Are end-unit townhouses worth more than interior units of the same square footage?

Yes, typically. End units have more exterior walls, more windows, and more natural light, which buyers prefer. Appraisers develop a market-derived end-unit adjustment from paired sales of end vs. interior units in the same complex. The premium varies by market but is often 5-15% of the home's value. PlanSnapper helps verify that both unit types have accurately measured GLA before comparing them.

How is square footage measured differently in a townhouse vs. a detached home?

The measurement methodology is the same, exterior dimensions, above-grade only, ANSI Z765 compliant. The practical difference is that townhouses share party walls. ANSI Z765 specifies measuring to the center of shared walls (party walls) rather than to the interior or exterior of the shared wall. This is the standard approach for any attached dwelling, including condos and rowhomes.

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.

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Townhouse vs condo: why the difference matters

Factor	Fee-Simple Townhouse (PUD)	Condo
Ownership	Fee-simple (structure + land)	Airspace unit; common area ownership shared
Appraisal form	Form 1004 (or 1073 if legally condo)	Form 1073
Measurement method	Exterior dimensions, ANSI Z765	Interior dimensions, ANSI Z765 condo provisions
GLA calculation	Exterior perimeter per level	Interior wall-to-wall per level
Shared wall treatment	Measure to exterior face of party wall	Interior face of perimeter walls
Comparable selection	Similar townhouses in same PUD or market area	Same complex or similar condo projects

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 thedeed 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:

Measure the front and rear exterior faces of the unit (accessible sides).
Measure the depth of the unit from front to back at the exterior.
Use the floor plan, builder drawings or a professional scan, to get the full exterior width including shared wall thickness.
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:

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

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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, makingGLA 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.

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Frequently Asked Questions

How is square footage measured on a townhouse?

Townhouse GLA is measured the same way as detached homes, from the exterior above-grade finished heated space. However, exterior measurements may be complex when walls are shared with adjacent units. Appraisers measure from the exterior of the unit including shared party wall thicknesses.

Does shared wall thickness count toward townhouse square footage?

Typically, appraisers measure to the exterior of the unit structure, which includes the homeowner's portion of party walls. The exact convention can vary by appraiser, but consistency across comparables is what matters most for accurate GLA adjustments.

What counts as GLA in a multi-story townhouse?

Each above-grade story is measured separately and added together. Any levels that are partially below grade are excluded from GLA. A finished basement in a townhouse is reported as below-grade finished area, not GLA, the same rule as for detached homes.

How do townhouse appraisals differ from single-family home appraisals?

Townhouse appraisals use comparable townhouse sales, not detached single-family homes, to avoid comparison across fundamentally different product types. HOA fees, shared amenities, and party wall considerations are noted. GLA is calculated the same way, but the appraiser must adjust for any differences in garage configuration, end-unit vs. interior-unit location, and association dues.

Does a rooftop deck add to a townhouse appraisal?

A rooftop deck adds value as an outdoor amenity but does not count toward GLA. Appraisers make market-based adjustments for townhouses with rooftop decks compared to those without, using paired sales where available. In urban markets, rooftop decks can be a significant value driver.

How is GLA calculated on a three-story townhouse?

Each above-grade floor is measured separately and the totals are added together. Appraisers measure from exterior walls on each level. Finished basement space is excluded from GLA but noted separately. If the townhouse has a garage on the ground floor with living space above, only the above-grade finished floors count toward GLA.

Why do townhouse appraisals sometimes come in lower than expected?

Townhouses can be harder to appraise because good comparables, similar attached units in the same complex, may be limited. Appraisers must adjust for differences in end-unit vs. interior-unit location, floor plan layout, and view. GLA discrepancies between listed and actual square footage are also common in attached housing, which can suppress the appraisal value.