How do you measure a log home for appraisal?

Log homes are measured using exterior dimensions under ANSI Z765, the same standard applied to conventional homes. However, log walls are typically 6 to 12 inches thick (or more for large round logs), which means the exterior square footage is notably larger than the interior living space. Appraisers measure from the exterior face of the logs, then use comparable sales with similar wall construction to ensure accurate adjustments. The thick walls are a feature of log construction and are not deducted from GLA.

FAQ · 5 min read

How to Measure a Log Home for Appraisal: GLA and Wall Thickness

Log homes are measured using exterior dimensions like any other residential property under ANSI Z765 -- but thick log walls create a real discrepancy between exterior square footage and interior living space. Here is how appraisers handle it correctly.

The wall thickness problem

A conventional home has 2x4 or 2x6 stud walls, typically 4 to 6 inches thick including insulation and drywall. Log homes are different. Depending on construction type, log walls range from:

Milled log (D-log, Swedish cope): 6 to 8 inches typical
Round hand-peeled logs: 10 to 14 inches typical
Large diameter full-round logs: 14 to 18+ inches
Timber frame with log siding: 6 to 10 inches

On a 40x50 foot home, 12-inch walls on all four sides reduce interior dimensions by 2 feet in each direction -- a difference of roughly 160 square feet between exterior GLA and actual interior living space. On larger log homes, this gap can exceed 400 square feet.

ANSI Z765: exterior measurement applies to log homes too

ANSI Z765-2021 requires measuring from the exterior faces of the exterior walls. This standard applies to all residential construction types, including log homes. Appraisers do not deduct wall thickness from the GLA calculation.

The reasoning: appraisers have always measured from the outside of the structure for consistency. Conventional homes also include wall thickness in their GLA -- it is just a much smaller number (6 inches vs. 12+ inches). Measuring all homes from the outside provides a consistent, verifiable standard.

The thick walls are a characteristic of log construction, not a deficiency. Buyers of log homes understand they are purchasing a structure where some square footage is wall mass rather than open floor space.

How to measure a log home accurately

The physical measurement process is the same as for any home:

Measure the exterior dimensions from the outer face of the logs (not from inside the corner notches or inset areas)
For round log corners, measure to the widest point of the log at the corner
Account for projections such as covered porches, bump-outs, or attached garage areas the same way you would on a conventional home
Measure each floor separately if the home is multi-story
Apply the same above-grade/below-grade rules under ANSI Z765 -- a walk-out basement in a log home is still below grade

Using a floor plan to measure a log home

Floor plans for log homes are often created by the builder or a 3D scanning service. If you have a floor plan from CubiCasa, Matterport, or an architect, you can use it to calculate GLA the same way as any other home -- by tracing the exterior perimeter, setting the scale from a known dimension, and letting the tool calculate area.

One important note: confirm whether the floor plan dimensions shown are exterior or interior. Builder floor plans for log homes sometimes show interior clear dimensions (the usable floor space inside the logs) rather than exterior dimensions. If the plan shows interior dimensions, the GLA you calculate will be smaller than the ANSI-standard exterior-measured GLA. Always verify with a field measurement or compare against the tax record.

Comparable sales adjustments for log homes

Because log home GLA includes substantial wall mass, appraisers need to use comparable sales of similar log construction when adjusting for size. Comparing a log home to a stick-built home on a per-square-foot basis will produce distorted adjustments -- the log home's GLA includes more non-usable wall space.

Best practice: find comps that are also log or heavy timber construction, or explicitly adjust for construction type differences. In markets with few log home sales, an appraiser may need to expand the search radius or use paired sales analysis to isolate the log construction premium and the wall-thickness-adjusted value difference.

Related resources

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