Methodology
How a report is built, what every number means, what we calculate ourselves — and, just as importantly, what this data cannot tell you.
Where the data comes from
Every figure in a report is drawn from New York City's public records, published as open data by the city itself. We do not license private data, we do not scrape brokerages, and we do not estimate values with a model. If a number appears on a report, it appears because the city published it.
A report pulls together records covering:
- Ownership and registration — the registered owner of record and the parties on file for the building.
- Recorded documents — deeds, mortgages and assignments recorded against the lot, with dates and amounts.
- Assessment and tax — assessed land and total value, taxable value, market value and the tax class, for each published assessment period.
- Housing and building violations — issued violations, their status, and the outstanding balance where one is recorded.
- Complaints — complaints logged against the property and their disposition.
- Permits and alterations — filed and issued work, and its current status.
- Zoning and land use — district, lot and building dimensions, floor-area ratios, and landmark status.
- Occupancy — unit counts, building class, and year built.
- Legal — housing-court proceedings recorded against the property, and whether the lot appears on the tax-lien sale list.
We deliberately do not print the names of the specific city departments, datasets or programs behind each record. It adds nothing for the reader and invites the assumption that this site is an official one. It is not — see About.
What we calculate ourselves
Aggregation on its own is not analysis. The figures below appear in no city dataset — they are computed by PropertyDiSHi from the raw records, and they are the reason a report tells you something a pile of public files does not.
Unused floor-area ratio (unused FAR)
Zoning permits a maximum floor-area ratio for each allowed use. The gap between what is built and what is allowed is the development headroom on the lot — the single most consequential number for anyone thinking about adding to a building.
Unused buildable area
Unused FAR expressed in square feet, which is how it is actually traded and financed:
This is an as-of-right ceiling under the lot's floor-area limits. It is not a promise that the space can be built. Height and setback limits, landmark status, lot coverage, yard requirements and existing tenancies can all reduce it to zero. Treat it as the upper bound of a conversation, not a plan.
Assessed value trend
We take the assessed values across every published assessment period we can retrieve (up to the twenty most recent), sort them newest first, and compute the change over time. A sharp move in assessed value usually precedes a corresponding move in the tax bill.
Assessed building value
Estimated annual tax levy
This is an estimate, not a bill. It applies the published rate for the property's tax class to its taxable assessed value. It does not know about exemptions or abatements the property may carry, it does not include interest or arrears, and it will not match a real bill to the dollar. It is here to give you the order of magnitude.
The risk rating
The risk rating is calculated, not judged — and deliberately so. We tried letting a language model assign it and the result was useless: it rated almost every building "medium", and gave the same building different answers on different days. A rating that never varies and never reproduces is not a rating.
So it is derived from the figures, by these rules, and it is identical every time:
The written analysis explains that rating. It does not decide it, and it is not permitted to disagree with it — we overwrite the model's answer with ours before anything is shown. You can therefore check any rating on this site against the numbers on the page and the rules above, and get the same answer we did.
Per-unit and price ratios
Useful for sanity-checking a building against its neighbours. Both are only as good as the last recorded sale — see the limitations below.
Known limitations
These are the things most likely to mislead you. We would rather you heard them from us.
We report open violations only — and that is a deliberate choice
A closed violation is a problem that was raised and then fixed. Every century-old building has accumulated hundreds, and the lifetime total therefore measures a building's age, not its condition. We do not publish it, because a large number that means nothing is worse than no number at all. Every violation figure on this site is the count that is open now, taken directly from the status recorded against each violation — not inferred. And an open count only becomes meaningful once you divide it by the number of apartments, which is why we do that for you.
"Penalties owed" is two separate debts — and still not everything
We show both, because most sources show only the first and it badly understates what a building owes:
- Enforcement penalties — fines attached to summonses.
- Safety-violation penalties — standing debts for unfiled boiler, elevator, facade and energy reports. These accrue quietly, they are routinely missed, and they are frequently the larger of the two. On one building we tested, the enforcement balance was $1,250 and the safety penalties were $3,000 — so the commonly-quoted figure was understating the debt by a factor of three.
Where the safety figure cannot be retrieved for a property, we show "Not available" and withhold the total. We will not show a total that quietly omits half of it, because a number that looks complete and isn't is worse than no number at all.
And neither figure includes unpaid property tax or water and sewer arrears, which are often the largest debt of all and appear nowhere on this site. A property can show zero penalties here and still owe the city a great deal. Never read anything on this page as a payoff amount.
"Liens" means the tax-lien sale list, not every lien
We report whether the lot appears on the city's tax-lien sale list. Mortgages and other encumbrances are not extracted — they appear only as recorded documents in the Documents section, which you must read yourself. This is not a title search, and it is not a substitute for one.
A blank field means "no value on record" — not zero
Where the city has published nothing for a field, we show a dash rather than inventing a zero. A violation with no recorded penalty shows a dash because no penalty is recorded, not because the penalty is $0.
Records are as complete as the city's are
Records are filed with a lag, they are sometimes filed against the wrong lot, and they are sometimes not filed at all. Work done without a permit does not appear in the permit history. A recent sale may not yet be recorded. Absence of a record is weak evidence, and we will not dress it up as a clean bill of health.
The last recorded sale is not a valuation
A recorded transfer may be a genuine arm's-length sale, or it may be a transfer between related parties, a correction, or a nominal deed for $0 or $10. We report what was recorded. We do not judge whether it reflects market value, and neither should any ratio derived from it.
Freshness
Reports are assembled from the city's current published records when you request one, and the result is cached for a short period so that repeat views are fast. The date a report was generated is recorded with it. Because the underlying records are themselves updated on the city's schedule and not ours, a report reflects what the city had published at that moment — no more, no less.
Written analysis
Where a report carries a short written summary of a property's strengths and weaknesses, that summary is generated by a language model from the property's own figures — the same numbers shown on the page — and it is labelled as such. It introduces no facts of its own: every figure it cites appears in the report above it, and we check that automatically before the summary is ever shown.
It is a reading of the data, not a professional opinion, and it can be wrong about emphasis even when it is right about arithmetic. The numbers are the product. The summary is a convenience.
This is a research tool, not advice
Nothing here is legal, financial, tax or investment advice, and nothing here substitutes for a title search, a survey, a lawyer or a licensed inspection. If a number matters to a decision you are making, verify it at the source before you act on it. See Terms.
Found a figure you believe is wrong? Tell us and we will look at it — get in touch.