GLA and Measurement Standards · 5 min read

Townhouse Square Footage: How Appraisers Measure Attached Units

Townhouses are multi-story attached units that require careful measurement. Shared party walls, below-grade entry levels, interior-access garages, and varying floor plates all create questions about what counts toward GLA. Here is how appraisers handle it.

Exterior measurement includes shared walls

Under ANSI Z765-2021, residential square footage is measured from the exterior face of exterior walls. For a townhouse, the shared walls between units are considered exterior walls of the unit being measured, even though there is living space on the other side.

This means you measure to the centerline of the shared party wall — or, in practice, to the exterior face of the shared wall as if the adjacent unit did not exist. The result is an exterior measurement that reflects the full footprint of the unit.

This is consistent with how attached condominiums are handled. Each unit is measured to include its share of shared structural walls.

Multi-story measurement: each floor counted separately

Townhouses are typically two or three stories. Under ANSI Z765, each qualifying above-grade level is measured separately, then the totals are added together for the total GLA.

Qualification requirements are the same as for any floor level:

• Finished to a habitable standard
• Ceiling height at or above 7 feet over at least 50% of the floor area
• Accessible from inside the unit (not through a garage or exterior-only entrance)
• Above grade — not below the exterior grade line on any wall
• Townhouse square footage appraisal guide
• GLA vs Total Square Footage: What Is the Difference?
• ANSI Z765 vs BOMA: Square Footage Standards Compared

The open-to-below area over two-story living rooms does not get double-counted. You measure the floor area of each level, not the ceiling area.

What the "grade" issue looks like in townhouses

Many townhouses, particularly in hilly areas or dense urban developments, have a ground-level floor that is below grade on the street side but above grade on the rear. This is the same issue as a walkout basement, and the same rules apply.

A level is above grade if all four walls are fully above the grade line. A level is below grade if any wall is at or below the grade line, even partially. Below-grade finished space is excluded from GLA under ANSI Z765 and must be reported separately, clearly labeled as below-grade finished area.

This is one of the most common errors in townhouse appraisals. An entry-level floor that appears to be a full living level can be partially or fully below grade depending on the site. Verify the grade on all four sides before including it in GLA.

Attached garages in townhouses

Attached garages are excluded from GLA regardless of how finished they are. A townhouse with a finished interior garage that has flooring, drywall, and HVAC still does not count that space as GLA.

If the garage has been converted to living space without a permit, the situation becomes an unpermitted addition question. Most appraisers exclude it from GLA and note it as a garage conversion of unknown permit status.

Reporting townhouse square footage in an appraisal

On the 1073 (Individual Condominium Unit Appraisal Report) or 1004 (Uniform Residential Appraisal Report) — depending on whether the townhouse is in a condo regime or is fee simple — the GLA line reflects only the above-grade finished area as described above.

Below-grade finished area is noted separately, typically in the basement section or addendum. Garage area, covered porches, and unfinished storage are also noted separately. The goal is to give a lender a clear picture of what they are financing — and why the GLA figure is what it is.

How PlanSnapper helps with townhouse measurement

Townhouses with floor plans available from the developer, building department, or a 3D scanning service are ideal candidates for PlanSnapper. Upload the floor plan for each level, trace the exterior perimeter (including shared walls), set your scale reference, and get the area for that floor. Repeat for each above-grade level and add the totals.

The multi-polygon feature is useful here too. If a floor level has an odd shape — an L-plan, a section over the garage, or a recessed terrace — you can trace multiple polygons for the same level and the tool totals them automatically.

This is faster than calculating individual room measurements and manually adding them up, and more accurate than estimating from a rough sketch.

Related reading

Above-grade vs. below-grade: the full explanation covers how to evaluate grade line in more detail. Walk-out basement GLA rules is directly relevant for townhouses with below-grade entry levels.