The Auto Perimeter Finder Is Not Detecting My Floor Plan Correctly. What Do I Do?

When auto-detection misses the walls or traces the wrong boundary, there is almost always a fixable cause. Here are the most common problems and how to resolve each one.

Cause 1: Extra elements outside the walls

This is the most common reason for incorrect detection. Floor plan images from CubiCasa, Matterport, iGUIDE, and most appraisal software include level labels, dimension strings, deck outlines, scale bars, and other elements that sit outside the exterior wall boundary.

The auto perimeter finder looks for the largest enclosed polygon in the image. If a deck outline or floating dimension text extends beyond the exterior walls, it may trace that instead.

Fix: Open the image in any image editor and paint over anything sitting outside the exterior walls with white. Takes about 30 seconds. See the full guide: How to Prepare Your Floor Plan Before Uploading

Cause 2: Low contrast between walls and background

The detector needs the wall lines to stand out clearly from the background. If your floor plan has light gray walls on a light gray background, or the image is faded, detection will struggle.

Fix: Open the image in an editor and increase contrast. Most image editors have a simple contrast slider. Aim for dark wall lines on a clean white background. Even a small contrast boost often makes a big difference.

Cause 3: Floor plan is at an angle

If the floor plan was photographed at an angle or scanned slightly crooked, the detection algorithm may have difficulty identifying the walls correctly.

Fix: Rotate the image so the floor plan is straight. Most image editors have a rotate or straighten tool. The floor plan does not need to be perfectly aligned, but it should be close to level.

Cause 4: Very complex or irregular shape

Homes with highly irregular footprints, many bump-outs, or curved walls can sometimes result in an auto-detection that is mostly right but misses a few points.

Fix: After auto-detection runs, you can manually adjust the perimeter. Click and drag any perimeter point to move it to the correct position. Add or remove points as needed to match the actual wall outline.

Tips for best auto-detection results

Upload a high-resolution image (800px wide minimum, wider is better)
Remove all labels, dimensions, and outlines outside the exterior walls before uploading
Make sure the image is straight, not at an angle
Use a floor plan with high contrast (dark walls on white background)
Upload one level at a time, not all floors on one image