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How to Measure Square Footage from an Appraisal Sketch

Appraisal sketches are to-scale floor plan drawings with labeled wall dimensions. Whether the sketch came from Apex Sketch, WinTOTAL, ACI, or a scanned paper form, you can verify GLA from it in under two minutes by uploading to MeasureFloorPlan.com and tracing the exterior perimeter.

What is an appraisal sketch?

An appraisal sketch is a to-scale floor plan drawn by a licensed appraiser to document the layout and dimensions of a property. It shows the exterior perimeter, room shapes, and labeled wall measurements used to calculate Gross Living Area (GLA) for the appraisal report.

Most residential appraisers in the US use Apex Sketch (Bradford Technologies), WinTOTAL (a la mode), or ACI Sketch to produce these drawings. Each program exports the sketch as a PNG or PDF image with dimensions labeled on every wall segment.

Why verify GLA from the sketch?

Fannie Mae and Freddie Mac require ANSI Z765-2021 compliant GLA measurement on all conventional appraisals since March 2023. Errors in the original sketch — misclicks, transposed digits, missing areas — can produce incorrect GLA that affects value conclusions and loan decisions.

Tracing the exported sketch in a second tool takes two minutes and catches calculation errors before the report is submitted. It is also useful for reviewers, AMCs, and lenders who receive a sketch and want to independently verify the reported GLA.

How to export an appraisal sketch for measurement

The export process varies slightly by software:

Apex Sketch

1. Open the sketch and go to File, then Export.
2. Select PNG or PDF. Choose the highest resolution available.
3. Save to your desktop.

WinTOTAL (a la mode)

1. Open the sketch tab in your form.
2. Right-click the sketch and select Save as Image, or use File, then Print to PDF.
3. A full-screen screenshot also works if export options are limited.

Scanned paper sketches

Scan at 300 DPI minimum. Make sure the entire sketch fits in the frame with no cropped edges. A phone photo works if the sketch is flat, well-lit, and all wall labels are readable.

How to measure GLA from the sketch

1. Upload the sketch to MeasureFloorPlan.com. The tool accepts JPG, PNG, and PDF.
2. Trace the exterior perimeter of the above-grade living area. Click each exterior corner in sequence, following the same logic ANSI Z765 requires: above grade, finished, heated and cooled. Exclude the garage, basement, and any unfinished areas.
3. Set scale using one labeled wall dimension from the sketch. Click the two endpoints of that wall, then enter the labeled measurement. Pick the longest clearly-labeled dimension for best accuracy.
4. Read the result. The tool shows square footage for each polygon and a running total. For a two-story home, trace each floor separately and the total updates automatically.

What to do if the numbers don't match

A difference of 1-2% between the sketching software's GLA and MeasureFloorPlan.com is normal and attributable to rounding in wall dimensions. A difference larger than 2% is worth investigating.

Common sources of discrepancy:

• Missing area: A bump-out, bay window, or room was traced in the original sketch but not included in the GLA calculation. Check that your polygon covers the full perimeter.
• Included non-GLA area: The original sketch may have included a garage or basement in the GLA total. Retrace excluding those areas.
• Scale error: If the scale reference dimension was entered incorrectly in the original sketch, the entire calculation is off. Try setting scale from a different labeled wall to cross-check.
• Low-resolution scan: If the sketch was photographed at an angle or low resolution, corner detection errors accumulate. Rescan or take a flatter photo.

ANSI Z765 compliance notes

ANSI Z765-2021 requires that GLA be measured to the nearest square foot and include only above-grade, finished, heated and cooled space. The methodology used by MeasureFloorPlan.com — tracing the exterior perimeter and excluding non-qualifying areas — is consistent with ANSI Z765 requirements.

For multi-level homes, each floor is measured separately. Stairwells count on the floor where the stairs originate. Finished attic space above the knee wall counts if it meets the ceiling height requirement (at least 7 feet for more than 50% of the floor area).

Related guides

• Apex Sketch export and measurement walkthrough
• ANSI Z765 measurement guide
• Floor plan measurement for real estate appraisals
• GLA vs total square footage