CFI Adhesives, Fasteners & Transition Systems 3 — Questions and Answers
Question 1: What is the purpose of 'back-buttering' large-format tiles during installation?
- To ensure full mortar coverage on the tile back and prevent hollow spots (Correct answer)
- To speed up adhesive curing
- To add color to the grout joint
- To roughen the tile surface for better adhesion
Correct answer: To ensure full mortar coverage on the tile back and prevent hollow spots
Back-buttering applies additional thin-set to the tile back to fill voids and ensure 95% or greater mortar contact required for large-format tiles.
Question 2: How long should most water-based flooring adhesives cure before allowing heavy rolling traffic on a commercial installation?
- 24–72 hours depending on manufacturer instructions (Correct answer)
- 1 hour
- 5 minutes
- 7 days minimum always
Correct answer: 24–72 hours depending on manufacturer instructions
Most water-based adhesives require 24–72 hours of cure time before heavy rolling loads are introduced to prevent adhesive shear failure.
Question 3: What type of fastener is used to attach wood flooring to a concrete subfloor without adhesive?
- Concrete screw or powder-actuated fastener (Correct answer)
- Ring-shank staple
- Cleat nail
- Standard wood screw
Correct answer: Concrete screw or powder-actuated fastener
Concrete screws (e.g., Tapcon) or powder-actuated fasteners (e.g., Ramset) are used to mechanically attach wood sleepers or nailer strips to concrete for a nail-down installation.
Question 4: When installing a floating floor, why must transition strips never be glued to the floating floor itself?
- Gluing restricts the floor's movement and can cause buckling or gaps (Correct answer)
- It would damage the adhesive in the transition
- Transitions are always nailed to joists
- Gluing is acceptable if the adhesive is flexible
Correct answer: Gluing restricts the floor's movement and can cause buckling or gaps
Floating floors must be free to expand and contract; gluing transitions to the floor prevents this movement and causes structural failure.
Question 5: Which type of transition piece is used where a floating floor meets a sliding door track?
- End cap or square-nose molding (Correct answer)
- T-molding
- Stair nose
- Reducer
Correct answer: End cap or square-nose molding
An end cap or square-nose molding terminates the flooring edge cleanly at a door track without needing to bridge to another floor surface.
Question 6: What is the risk of using too much adhesive when installing resilient sheet flooring?
- Adhesive bleeds through seams and prevents proper seam welding (Correct answer)
- The floor bonds too strongly
- Adhesive cures too fast
- It reduces subfloor moisture
Correct answer: Adhesive bleeds through seams and prevents proper seam welding
Excess adhesive can migrate to the seam area, contaminating the seam weld and preventing proper fusion, which leads to seam failure.
CFI Adhesives, Fasteners & Transition Systems 3
What is the purpose of 'back-buttering' large-format tiles during installation?