AHAmmax Home
Comparable selection

The closest house is not always the best comparison

A useful comparable set is built through several screens. Distance matters, but so do neighborhood boundaries, living area, property type, age, land, and differences that never appear in a spreadsheet.

Written and reviewed by Ammax Home Editorial · Updated August 23, 2026 · 10 min read

Begin with a broad, explainable search

A comparison process should be repeatable. Start with a defined radius, the same property class, a living-area range, and—when available—an age range. Ammax Home defaults to one-half mile, the same district property type, plus or minus 15 percent of published living area, and an optional plus or minus ten years built. These are starting screens, not universal appraisal rules.

The Texas Comptroller explains that the sales-comparison approach uses recently sold similar properties and adjusts them for differences. Public appraisal records do not always supply complete sale prices, so Ammax Home uses appraisal values for descriptive screening. It does not label an appraisal-value comparison as a sales-comparison appraisal.

Location is more than a radius

A radius is objective and easy to reproduce, but it can cross boundaries that buyers notice. A freeway, bayou, rail line, school attendance zone, municipal boundary, flood-control feature, commercial corridor, or subdivision entrance can separate two nearby houses. Conversely, a strong match just outside an arbitrary radius may belong to the same competitive market area.

Use the radius to produce candidates, then inspect the map and neighborhood context. Record why a property on the other side of a barrier was removed. If too few candidates remain, widen the radius gradually rather than changing every filter at once.

Living area controls scale—but verify the field

Larger and smaller homes often attract different buyers and can display different value-per-square-foot patterns. A plus or minus 15 percent screen keeps the comparison near the subject's scale while leaving room for normal variation. For a 2,000-square-foot subject, that range is 1,700 to 2,300 square feet.

Published living area may differ from a listing, survey, permit, or measurement standard. It may exclude or classify finished areas differently. If an account has multiple buildings, additions, or a garage conversion, read the building detail instead of relying only on the summary total. A precise calculation based on the wrong area is still misleading.

Match property type before refining age

Single-family detached houses should not be casually mixed with townhomes, duplexes, condominiums, vacant land, or commercial accounts. Even within a broad single-family code, differences such as one-story versus two-story design, attached versus detached structures, or materially different construction quality can affect utility and appraisal treatment.

Year built is a useful second screen because construction eras share design and material patterns. It is not a condition score. A renovated 1950s home may compete differently from an unrenovated neighbor built the same year. Use age to narrow the list, then examine condition, effective age, quality, and known renovations when reliable evidence exists.

Separate land from improvements

Two houses of similar size can sit on very different sites. Lot area, frontage, shape, corner influence, access, view, flood exposure, easements, and redevelopment potential can affect land value. Total market PSF assigns all land value to the building's square footage, so an expensive site can make an ordinary structure look costly per square foot.

Review the district's land allocation and improvement allocation separately. Improvement PSF can help identify whether the structure component is unusually high or low within the filtered set. It still does not measure renovation quality directly, and it should not be treated as construction cost.

Build a final set by explaining exclusions

A credible final set is not simply every result below a chosen PSF ceiling. For each candidate, ask whether it is similar enough in location, scale, class, age, site, and condition to inform the question. Write a short inclusion or exclusion note. Examples include “same subdivision and size; retained,” “backs to commercial use; review separately,” or “living area appears incomplete; excluded pending verification.”

A stronger habit

Change one screen at a time and keep an audit trail. That makes it possible to explain why the final group changed instead of selecting only properties that support a preferred result.

Common selection mistakes

  • Keeping only lower-valued properties without first applying the same physical criteria.
  • Mixing capped appraised value with uncapped market value.
  • Treating missing living area or year built as zero.
  • Ignoring neighborhood barriers because the straight-line distance is short.
  • Using one unusually renovated or distressed property as the center of the analysis.
  • Assuming a district's value proves a private sale price.

Official reference