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Part of: GLA & Appraisal Standards: The Complete Guide

Appraisal Sketch Addendum: What It Must Contain and Why Reviewers Reject It

The sketch addendum is one of the most scrutinized parts of a residential appraisal. It's the only place in the report where your GLA calculation is fully visible, dimensions, shape, level-by-level breakdown, and total area. Getting it wrong is a fast path to revision requests and, in audit situations, USPAP issues.

What is a sketch addendum?

A sketch addendum is a scaled or diagrammatic drawing of a property's floor plan that accompanies the appraisal report. It shows the shape and dimensions of each level of the home, labels each area (GLA, garage, below-grade finished area, etc.), and provides the mathematical support for the total GLA figure reported on the URAR or other form.

The sketch is required, not optional, on conventional loan appraisals subject to UAD requirements. Fannie Mae, Freddie Mac, FHA, VA, and USDA all expect a sketch that supports the reported GLA. Reviewers who can't verify the GLA calculation from the sketch will kick the report back.

Required elements of a compliant sketch addendum

Element	Requirement	Common Rejection Cause
Exterior dimensions	Every wall labeled to nearest 0.5 ft; strings must add up	Dimension strings that don't reconcile across the sketch
Level-by-level breakdown	Each level shown separately; GLA and BGFA visually separated	Multiple levels combined; basement mixed into GLA
Area labels + subtotals	Each area labeled with type and sq ft (e.g., "First Floor GLA: 1,240 sq ft")	Unlabeled areas; totals that don't reconcile to form
Scale indicator	Stated ratio or graphic scale bar; drawn proportions must match labels	No scale; or dimensions inconsistent with drawing scale
Total GLA summary	Above-grade GLA total separate from BGFA; must match URAR	Sketch totals differ from appraisal form totals

The ANSI Z765-2021 standard and UAD requirements together define what a compliant sketch must include:

Exterior dimensions

Every wall segment must be dimensioned. ANSI requires exterior measurements to the nearest half-foot. Dimensions must be labeled on the sketch, not just implied by a scale bar. Reviewers check that the labeled dimensions add up correctly (e.g., two offset widths should sum to the total building width).

Level-by-level breakdown

Each level (main floor, upper floor, basement, etc.) must be shown separately with its own dimensions and area calculation. Combining multiple levels into a single drawing without labeling is a common reviewer complaint. Above-grade finished area and below-grade finished area must be visually and numerically separated.

Area labels and subtotals

Each area on the sketch must be labeled with its type and its computed area. Common labels include: "First Floor GLA: 1,240 sq ft," "Attached Garage: 420 sq ft," "Finished Basement: 680 sq ft." Reviewers need to see that the numbers are additive and reconcile to the totals on the appraisal form.

Scale indicator

The sketch must include a scale, either a stated ratio (1/4" = 1') or a graphic scale bar. The dimensions on the sketch must be visually consistent with the stated scale. A sketch where the labeled dimensions don't match the drawn proportions is an immediate red flag for reviewers and for appraisal management companies (AMCs) running automated QC.

Total GLA summary

The sketch addendum should state the total above-grade GLA (sum of all above-grade finished levels). Below-grade finished area is listed separately. The totals should match the figures reported on the URAR form, if they don't, the report will be flagged.

Common reasons appraisal sketches get rejected

Dimension strings don't add up

If the north wall is labeled as two segments of 18' and 24', the total for that side should be 42'. If the opposite wall is labeled as a single 40', there's a 2-foot discrepancy. AMC QC systems and lender reviewers check this automatically. Always verify your dimension strings before submitting.

GLA doesn't match the URAR

The total GLA on the sketch addendum must equal the GLA on the face of the appraisal form. A 10-square-foot rounding difference will be flagged. If you updated your field sketch and recalculated GLA after the initial draft, verify that the form was updated to match.

Missing level separation

A two-story home needs two separate level drawings. Stacking both floors on one sketch without clearly delineating levels, or showing only one level for a multi-story home, is a compliance failure. Some reviewers will also flag a single-level sketch that doesn't clearly indicate there is only one level.

Garage included in GLA total

The garage footprint must be shown on the sketch (it's part of the building perimeter), labeled as "Garage," and excluded from the GLA total. Sketches that show the garage area but roll it into the GLA number, even accidentally, create a significant compliance issue.

