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Part of: GLA & Appraisal Standards: The Complete Guide

Appraisal Sketch Requirements: What Fannie Mae and FHA Require

The property sketch is one of the most scrutinized parts of an appraisal report. Underwriters check it against the GLA figure, the photos, and the comp data. Here's what it must show, and what missing or incorrect sketch elements look like to a reviewer.

Requirement	Fannie Mae (UAD)	FHA (HUD 4000.1)
Exterior dimensions on sketch	✅ Required	✅ Required
Each level shown separately	✅ Required	✅ Required
Area calculations per level	✅ Required	✅ Required
GLA labeled separately from below-grade	✅ Required	✅ Required
Garage dimensions included	✅ Required	✅ Required
Dimensions must close (balance)	✅ Required	⚠️ Not explicit — best practice
Reconcile with public records if different	⚠️ Comment required	✅ Explanation required
North arrow / orientation	⚠️ Common practice	⚠️ Common practice

Why the sketch matters

The sketch serves three functions in an appraisal report. First, it documents the methodology behind the GLA figure, reviewers can trace how every square foot was calculated. Second, it provides a spatial representation of the improvements that photos alone can't convey. Third, it's a verification tool: if the sketch dimensions don't add up to the reported GLA, something is wrong.

Fannie Mae, FHA, and most other lenders require a sketch in residential appraisal reports. An appraisal submitted without a sketch, or with a sketch that doesn't support the GLA figure, will be returned for correction.

What Fannie Mae requires in the sketch

Fannie Mae's Selling Guide and its UAD (Uniform Appraisal Dataset) specifications require the following in the appraisal sketch:

Exterior dimensions of each level of the dwelling, with individual dimensions labeled on each wall segment.
All levels shown separately, first floor, second floor, basement, etc., each with its own labeled perimeter.
Area calculations shown for each level, with GLA and non-GLA areas (basement, garage) calculated and labeled separately.
Total GLA clearly identified, matching the GLA figure reported on the appraisal form.
Garage, carport, or other non-GLA structures shown with their own dimensions and area calculations.
North arrow or orientation indicator, technically required by some appraisal software guidelines, commonly included as standard practice.

Fannie Mae's guidelines also require that sketch dimensions close, meaning the labeled dimensions on a wall-by-wall basis must sum to the total exterior dimension. If opposite walls don't balance, the sketch has an error.

What FHA requires

FHA (HUD Handbook 4000.1) requirements align closely with Fannie Mae's. The appraiser must include a sketch of the property that shows:

The perimeter of the property improvements with dimensions
Calculated GLA for above-grade areas
Calculated area for below-grade areas (shown separately from GLA)
Garage and other non-living structures shown with dimensions

FHA additionally requires the appraiser to reconcile the sketch GLA with any county records or other sources cited in the appraisal. If the sketch shows different square footage than the county assessor record, the appraiser must explain the discrepancy.

ANSI Z765-2021 and the sketch

ANSI Z765-2021 doesn't prescribe a specific sketch format, but its measurement methodology implies what the sketch should capture. Since ANSI requires exterior dimensions rounded to the nearest half-foot, the sketch dimensions should reflectexterior measurements, not interior measurements, not approximations.

ANSI also requires that different areas be reported separately: above-grade GLA, below-grade finished area, and garage or non-living structures. A sketch that rolls all of these into a single number without separation doesn't support ANSI-compliant GLA reporting.

Level-by-level breakdown

Above-grade levels

Each above-grade level gets its own sketch. For a two-story home, that means a first-floor sketch and a second-floor sketch, each with labeled exterior dimensions and a calculated area. If the second floor has a smaller footprint than the first (a partial second story), the second-floor sketch shows only the finished above-grade perimeter of that level.

Below-grade levels

Basements and below-grade rooms are sketched separately with their own dimensions and area calculation. The below-grade finished area (BGFA) is labeled distinctly from GLA and must not be included in the GLA total. Reviewers specifically look for this, including basement square footage in GLA is one of the most common sketch errors flagged in appraisal review.

Garages and accessory structures

Attached garages are typically shown as part of the first-floor sketch footprint but with their area calculated separately and explicitly excluded from GLA. Detached garages, ADUs, and other accessory structures may be shown on the same sketch page or a separate sketch, but their areas must be labeled and not included in the main dwelling GLA.

Sketch software and digital sketches

Most appraisers use software to produce the sketch: SketchItUp, TOTAL Sketch (a la mode), ACI Sketch, or integrated sketch tools within their appraisal form software. These tools generate sketches with labeled dimensions and automatic area calculations.

