A custom home has no tract twin, no house of the same plan down the street that sold recently, so the appraiser cannot lean on a model-to-model match. Instead, construction quality is rated on the standardized quality scale from what the inspection shows and what the plans and builder records document, and each comparable is rated on the same scale. Comparables are then chosen for similar quality, size, lot and setting, often from a wider area, and every quality adjustment has to reflect how buyers in closed sales actually reacted.
This article is part of the Hillside, Custom and Luxury Homes series. The pillar, appraising a one-off house, covers the wider method; this one stays with construction quality on the San Bernardino County side of the coverage area.
What a tract twin gives, and what a custom home lacks
In Rancho Cucamonga's planned villages, such as Victoria and Terra Vista, lot sizes and floor plans repeat. A house there is compared with sales from the same builder's plan series, and the differences come down to condition, upgrades, lot and the date of sale. The error a reviewer looks for is a model from a different plan series used with no size or quality adjustment.
Up the slope the pattern breaks. Alta Loma and Etiwanda, the older foothill communities, hold custom homes with views across the valley beside older ranch homes on large lots. In Upland, the land rises north of the 210 to larger lots and view homes, and above the city limits San Antonio Heights is a community San Bernardino County describes as having "large lots, unique homes, and quiet streets." Houses in these places were often built one at a time, by different builders, on lots that differ in grade and view. The nearest sale may be a planned-village house a few minutes away that shares almost nothing with the subject. The Rancho Cucamonga and Alta Loma area page describes these two markets inside one city.
How construction quality is rated
A quality rating, the standardized grade from Q1 to Q6 describing the design, materials and workmanship of a house, is assigned to the subject and to every comparable. Fannie Mae's Selling Guide describes the top of the scale this way: a Q1 dwelling is "individually designed by an architect for a specified user," a Q2 dwelling is "often custom designed for construction on an individual property owner's site," and a Q3 dwelling is built "from individual or readily available designer plans." The Guide adds that "the selected rating must reflect a holistic view of the quality of construction," so one premium room does not lift the rating of an ordinary house.
The redesigned Uniform Residential Appraisal Report, mandatory for reports submitted to Fannie Mae and Freddie Mac on or after November 2, 2026, keeps the same scale. Freddie Mac's UAD 3.6 FAQ says it "has not changed, but definitions were rewritten to provide clarity." The rating is the appraiser's judgment from the inspection, written down so a reviewer can test it against the photographs and the description. The article on how condition and quality ratings are reported explains both scales.
What the owner can provide
Much of what sets a custom house apart is visible: the materials, the finish carpentry, the windows, the roof, the way the house sits on its lot. Some of it is not, and documents fill the gap. These help:
- Architect or builder information and plans, if available
- Any geotechnical, retaining wall or grading reports
- Permits, plans or a survey for any addition, remodel or ADU
- A list of improvements with approximate dates
The documents describe the house. They do not set its value, and a construction budget is not a comparable sale.
Finding comparables without a twin
Fannie Mae says comparable sales "should have similar physical and legal characteristics when compared to the subject property," and then: "This does not mean comparable sales must be identical to the subject property." It allows sales from a competing neighborhood on one condition: "The appraiser must indicate the comparables are from a competing neighborhood and address any differences that exist." That is the working rule for a custom home here. An Alta Loma custom house may be compared with custom sales in Etiwanda or north Upland, each one named as a competing area and the location difference explained. A sale from Claremont, across the county line in Los Angeles County, is used only when it is genuinely better evidence, with the location adjustment explained.
The rule cuts both ways. Fannie Mae lists "failure to use comparable sales that are the most locationally and physically similar to the subject property" as an unacceptable practice. A planned-village tract house is close in distance but not in physical character, and a custom sale across town is the reverse. The report weighs the two and says which was given more weight and why.
Quality adjustments and the cost trap
When a comparable's quality differs from the subject's, the adjustment for that difference must be drawn from the market. Fannie Mae says "the appraiser's adjustments must reflect the market's reaction" and expects them "without regard to arbitrary limits on the size of the adjustment"; when adjustments are extensive, "the underwriter must determine if the opinion of value is adequately supported."