Non-conditioned space included

Covered porches, unheated sunrooms, and storage areas cannot be counted as GLA under ANSI Z765-2021. Show them on the sketch if they're within the roofline, but label them separately and exclude from GLA. Reviewers in AMC systems are trained to spot these.

Producing a sketch addendum from a floor plan

Most residential appraisers produce their sketch in the field using a dedicated tool — Apex Sketch, SketchMaster, or a similar product (see the EZ Sketch alternatives guide for browser-based options). These tools embed the sketch directly into the appraisal file. The field sketch and the report are one document.

But what if you have an existing to-scale floor plan? New construction, permit drawings, CubiCasa or Matterport outputs, or floor plans from a prior appraisal can all serve as the basis for a GLA calculation. The limitation is that most floor plan files don't produce a sketch in the format appraisal software expects.

The practical workflow: calculate GLA from the floor plan (using PlanSnapper or manual scaling), then re-enter the dimensions into your sketch software to produce the compliant addendum. You don't have to re-measure, you're just drafting the sketch to reflect the known dimensions. Many appraisers find this faster than pure field measurement for properties where good floor plans already exist.

Sketch from a PDF floor plan

PDF floor plans are common for new construction and permitted additions. They're to scale and include dimension callouts. If the callouts are visible, you can read the dimensions directly and enter them into your sketch software. If callouts are missing, PlanSnapper lets you set scale from any known dimension and derive the rest, giving you accurate wall lengths to enter.

Sketch addendum format requirements by lender

Fannie Mae and Freddie Mac accept any compliant sketch format embedded in the appraisal file. FHA appraisals on Form 1004 must include a sketch that shows the subject's dimensions and GLA calculation. VA and USDA have similar requirements aligned with UAD.

Some AMCs and lenders have additional requirements, minimum sketch resolution, specific labeling conventions, or a requirement that the sketch software name and version appear on the addendum. Check your lender client guidelines before submitting an unusual sketch format.

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Bottom line

The sketch addendum is your measurement documentation. Reviewers use it to verify GLA, check dimension consistency, and confirm that non-GLA areas are properly separated. Get the dimensions right, label every area, show each level separately, and make sure the totals reconcile. A clean sketch prevents revision cycles and demonstrates measurement competency.

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Frequently Asked Questions

What must an appraisal sketch addendum include?

An appraisal sketch must show all exterior dimensions with measurements, the perimeter layout of each level, identification of above-grade and below-grade areas, garage and other non-GLA structures, and a calculated area total for each section. Fannie Mae guidelines require the sketch to clearly separate GLA from non-GLA space.

Why do reviewers reject appraisal sketches?

Common rejection reasons include missing dimensions, non-closing perimeters (math doesn't add up), failure to separate above-grade and below-grade areas, unlabeled rooms, garages included in GLA, and sketches that don't match the appraiser's room count or GLA total on the form.

What software do appraisers use to draw sketches?

Common appraisal sketch software includes SketchUp, ACI Sketch, and built-in sketching tools in platforms like Total by a la mode, Anow, and ClickForms. PlanSnapper lets appraisers upload existing floor plans and trace them to produce accurate GLA calculations instantly.

Is a hand-drawn sketch acceptable on an appraisal?

Hand-drawn sketches are technically acceptable if they include all required dimensions and area calculations, but most lenders and AMCs prefer digital sketches that clearly show all measurements. UAD compliance generally favors digital sketches that can be reviewed electronically.

How is the sketch addendum different from the floor plan?

A floor plan shows the interior layout including room locations, doors, and walls. An appraisal sketch addendum focuses on exterior dimensions and area calculations. The sketch is designed to verify and support the GLA figure, not to show interior details. Both may appear in an appraisal package, but the sketch is the measurement tool.

Does the sketch addendum need to show the garage separately?

Yes. Garages must be shown as a separate structure on the sketch and are never included in GLA. The sketch should label the garage with its own dimension lines and area calculation. Appraisers report garage type and size in the improvements section of the appraisal form.

What happens if the sketch dimensions don't match the GLA on the form?

A discrepancy between sketch dimensions and the reported GLA on the form is an appraisal error that triggers review flags. The GLA on the form must match the sum of above-grade finished area shown on the sketch. Lenders and AMC reviewers often check this automatically.

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