Describe the function of a 'crack isolation membrane' under ceramic tile in interior floors.

• A. Increases moisture
• B. It isolates tile from substrate cracks
• C. Strengthens tile adhesion
• D. Acts as decorative layer

Answer: (B)

Crack isolation membranes are placed between the substrate and the tile to decouple movement. They provide a flexible interlayer that absorbs and disperses substrate movement, so cracks or shifts in the substrate don’t transfer to the ceramic tile above. In interior floors, this prevents hairline cracks in the substrate from showing up as cracks in the tile or causing tile failure, keeping the tile surface durable even when the substrate moves slightly. This is why the function is to isolate tile from substrate cracks. It doesn’t purposefully increase moisture, isn’t primarily for strengthening adhesion, and isn’t a decorative layer (though some products may offer waterproofing benefits).