By John Flanagan
Just as in AutoCAD, you can choose continuous or baseline dimensions. Once you select the aligned dimension tool, click the edit type button on the properties palette and select the Baseline option in the drop down menu for the dimension string type.
Fig 1: Dimension String Type
Next place the baseline dimension string as illustrated (select the walls in the order shown).
Fig 2: Select Wall Faces in the order shown
Move the cursor and click where you want the baseline dimension string placed.
Fig 3: Aligned Dimension String
Use the same approach when placing Baseline Dimensions in Revit Structure and Revit MEP.