FAQ · 6 min read

How to Measure a Townhouse for Appraisal

Townhouses present a few unique challenges for appraisers: shared walls reduce the measurable perimeter, multiple floors require separate calculations, and lower levels are often partially or fully below grade. Here is a step-by-step approach.

1. Determine the property boundaries

A townhouse shares one or more walls with adjacent units. Your GLA measurement includes only the area within the subject unit — measured to the exterior face of exterior walls, and to the centerline of shared party walls. Check the survey or plat if there is any ambiguity about where the shared wall is.

Some townhouse developments are technically condominiums with a different legal structure — verify whether the subject is fee simple (owns land + structure) or a condo interest, as this affects how you frame the report and select comparables.

2. Measure each floor separately

Under ANSI Z765, exterior measurements are taken for each story. For a townhouse, walk the exterior of the unit (front and back) and note the footprint dimensions. For interior floors where the exterior is not accessible (middle floors of a rowhouse), measure interior dimensions and add wall thickness on the exterior walls.

Calculate finished area on each above-grade floor. A typical 3-story townhouse would have three separate floor area figures that are then summed for total GLA.

3. Assess the grade line on the lower level

Many townhouses have a ground-level entry or lower level that is partially or fully below the exterior grade at the front or rear. This is especially common in urban rowhouses and hillside townhouse communities.

Check the exterior grade on all sides of the lower level. If any side of the floor is below the adjacent exterior grade, that floor is below grade and must be excluded from GLA, regardless of how finished it is. Report it separately as finished below-grade area.

4. Exclude non-qualifying spaces

• Garage: Excluded from GLA even if it is an attached tuck-under garage on the lower level.
• Unfinished utility areas: HVAC closets, unfinished mechanical rooms — excluded.
• Covered but unenclosed areas: Covered patios, open decks — excluded.
• Ceiling height less than 7 feet: Any finished area under a 7-foot ceiling does not count toward GLA under ANSI Z765.

5. Calculate and cross-check

Sum the above-grade finished areas from each qualifying floor. Compare your total against MLS and county records as a reasonableness check — not to accept those numbers, but to flag large discrepancies worth investigating.

Document your grade-line reasoning in your workfile, especially for lower levels. If you are excluding a fully finished lower level as below-grade, that is a common point of contention with clients and reviewers — your notes should be clear.

Common mistakes to avoid

• Using MLS square footage without verifying: Agents frequently misreport townhouse GLA by including below-grade finished area or garage space.
• Measuring to shared wall face instead of centerline: Party wall measurement should be to the centerline, not the full exterior face (which belongs partly to the adjacent unit).
• Skipping below-grade documentation: Even if below-grade area does not count in GLA, it should be measured, reported, and considered in the analysis.
• Inconsistent comparable selection: Make sure your comps are also townhouses measured on the same basis. An attached townhouse measured at 1,400 sq ft is not directly comparable to a detached single-family measured at 1,400 sq ft without adjustment.