with solvent-based products.
Question 2: When installing underlayment in a bathroom, which property is most critical for selection?
- High compressive strength only
- Moisture resistance (Correct answer)
- Maximum thickness for cushioning
- Thermal conductivity
Correct answer: Moisture resistance
Moisture resistance is the most critical property for bathroom underlayment because high humidity and potential water exposure can degrade non-resistant materials and damage the flooring.
Question 3: A flooring installer is working in a room with radiant heat. Which underlayment should be avoided?
- Cork underlayment
- Thin foam underlayment
- Thick foam underlayment over 3mm (Correct answer)
- Rubber underlayment
Correct answer: Thick foam underlayment over 3mm
Thick foam underlayment (over 3mm) acts as insulation and reduces heat transfer efficiency from radiant heating systems, potentially causing system malfunction or flooring damage.
Question 4: What is the primary function of a crack isolation membrane used under tile installations?
- To add thermal insulation under the tile
- To prevent substrate cracks from telegraphing through to the tile surface (Correct answer)
- To increase the overall height of the floor system
- To provide waterproofing for the tile surface
Correct answer: To prevent substrate cracks from telegraphing through to the tile surface
Crack isolation membranes are designed to absorb movement from substrate cracks so those cracks do not transfer stress up through the tile and grout.
Question 5: Which adhesive characteristic is described by 'open time'?
- The time until the adhesive fully cures and reaches maximum bond strength
- The period after spreading during which the adhesive remains workable and can bond materials (Correct answer)
- The shelf life of the adhesive before it is opened
- The time required for the adhesive to dry before foot traffic is allowed
Correct answer: The period after spreading during which the adhesive remains workable and can bond materials
Open time refers to the window after the adhesive is troweled onto the substrate during which it can still form an effective bond when flooring material is pressed into it.
Question 6: An installer must bond hardwood flooring over a concrete slab on grade. Which adhesive system is most appropriate?
- Water-based acrylic adhesive
- Pressure-sensitive adhesive
- Moisture-cured urethane adhesive (Correct answer)
- Latex-modified thin-set mortar
Correct answer: Moisture-cured urethane adhesive
Moisture-cured urethane adhesive is engineered for wood-to-concrete applications because it tolerates minor moisture vapor emissions and provides a flexible, strong bond that accommodates wood movement.
Question 7: Which underlayment type provides the best sound reduction for an upper-floor laminate installation?
- 6-mil poly sheeting
- Rosin paper
- Combination foam/film with IIC rating of 65 or higher (Correct answer)
- 1/4-inch lauan plywood
Correct answer: Combination foam/film with IIC rating of 65 or higher
Underlayment with a high IIC (Impact Insulation Class) rating, typically foam-based products rated 65 or higher, provides the best impact sound reduction in multi-story applications.
CFI Adhesive & Underlayment Selection 2
Which adhesive type is most appropriate for installing vinyl composition tile (VCT) over a porous concrete subfloor?