If you are seeing gaps or exploded faces after attempting to round your edges, you are not alone. This issue is typically caused by a combination of SketchUp’s internal geometric limitations, unclean base topology, or incorrect plugin settings.

Reduce your Offset value in the plugin toolbar until the preview shows clean, green lines without red intersections. If you must have a large radius, you may need to simplify the surrounding geometry first. 3. Cleaning Up "Cracked" Top Faces

Plugins often crack the top face because they encounter "dirty" geometry. Ensure your top surface is perfectly flat and isolated before running any tools.

Often, the crack isn't a hole; it's a hidden edge or a reversed face. Zoom into the crack top.

Most users rely on (the industry standard). This plugin has three modes: Sharp , Round , and Bevel .

Before running the plugin, ensure the top face is a single, uninterrupted plane. Reveal hidden geometry by going to .

Always run Right-click → Reverse Faces on your object before using Round Corner. Ensure all exterior faces are white (front) . A mix of front/back faces is a guaranteed way to get cracks on top surfaces.

If the crack appears but the model is otherwise correct:

Fredo6 developed FredoCorner as a paid evolution of the tool. It is based on a different, more robust algorithm that handles complex triangulated shapes much better.

When rounding corners on surfaces that are not perfectly flat or perpendicular, the plugin may push vertices out of alignment. SketchUp cannot bridge these non-planar points with a single flat face, so it either leaves a hole or creates a web of messy triangles.

Let me know these details, and we can find the quickest way to get your model perfectly smooth. Share public link

To help you get this sorted out right away, could you tell me you are using, and whether this is a commercial extension like FredoCorner or the classic RoundCorner ?

The RoundCorner plugin (and native tools) relies on a continuous, "manifold" (watertight) mesh to calculate offsets. If the top of your surface consists of exploded, reversed, or non-manifold geometry, the plugin will fail to find a continuous path, resulting in cracked or hollow corners.