Learn · Real Estate Appraisal · 6 min read

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

Townhouse Square Footage Appraisal: How to Measure GLA on Attached Units

Townhouses sit in an awkward middle ground: they're attached like condos but owned like single-family homes. That distinction matters for how you measure square footage, which form you use, and how you select and adjust comparables.

Townhouse vs condo: why the difference matters

The key distinction is ownership structure, not physical layout. A townhouse (also called a PUD unit) is fee-simple ownership, the owner owns the structure and the land beneath it, subject to HOA covenants. A condo is ownership of airspace within a building, with common ownership of structure and land.

This distinction drives the appraisal form choice and the measurement methodology:

• Fee-simple townhouse: Use Form 1004 (URAR) or 1073 depending on how the project is legally structured. Measure using exterior dimensions per ANSI Z765-2021.
• Condo: Use Form 1073. Measure interior dimensions per ANSI Z765-2021 (interior to interior of perimeter walls).

Mistaking a fee-simple townhouse for a condo (or vice versa) leads to the wrong form, the wrong measurement methodology, and the wrong comparable set. Pull the deed and CC&Rs before you start.

How to measure townhouse GLA

For a fee-simple townhouse, ANSI Z765-2021 applies the same way it does to a detached single-family home: exterior dimensions, above grade, finished space only. The shared party walls don't change this. You measure to the exterior face of the wall, including through the shared wall to the centerline is not correct and not required.

In practice, measuring the exterior face of a shared party wall is physically impossible since the adjacent unit is in the way. The standard approach:

1. Measure the front and rear exterior faces of the unit (accessible sides).
2. Measure the depth of the unit from front to back at the exterior.
3. Use the floor plan, builder drawings or a professional scan, to get the full exterior width including shared wall thickness.
4. Calculate each level separately and sum above-grade finished area.

Floor plans are particularly valuable for townhouses because the shared wall measurement is embedded in the plan. A CubiCasa or iGUIDE scan of the unit captures interior dimensions; add the wall thickness (typically 6–8 inches per party wall) to get exterior figures. Or use builder permit drawings, which show exterior dimensions directly.

Multi-level layouts and the above-grade rule

Most townhouses are two or three stories. Each above-grade level is measured and summed. The rules:

Street-level with below-grade entry

Some townhouses, particularly urban rowhouses and "three-story" townhomes with garage entry at grade, have a lowest level that is partially or fully below grade. The below-grade portion, even if finished, does not count as GLA. Measure the grade line carefully. If the finished floor of the lowest level is at or below grade on any exterior wall, that level is below grade and excluded from GLA.

This frequently surprises owners and listing agents who count all three floors. A three-story townhouse where the ground level is garage-plus-rec-room below grade has two stories of GLA, not three.

Rooftop decks and upper-level terraces

Rooftop decks are not GLA, they're exterior space. Don't include them in your perimeter polygon regardless of how they're finished or how much the seller paid for them. Report them in Additional Features and make market-supported adjustments when comparables justify it.

Attached garage on the lowest level

A tandem or side-entry garage on the lowest level is not GLA even if it's finished with drywall and epoxy floors. Garages are excluded from GLA under ANSI regardless of finish. Measure and report the garage separately.

Using floor plans to measure townhouse GLA

Townhouse floor plans are common, builders almost always produce them, and many listing agents include them in the MLS. Working from a to-scale plan is often faster and more accurate than exterior measurements alone, especially in dense urban environments where access is limited.

With PlanSnapper, measure each level on its own polygon:

1. Upload the floor plan for the level you're measuring.
2. Trace the exterior perimeter of that level, excluding garage, unfinished storage, and below-grade areas.
3. Set scale from one known wall dimension, the front facade width from the builder spec sheet works well.
4. Record the result, then repeat for each above-grade level.
5. Sum the levels for total GLA.

Each polygon result stays independent, so you can report Level 1, Level 2, and Level 3 square footage separately in your sketch addendum before combining them into total GLA.

Comparable selection for townhouses

Fannie Mae requires comparable sales to be the same property type. For a fee-simple townhouse, your comparables should be other fee-simple townhouses or attached PUD units, not condos, not detached singles. If the market has limited attached sales, you can use detached comparables with appropriate comments and adjustments, but lead with attached comps whenever they're available within reasonable time and distance parameters.

GLA adjustments in townhouse markets can be tighter than in detached markets. Row units in the same development often have nearly identical floor plans, making GLA differences between comparables small. Your adjustments for location within the row (end unit vs interior unit), floor level, and exposure often carry more weight than GLA itself.

End units vs interior units

End units typically have an additional exterior wall, more windows, and often a side yard or additional outdoor space. They command a premium in most markets. If your subject is an end unit and your comps are interior units (or vice versa), you need a line-item adjustment. The market paired sales approach is the most defensible: find sales of end units and interior units within the same project and extract the premium directly.

Common errors on townhouse appraisals

• Using the wrong form. Condos need the 1073; fee-simple townhouses typically use the 1004. Check the legal structure before you commit to a form.
• Including below-grade finished space in GLA. Urban townhouses frequently have a below-grade level the owner calls "the first floor." If it's below grade, it's not GLA.
• Using interior dimensions instead of exterior. Fee-simple townhouses use exterior measurements. Interior dimensions (wall-to-wall) will understate GLA by the thickness of the exterior and party walls.
• Ignoring the HOA structure. Even though the townhouse is fee-simple, the HOA documents affect marketability and financing. Note the HOA, monthly dues, and any special assessments.
• Mixing attached and detached comparables without comment. If you must use detached comps, explain why and quantify the adjustment. Leaving it unexplained is a review flag.

Bottom line

Townhouse GLA measurement uses the same ANSI Z765-2021 exterior-dimension methodology as a detached single-family home. The complexity comes from shared walls (measure to the exterior face, use the floor plan), multi-level layouts (sum only above-grade finished levels), and form selection (confirm fee-simple vs condo ownership before you start).

Get the ownership structure right, measure each level from a reliable floor plan or field sketch, and select truly comparable attached sales. The rest is standard appraisal practice.

Related: Condo Square Footage · ANSI Z765-2021 Standard · Below-Grade Finished Area

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