Appraisal adjustments are the dollar amounts an appraiser adds to or subtracts from a comparable home’s recent sale price to account for the ways that comp differs from the property being valued. No two houses are identical, so the appraiser normalizes the comps: if a comp has a feature the subject lacks, value comes off; if the subject has an advantage, value is added to the comp. After adjusting three or more comps, the appraiser reconciles the modified prices into an opinion of market value the lender can rely on.
What an Adjustment Is and Which Way It Moves
The direction of an adjustment trips people up because it feels backward. You are not changing the subject property’s value. You are rewriting the comp’s sale price to answer a single question: what would this comp have sold for if it were identical to the subject?
So when a comp has a third garage bay, a finished basement, or an extra bathroom that the subject does not have, the appraiser subtracts from that comp’s price. The reasoning is simple: without those extras, that comp would have fetched less. When the subject has the advantage, value is added to the comp, because the comp would have sold for more had it matched. Every adjustment lands on the comp. The subject’s price is never touched directly.
Once each comp has been adjusted line by line, the appraiser reconciles the adjusted prices, giving the most weight to the comps that needed the fewest and smallest changes. A comp sitting a mile away in the same subdivision with one minor adjustment usually tells you more than a comp across town with six.
Which Comps Qualify in the First Place
Adjustments only matter if the comps are defensible to begin with. Fannie Mae requires comparables that closed within the last 12 months, drawn from the same neighborhood or a competing market area whenever possible. The appraiser reports each comp’s distance and direction specifically, such as “1.75 miles NW” rather than “nearby.”1Fannie Mae. Comparable Sales Rural or unusual properties sometimes force a wider search, and any such stretch has to be justified in writing.
Recency is not everything. An older sale that closely matches the subject and only needs a time adjustment can be more reliable than a fresh sale that requires adjustments on five different lines.
What Actually Triggers an Adjustment
Physical differences drive most adjustments. Gross living area, meaning finished square footage above grade, is usually the single biggest line. A 200-square-foot gap between two otherwise similar homes easily translates into a five-figure adjustment once the local price per square foot is applied. Bedroom and bathroom counts follow, since an extra full bath or a fourth bedroom measurably shifts buyer demand. Lot size, garage capacity, and the age of the structure appear on nearly every grid.
Condition and Quality Ratings
The Uniform Appraisal Dataset (UAD) standardizes how appraisers describe condition and construction quality, so loose words like “good” or “average” no longer control the adjustment. Condition runs on a six-point scale:
- C1: brand-new construction, never occupied, no physical depreciation.
- C2: no deferred maintenance; essentially like-new or recently renovated to current standards.
- C3: well maintained with limited wear; some components may have been updated.
- C4: minor deferred maintenance and normal wear; adequately maintained with only minimal cosmetic or mechanical repair needs.
- C5: obvious deferred maintenance requiring significant repairs; livable but functionality is diminished.
- C6: substantial damage or deferred maintenance severe enough to affect safety, soundness, or structural integrity.
Construction quality uses a parallel Q1 through Q6 scale, running from unique, architect-designed homes with exceptionally high-grade materials down to basic structures sometimes built without plans using the lowest-cost materials. Most tract-built homes land around Q4, meaning they meet code with standard builder-grade finishes.2Freddie Mac. Uniform Appraisal Dataset When a comp rates C3 and the subject rates C4, the appraiser subtracts from the comp because the comp’s superior condition inflated its sale price relative to what the subject would command.
Location
Two homes a quarter mile apart can sit in very different markets if one is on a quiet cul-de-sac and the other backs a highway interchange. Location adjustments cover proximity to busy roads, views, school district boundaries, flood zones, and neighborhood desirability. Because location cannot be changed, underwriters scrutinize these more closely than most other lines. The appraiser has to show, with actual sales data, that buyers pay measurably more or less for the locational difference being adjusted.
Seller Concessions
When a seller pays part of the buyer’s closing costs or offers other financial incentives, those concessions can push the recorded sale price above what the property alone is worth. Fannie Mae requires appraisers to adjust comps with seller concessions downward to strip out the artificial boost.3Fannie Mae. Adjustments to Comparable Sales The adjustment should equal the amount by which the concession inflated the price, which is not automatically the same as the concession’s full dollar cost. If market analysis shows the full concession amount flowed into the price, a dollar-for-dollar deduction is acceptable, but that conclusion has to be supported. Positive adjustments for concessions are never permitted.
Market Conditions (Time)
Prices move between the day a comp closes and the day the appraisal is dated. In a market where values rose 5% over the past year, a comp that sold nine months ago usually needs an upward time adjustment to reflect current conditions. Fannie Mae’s Selling Guide specifically allows an older sale with one well-supported time adjustment to be the stronger comp over a recent sale requiring multiple feature-based adjustments.1Fannie Mae. Comparable Sales
How Appraisers Calculate the Dollar Amounts
Adjustment values do not come from a chart. They come from market analysis, and the methods range from straightforward to statistically involved. Fannie Mae requires that every adjustment reflect the market’s actual reaction to a feature difference. Using a rule-of-thumb figure like “$20 per square foot” when market data shows the adjustment should be $100 per square foot is explicitly called out as inappropriate.3Fannie Mae. Adjustments to Comparable Sales
Paired Sales Analysis
The most intuitive method. The appraiser finds two properties that are nearly identical except for one feature and attributes the price gap to that feature. If two homes in the same subdivision sold three months apart and the only meaningful difference is a two-car garage versus none, the gap isolates what the market pays for a garage. Perfect pairs are rare in practice, so appraisers usually have to account for minor secondary differences before attributing the remainder to the target feature. Several pairs pointing to the same number strengthen the conclusion.
