Core terms · definition
A rigid cement-based panel used as a stable, water-durable substrate for tile in wet areas — preferred over drywall behind tile in showers and on counters.
Source: Ceramic Tile Education Foundation — Guide to Underlayment for Tile
Where this term lands on a Columbus budget
The cost pages carry the current local ranges, and the guides explain what moves them. A published range becomes a project number only after someone looks at the site.