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How to check a SketchUp model for errors

Updated · by Myles B

To check a SketchUp model for errors, look at it in Monochrome face style to spot reversed faces, open Window › Model Info › Statistics to see what the file holds, and work through the Outliner for loose geometry, doubled copies and things on the wrong tag. SketchUp has no single “check model” button, so the check is a short routine, or an extension that runs it for you.

What counts as an error in SketchUp

Most problems don't stop SketchUp from working. They show up later: a render with black patches, a 3D print that fails, a LayOut sheet with something missing, or a file that takes a minute to open. The common ones are:

  • Faces facing the wrong way (the blue-grey back side showing).
  • Stray edges left over from drawing, and faces that won't fill in.
  • Groups or components doubled in place, which flicker and count twice.
  • Materials, components and tags nothing uses.
  • Loose geometry outside any group, and geometry on the wrong tag.
  • Things at the wrong size, often from a unit mix-up on import.

A manual check, step by step

  1. Turn on Monochrome. Choose View › Face Style › Monochrome. Front faces turn white and back faces blue-grey, so any blue-grey you see from outside is a reversed face. See fixing reversed faces.
  2. Show hidden geometry. Choose View › Hidden Geometry to see what is hidden but still in the file. Hidden things still load, save and slow the model.
  3. Read the statistics. Open Window › Model Info › Statistics. It lists edges, faces, groups and component instances. Very high face counts for a simple model point at heavy imported objects.
  4. Purge what nothing uses. In the same Statistics page, click Purge Unused. It removes components, materials, tags and styles that nothing in the model refers to.
  5. Walk the Outliner. Open the Outliner panel (from the Window menu) and look for groups called just “Group” or “Component#12”, groups wrapping a single group, and very deep nesting.
  6. Check tags. In the Tags panel, turn each tag off and on. If something you expect to hide stays visible, it is on the wrong tag, or only part of it carries the tag (its faces and edges but not its group, or the other way round).
  7. Check the size. Use the Tape Measure on a door, a chair or anything you know. A door 170 feet tall usually means millimetres were read as inches on import.

What to fix first

Fix what changes the result before you tidy. Reversed faces and doubled geometry affect renders, exports and prints. Wrong scale affects everything. Unused items and naming only affect file size and how easy the model is to work with, so they can wait until the end.

Save a copy before a big cleanup. Most fixes are one undo step, but some removals, such as deleting a style, can't be undone.

Is there a SketchUp model checker?

SketchUp itself has Purge Unused and, for solids, the Entity Info panel, which says when a group or component is a solid. Free extensions cover single jobs: CleanUp³ for cleanup, Solid Inspector² for holes in solids. Our comparison says what each one is good for.

How Lookover checks a model

Lookover covers most of this routine. Choose Extensions › Lookover › Review model and it lists what it finds, with a one-click fix where there's a clear answer.

A review has two parts. More than thirty deterministic checks run first, with no AI, so the same model always gets the same results: faces painted on the back, stray edges, geometry doubled in place, unused materials, tags and components, and more. Then an AI review looks at the model from several angles and measures things, to catch what a rule can't, such as a post that stops short of the deck.

A review only reads the model. Nothing changes until you click Fix it, and each fix is one undo step. Some findings have no fix because only you can decide, and one check (styles no scene uses) is report-only because SketchUp can't undo removing a style.

Questions

Does SketchUp have a built-in error checker?

Not one that checks the whole model. Purge Unused in Window › Model Info › Statistics removes unused items, and Entity Info tells you whether a selected group or component is a solid. The rest is a manual routine or an extension.

How often should I check a model?

Before you send it anywhere: to a client, to LayOut, to a printer or to a renderer. A quick check after importing someone else's model also saves surprises later.

Can a check break my model?

Looking can't. Fixes can, if they remove something you wanted, so save a copy first and use undo (Cmd+Z on macOS, Ctrl+Z on Windows) if a fix goes wrong.