What is a Revit ʼRoof by Footprintʼ vs. ʼRoof by Extrusionʼ?
Short Answer
In Autodesk Revit, Roof by Footprint is the most common method for creating roofs from walls or closed sketch lines in plan view, while Roof by Extrusion creates a roof profile from a side view and pushes it through a depth. Footprint is usually faster for standard building roofs. Limitation: extrusion roofs are less intuitive for plan-based edits.
What You Need to Know Before
Warning: Roof creation can fail if your sketch lines are not a closed loop or if the roof is created in the wrong view type. A very common mistake is using Roof by Extrusion for a roof shape that should be controlled by slope-defining boundary lines in plan.
How to Create a revit roof by Footprint or Roof by Extrusion
Command: Roof by Footprint / Roof by Extrusion
Shortcut: No default keyboard shortcut
Quick Steps:
- Go to Architecture tab > Build panel > Roof and choose Roof by Footprint for standard roofs or Roof by Extrusion for profile-based roofs.
- For Roof by Footprint, sketch or pick walls in a plan view, then use the Defines Slope checkbox on selected boundary lines in the Options Bar or Properties.
- For Roof by Extrusion, open an elevation or section, sketch the roof profile, set the Extrusion Start and Extrusion End values, then click Finish Edit Mode.
Variables & Settings
Key Setting: Defines Slope
Expert Setting: In Roof by Footprint, this option controls which sketch edges generate roof slope. Turning it off on selected lines is essential for creating gable edges, while leaving it on all edges typically creates a hip roof.
Why it Fails
Cause 1 (Geometry): The footprint or profile sketch is open, self-intersecting, or drawn in the wrong plane, so Revit cannot generate valid roof geometry.
Cause 2 (layers/Locks): Picked walls may be constrained, misaligned, or attached in ways that cause the roof boundary or overhang behavior to produce unexpected results.
Cause 3 (Command/Logic): Roof by Extrusion is used for a plan-driven roof, or Roof by Footprint is used for a shape better controlled from an elevation profile, causing difficult edits and inaccurate geometry.
Quick Fix & Best Practice
Quick Fix: Edit the roof sketch with Edit Footprint or Edit Extrusion, verify the sketch is closed, and check the Defines Slope setting on each boundary line.
Manager’s Verdict: Use Roof by Footprint for most architectural roof layouts tied to walls and plan geometry. Use Roof by Extrusion only when the roof shape is driven by a side profile, such as barrel, shed, or custom fascia-driven forms.
FAQ
Is Roof by Footprint better for residential roofs?
Yes, it is usually the fastest and most common method for typical residential roof plans.
Can Roof by Extrusion create curved roof profiles?
Yes, it is commonly used when the roof shape is defined by a custom or curved profile.
Can I change a footprint roof into an extrusion roof later?
No, you typically need to recreate it using the other roof creation method.
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