The information in this article applies to:
Is it possible to create a room with a ceiling that follows the pitch of the roof?
A ceiling that follows the underside of the roof is sometimes referred to as a cathedral ceiling, and can be created by disabling the flat ceiling setting within a room specification dialog.
In Home Designer 2024 and newer versions, flat ceilings can also be removed by selecting a room and clicking on the Turn Off Ceiling edit tool.