What is the purpose of a threshold (sill) in tile installations and how should it be installed?

• A. Provides a transition between floor surfaces and helps water management; installed level with adjacent tile and sealed to prevent moisture intrusion.
• B. As decorative trim with no water considerations.
• C. To elevate doorway aesthetics; install with random height.
• D. Only for door clearance.

Answer: (A)

Thresholds in tile work serve as a transition between different floor surfaces and help manage moisture at doorways or wet areas. By bridging the height difference between rooms and directing water away from the seam, the threshold protects the subfloor and maintains a clean edge where tiles meet.

The best answer describes a threshold that creates a smooth transition and helps water management. Installing it level with the adjacent tile ensures a seamless, even surface that reduces trip hazards and prevents gaps that could trap moisture. Sealing the joint between the threshold and the tile with a flexible, water-rated sealant blocks moisture intrusion into the substrate and tile bed, supporting a long-lasting, watertight installation.