The software handles the formatting, but the input is still the appraiser's field measurements. Errors in the field produce errors in the sketch regardless of the software used. If you measured a wall at 24 feet when it's actually 28 feet, the software will faithfully produce an incorrect sketch. For a complete walkthrough of the field measurement process, see how to measure square footage for a real estate appraisal.

When working from a professional floor plan (CubiCasa, Matterport, iGUIDE, or builder drawings), PlanSnapper gives you accurate exterior dimensions and area calculations that you can then transfer into your sketch software. Use the floor plan measurement as a cross-check on your field sketch, discrepancies between the two often surface measurement errors before they end up in the report.

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Common sketch errors that trigger underwriter flags

Dimensions that don't close. If the labeled wall segments on one side of the house don't sum to the same total as the opposite side, there's an error. Underwriters and automated systems catch this immediately.
Basement area included in GLA. The most common error in walk-out basement properties. The below-grade portion, even if fully finished, must be separated from GLA.
Missing levels. A two-story home with only a first-floor sketch. An attic conversion with no sketch. Any finished above-grade level without a corresponding sketch.
Sketch GLA doesn't match form GLA. If the sketch calculations sum to 1,842 sq ft but the form reports 1,960 sq ft, something is wrong, either the sketch is missing an area or the form has a typo.
Garage included in GLA total. A common error when the garage is attached and the sketch software includes it in the auto-sum if areas aren't labeled correctly.
Round numbers on every dimension. All walls being exact round numbers (20 ft, 30 ft, 40 ft) suggests the appraiser estimated rather than measured. ANSI requires measurement to the nearest half-foot, some walls should be 22.5 ft, 17 ft, 31.5 ft.

What a clean sketch looks like

A well-prepared sketch has labeled dimensions on every wall segment, a running total that closes (opposing sides sum to the same figure), clearly labeled areas for each level with GLA and non-GLA separated, and a final GLA figure that matches the appraisal form exactly.

It doesn't need to be architectural-grade. It needs to be accurate, labeled, and internally consistent. An appraiser who produces clean, consistent sketches builds a reputation with underwriters that translates directly into fewer stips and faster closings.

Bottom line

The sketch is the proof behind the GLA number. Fannie Mae and FHA requirements are clear: exterior dimensions, level-by-level breakdown, GLA and non-GLA separated, totals that close. Meet those requirements and you'll rarely hear back from underwriting about square footage.

The measurement process, not the software, is where accuracy is won or lost. Field measurements, floor plan cross-checks, and careful dimension verification are what keep the sketch clean. The software just draws what you give it.

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Related Resources

Official Sources

Fannie Mae Selling Guide: Improvements Section — Fannie Mae requirements for appraisal sketches including perimeter, dimensions, and GLA.

Frequently Asked Questions

What are Fannie Mae's requirements for appraisal sketches?

Fannie Mae requires a floor plan sketch showing the exterior dimensions of all above-grade living areas. The sketch must support the reported GLA and include all stories. Since 2022, Fannie Mae also accepts UAD 3.6 data submissions that include digital floor plan data.

Does every appraisal need a sketch?

For residential appraisals on properties securing Fannie Mae or Freddie Mac loans, yes, a sketch is required. Desktop and hybrid appraisals may use third-party measurement data, but the GLA must still be supported by dimensioned floor plan information.

What happens if the appraisal sketch is inaccurate?

An inaccurate sketch can result in an incorrect GLA, which affects the appraised value and comparable adjustments. Lenders may request a field review or reconsideration of value. Repeated sketch errors can be flagged in UCDP for pattern review.

What information must an appraisal sketch include?

A compliant appraisal sketch must show exterior dimensions on each wall segment, all levels drawn separately, area calculations per level, GLA clearly labeled and separated from below-grade and garage areas, and a total GLA that matches the figure reported on the appraisal form.

How does the appraisal sketch relate to the GLA figure on the appraisal form?

The sketch is the documentation trail behind the GLA number. The area calculations shown on the sketch must sum to the exact GLA reported on the appraisal form. If the two figures do not match, the report has an error that underwriters will flag for correction.

Can a digital or computer-generated sketch meet appraisal requirements?

Yes. Most appraisers use sketch software such as TOTAL Sketch, Apex Sketch, or ACI Sketch to produce digital sketches. These tools generate labeled dimensions and automatic area calculations. The software output satisfies Fannie Mae and FHA requirements as long as the dimensions entered reflect actual field measurements.

How do appraisers sketch multi-level homes?

Each level gets its own separate sketch with labeled exterior dimensions and a calculated area. A two-story home requires a first-floor sketch and a second-floor sketch, each showing the perimeter of that level. Below-grade levels are sketched separately and their area is clearly excluded from the GLA total.

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