Regression Analysis
When enough sales data exists, appraisers and automated valuation models use regression analysis to measure how individual features affect price across a broader dataset. Multiple regression can account simultaneously for square footage, bedroom count, lot size, and other variables, producing an adjustment for each. The method depends on a healthy ratio of sales to variables. Many analysts work from a minimum of 10 to 15 sales per variable being tested; anything below a 4-to-1 ratio risks overfitting, where the model reflects quirks in the sample rather than genuine market behavior.4Appraisal Institute. The Appraisal of Real Estate, 15th Edition – Appendix B: Regression Analysis and Statistical Applications
Depreciated Cost Method
For features like a swimming pool or a sunroom addition, the appraiser may calculate what the feature would cost to build today and then subtract depreciation for age and wear. A pool that cost $50,000 eight years ago might contribute only $20,000 to market value now. This approach is most useful when paired sales data for the specific feature is thin, and it keeps the adjustment anchored to current contributory value rather than original spend.
The 10/15/25 Rule Is a Myth
If you have spent any time reading about appraisals, you have probably seen the claim that Fannie Mae caps single-line adjustments at 10%, net adjustments at 15%, and gross adjustments at 25% of a comp’s price. Fannie Mae’s Selling Guide says the opposite: “Fannie Mae does not have specific limitations or guidelines associated with net or gross adjustments. The number and/or amount of the dollar adjustments must not be the sole determinant in the acceptability of a comparable.”3Fannie Mae. Adjustments to Comparable Sales
What Fannie Mae does require is that adjustments be market-based and defensible. The appraiser has to analyze competitive properties and support each adjustment with data rather than arbitrary benchmarks. When a property is genuinely unique and no close comps exist, the appraiser should select the best available indicators of value and make supported adjustments, explaining the reasoning in the report.
So where did 10/15/25 come from? Those thresholds originated as internal lender guidelines and risk-management flags. Many banks and mortgage companies still use them inside their underwriting software, so an appraisal that exceeds those percentages triggers a closer review or a request for more explanation. That is a lender overlay, not a Fannie Mae rule. An appraisal with a 30% gross adjustment can be perfectly acceptable if the appraiser documents that those were the best comps available and that each adjustment is market-supported. The reverse is also true: an appraisal with small adjustments can still be rejected if the comps themselves are poor choices.
Accessory Dwelling Units Get Their Own Line
ADUs are treated differently from extra bedrooms or bonus rooms. To qualify as an ADU, the space must be self-contained, with its own entrance, kitchen (at minimum cabinets, countertop, sink with running water, and a stove or stove hookup), sleeping area, and bathroom. Only one ADU is allowed per parcel, and it must be smaller than the primary home. Its living area cannot be folded into the primary dwelling’s above-grade square footage; it goes on a separate line in the sales comparison grid and is adjusted independently based on contributory value.5Fannie Mae. Improvements Section of the Appraisal Report The one exception: if the ADU is inside the primary dwelling with interior access and sits above grade, its square footage can be included in the main calculation.
When Adjustments Produce a Low Value
A low appraisal is one of the more stressful moments in a transaction. The core problem is simple: your lender will not loan more than the appraised value, so if the appraisal comes in at $285,000 on a $300,000 purchase, you have a $15,000 gap. Your practical options:
- Negotiate the price down to the appraised value or meet somewhere in the middle. Sellers of homes that have been sitting are more likely to agree.
- Cover the gap in cash at closing. The loan is based on the lower appraised value, so your effective down payment grows.
- Request a reconsideration of value if you believe the appraiser missed relevant comps or made errors.
- Walk away, if your contract includes an appraisal contingency. Without the contingency, you risk forfeiting your earnest money.
How a Reconsideration of Value Works
A reconsideration of value (ROV) is the formal process for challenging an appraisal you believe is unsupported, deficient, or potentially discriminatory. Fannie Mae now requires every lender to have written ROV policies and procedures, and the lender must disclose the ROV process when it delivers the appraisal report.6Fannie Mae. Appraisal Quality Matters
To start one, submit a written request to your lender with your name, the property address, the appraisal’s effective date, the appraiser’s name, and the date of your request. The substantive piece is identifying exactly what you believe is unsupported or inaccurate and providing additional data, usually comparable sales the appraiser may have missed. You can submit up to five additional comps. Each needs a data source reference such as an MLS listing number, and you have to explain why those comps better support a higher value.
Only one borrower-initiated ROV is permitted per appraisal, so your submission has to count. The lender must have a designated underwriter or appraisal expert review your request before forwarding it to the appraiser. The appraiser then evaluates the new data and either revises the report or explains in writing why the additional information does not change the value conclusion.
If you believe the appraisal reflected racial, ethnic, or other prohibited bias, you can submit a complaint to the Consumer Financial Protection Bureau or contact the Department of Justice’s fair housing division. Both the Fair Housing Act and the Equal Credit Opportunity Act apply to the appraisal process.7Consumer Financial Protection Bureau. Protecting Homeowners From Discriminatory Home Appraisals