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Part of: Square Footage by Property Type: What Counts and What Doesn't

New Construction Square Footage Appraisal: How GLA Is Measured Before and After Completion

A new construction appraisal often happens before the home exists, or at least before it's finished. The appraiser calculates GLA from architect drawings, confirms the specifications, and delivers an "as proposed" value. Then there's a final inspection when construction completes to verify the property was built to plan. Here's how each stage works.

Types of new construction appraisals

Lenders require different appraisal forms and approaches depending on where the home is in the construction process:

As-proposed appraisal (Form 1004 with "proposed" condition)

The most common new construction appraisal. The appraiser inspects the lot (if construction has started) or reviews the site, analyzes the architect drawings and specifications, calculates GLA from the plans, selects comparable sales, and delivers a value based on the home as it will be when complete. The report is conditioned on construction being completed per the reviewed plans and specifications.

As-under-construction appraisal

When the home is framed but not finished, the appraiser inspects the construction progress and provides an updated value. This is sometimes required at draw stages for construction loans. GLA can be verified against the framing at this stage, though final finishes aren't yet visible.

Final inspection / completion certification

After construction is complete, most lenders require a final inspection, Form 1004D or a standalone completion certificate, confirming the property was built to plan. This is where discrepancies between the plans and the as-built home get caught. If the builder changed the floor plan during construction (a common occurrence), the appraiser documents the changes and re-evaluates the value conclusion if necessary.

How appraisers calculate GLA for new construction

Since the home isn't built yet (or isn't accessible), the appraiser calculates GLA from the architectural drawings provided by the builder. These drawings must be to scale and show the full exterior dimensions of each level.

The standard approach:

1. Obtain the site plan and floor plans for each level from the builder
2. Verify the plans are dimensioned and to scale
3. Calculate the exterior footprint of each above-grade finished level
4. Exclude the garage, any unfinished areas, and any non-conditioned spaces
5. Sum the above-grade GLA and document the calculation in the sketch addendum

The sketch addendum for a new construction appraisal often reproduces the relevant portions of the architect's drawing, annotated with the appraiser's dimension and area calculations. It's the same format as a field-measured sketch, it just derives dimensions from plan documents rather than a tape measure.

What happens if the plans don't have dimension callouts?

Architect drawings should include dimensions, but sometimes they're delivered without callouts, or the callouts are on a different sheet the builder didn't provide. In this case, the appraiser can scale from the drawing if a graphic scale or stated ratio is present. Many appraisers use digital tools (including PlanSnapper) to trace the exterior perimeter of the floor plan, set the scale from any known dimension or scale bar, and derive accurate GLA from the scaled drawing.

If no scale information is available at all, the appraiser should request complete dimensioned drawings from the builder before proceeding. An appraisal based on undimensioned plans with no scale reference is not defensible.

What plans and specifications must the builder provide?

For a Fannie Mae-eligible new construction appraisal, the builder typically must provide:

• Site plan, showing the lot, building footprint, setbacks, and any site improvements
• Floor plans, for each level, dimensioned and showing room layout
• Elevations, exterior views showing building height, roofline, and window/door placement
• Specifications, describing finishes, materials, appliances, and systems (HVAC, electrical, plumbing)

The specifications are critical because they define the quality level of the home. Two homes with identical GLA can have dramatically different values if one has standard-grade finishes and the other has custom cabinetry, hardwood throughout, and a high-end kitchen package. The appraiser's comparable selection and adjustments should reflect the spec level, not just the size.

GLA discrepancies between plans and as-built

Builders frequently make changes during construction. A wall gets moved, a room gets enlarged, a covered porch becomes conditioned space, or the garage gets extended. These changes almost never get communicated to the appraiser who did the original appraisal.

The final inspection resolves this. The appraiser measures the completed home (or reviews updated plans) and verifies that the as-built GLA matches the appraisal. If the as-built is smaller than the approved plan, the lender needs to know, this could affect value and loan eligibility. If it's larger, the value conclusion may need to be updated.

Common causes of plan-vs-as-built GLA discrepancies:

• Builder substituted a smaller lot, which required a narrower footprint
• Owner upgrade added a covered patio that was converted to conditioned sunroom
• Permit amendment required a setback change that reduced a room
• Bonus room or unfinished third floor was finished as a change order
• Garage was expanded at the buyer's request, shifting the main living space slightly

Comparable selection for new construction appraisals

New construction comparables are the same as any other, similar GLA, location, age, quality, and condition. The challenge is that "new construction" is itself a quality differential. Buyers pay a premium for a new home, and the appraiser's comparable selection should reflect that.

When recent new construction sales exist in the market, use them. If the only available comparables are resales, apply a market-supported condition adjustment to account for the difference between new and resale homes. Document how you derived that adjustment, paired sales comparing new construction to recent resales of similar spec are ideal.

GLA adjustments for new construction use the same methodology as any other residential appraisal. Derive the price-per-square-foot adjustment from paired sales within the same market and quality tier. New construction GLA adjustments may differ from resale adjustments in the same market, especially at higher price points where the marginal value of additional space can vary significantly.

Using builder plans vs. getting a third-party floor plan

For the original appraisal, builder-provided plans are the standard. For the final inspection, especially when changes have occurred, some appraisers commission a third-party floor plan scan (CubiCasa, iGUIDE, or a professional measuring service) to get an independent as-built measurement. This eliminates reliance on updated builder drawings and provides a verifiable record of actual dimensions.

For production builders with standardized floor plans, the as-built typically matches the plan closely. For custom homes, the final inspection is more important, and a third-party floor plan provides cleaner documentation.

Bottom line

New construction appraisals calculate GLA from plans rather than field measurement, which makes the quality of the builder's drawings critical. Get dimensioned, to-scale plans before you start. Calculate GLA using the same ANSI Z765 exterior method you'd use on a completed home. Document the calculation in your sketch addendum. Then verify at final inspection that the as-built matches the plan.

The as-proposed GLA and the as-built GLA should agree. When they don't, the discrepancy needs to be documented and the value conclusion revisited if the change is material.

Related: Appraisal Sketch Addendum · Square Footage from PDF Floor Plans · Fannie Mae Square Footage Requirements

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