CHANGE WHERE MEASURED IN PLAN
It is possible to tell Revit where to measure the area of rooms bounded by walls.
For example you can have the area measured at face of walls or centre of walls.
NOTE:
The setting is global so effects all rooms in all views.
It applies to ALL walls, including external and curtain walls.
If you change the setting during a project areas of rooms will change from what they previously were.
To change the settings start from Home tab, Room & Area panel, select the black triangle,
then pick Area and Volume Computations.
Then make changes:
CHANGE WHICH HEIGHT ROOM IS MEASURED AT
By default the area of a room is measured at the level of the room is on. You can add an offset from the host level so the room is measured above the level.
This can be useful if you have upstands modelled as elements that are not room bounding.
The height room areas are measured at is a property of Levels.
Select a Level, and change the value of Computation Height.
You can change multiple levels by selecting all of the levels you want changed and editing Computation Height.
For greater flexibility assign a Global Parameter to Computation Height. Then only that global parameter needs to be changed to change all Levels.
First create the Global Parameter. Under Manage > Global Parameters.
Create a New global parameter, give it a sensible name, and a tooltip describing what it does.
Then give the Global Parameter a value.
Now go back and select all the Levels you want to change.
Pick the button to right of the Computation Height parameter,
and select the Global Parameter you created.
All the selected Levels will now have the Global Parameter value.