Is it possible to lock a dimension in Revit?
Short Answer
Yes, it is possible to lock a dimension in Revit by placing an aligned dimension and clicking the Lock control on that dimension. This is the most common professional method for keeping elements constrained to a fixed distance or alignment. Limitation: over-constraining a model can cause conflicts and failed updates.
What You Need to Know Before
Warning: Locking a dimension in Revit creates a constraint, not just a visual note. If the referenced elements are later edited, deleted, or made incompatible with the constraint, Revit can throw constraint errors or force unexpected geometry changes.
How to Lock a Dimension in Revit
Command: Aligned Dimension
Shortcut: DI
Quick Steps:
- On the Ribbon, go to Annotate tab > Dimension panel > Aligned.
- Pick the two references you want to control, then place the dimension.
- Click the small Lock icon that appears near the dimension value to constrain the elements.
Variables & Settings
Key Setting: Prefer: Witness lines / references on valid geometry
In Revit, the lock works only when the dimension is attached to valid references such as walls, reference planes, grids, or model element faces. If you dimension to weak or temporary references, the lock may fail or become unstable.
Why it Fails
Cause 1 (Geometry): The dimension is attached to references that cannot support a stable constraint, such as changing faces, temporary geometry, or incompatible element relationships.
Cause 2 (layers/Locks): The elements may be in a group, design option, linked model, or constrained by other existing locks, preventing a new dimension lock from being applied cleanly.
Cause 3 (Command/Logic): Too many constraints already exist, so adding another lock creates an over-constrained condition that Revit cannot solve.
Quick Fix & Best Practice
- Quick Fix: Delete the failing dimension lock, add a new Aligned Dimension between stable references like reference planes or core wall faces, then click Lock again.
- Manager’s Verdict: Use locked dimensions sparingly and only for design intent that must stay controlled. For flexible projects, reference planes and named constraints are usually safer than locking too many element-to-element dimensions.
FAQ
Can you unlock a locked dimension in Revit?
Yes, select the dimension and click the lock icon to toggle it off.
Is a locked dimension the same as an EQ constraint in Revit?
No, a locked dimension fixes a specific relationship, while EQ distributes spacing equally.
Can you lock dimensions in 3D views in Revit?
Not typically in the same annotation workflow; locked dimensions are most commonly created in plan, elevation, or section views.
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