The trap on a custom home is cost. Superadequacy, or over-improvement, is a feature whose cost exceeds what it adds to the property in its market. Contributory value, what an improvement adds to the whole property in the market, is the measure the adjustment uses. Fannie Mae says the cost approach "may be appropriate" for new or proposed construction or a unique property, and that "appraisals that rely solely on the cost approach as an indicator of market value are not acceptable." A newly finished custom build may also be compared with builder sales; new construction appraisal in Upland covers that choice.
Where a reviewer pushes back
- A custom home compared with planned-village tract sales given the same quality rating when the photographs show otherwise.
- A quality adjustment with no market support summarized in the report.
- Construction cost presented as if it were value.
- Comparables from another area with no explanation of why that area competes with the subject's.
Two companion articles carry the same questions further: how a view is measured in Upland and whether a higher price tier changes the method.
Next step
The inspection runs 30 to 60 minutes for a standard single-family home, longer for hillside, custom, multi-family or homes with additions, and reports are typically delivered three to five business days from the inspection. The hillside and custom home appraisal page lists what the report includes. To start, send the address and the purpose of the report through the order form, or call (909) 324-6122. The fee is set by the scope of the assignment and quoted before work begins, and it does not depend on the value.
Sources
- Fannie Mae Selling Guide B4-1.3-06, Property Condition and Quality of Construction of the Improvements: https://selling-guide.fanniemae.com/sel/b4-1.3-06/property-condition-and-quality-construction-improvements (accessed November 6, 2026)
- Fannie Mae Selling Guide B4-1.3-08, Comparable Sales: https://selling-guide.fanniemae.com/sel/b4-1.3-08/comparable-sales (accessed November 6, 2026)
- Fannie Mae Selling Guide B4-1.3-09, Adjustments to Comparable Sales: https://selling-guide.fanniemae.com/sel/b4-1.3-09/adjustments-comparable-sales (accessed November 6, 2026)
- Fannie Mae Selling Guide B4-1.3-10, Cost and Income Approach to Value: https://selling-guide.fanniemae.com/sel/b4-1.3-10/cost-and-income-approach-value (accessed November 6, 2026)
- Fannie Mae Selling Guide B4-1.1-04, Unacceptable Appraisal Practices: https://selling-guide.fanniemae.com/sel/b4-1.1-04/unacceptable-appraisal-practices (accessed November 6, 2026)
- Freddie Mac, Uniform Appraisal Dataset (UAD) 3.6 FAQ: https://sf.freddiemac.com/faqs/uad-and-forms-redesign (accessed November 6, 2026)
- San Bernardino County Countywide Plan, San Antonio Heights: https://countywideplan.sbcounty.gov/community/valley-unincorporated/san-antonio-heights/ (accessed November 6, 2026)
Gordon Hall, California Certified Residential Real Estate Appraiser, BREA No. AR003877 (lookup: https://www2.brea.ca.gov/breasearch/faces/party/view.xhtml?id=23601). Reports are prepared in conformity with the Uniform Standards of Professional Appraisal Practice (USPAP). Nothing here is legal or tax advice; admissibility is always the court's decision.
Frequently asked questions
What is a tract twin, and why does a custom home not have one?
A tract twin is a house of the same builder's plan, often on the same street, whose sale gives a near-direct comparison. A custom home was designed and built one at a time, so no sale shares its plan, materials and lot. The appraiser compares it with sales of similar quality, size and setting instead.
How is construction quality rated on a custom home?
With a quality rating, the standardized Q1 to Q6 grade of design, materials and workmanship. Fannie Mae's Selling Guide describes Q1 as individually designed by an architect for a specified user and Q2 as often custom designed for an owner's site. The rating reflects the house as a whole, and each comparable is rated the same way.
Should I give the appraiser my plans and construction budget?
Plans, architect or builder information, and any geotechnical, retaining wall or grading reports help document what cannot be seen at the inspection. A budget describes what the house cost. It does not set the value, which comes from what buyers have paid for comparable houses.
Can comparables for an Alta Loma custom home come from Claremont?
Only when they are genuinely better evidence than closer sales, and then the report explains the location adjustment, because Claremont sits across the county line in Los Angeles County. Sales from competing foothill areas on the San Bernardino County side are usually considered first.
