Where every figure on this site comes from

1 · The three tiers, and how much to trust each

The site's data is not uniform, and treating it as though it were is the fastest way to be misled by it. Three tiers, in descending order of confidence:

Only the first tier is what we would call parcel-grade. The other two are orientation: what the districts are called, who administers them and what they broadly permit. Per-tier limitations, including the cities we could not confirm, are set out on coverage and provenance.

2 · Chicago: cited by field, but not all from one source

The Chicago district pages are generated from a structured extraction rather than written by hand. Each district's floor area ratio, height limit, minimum lot area per unit, setbacks and parking requirement is stored with the section it came from, and the page renders the citation next to the figure. If a page says a district permits an FAR of 2.2, the section that says so is on the same line.

Which source each district was read from

This is the part most zoning products don't print, and it is the part that decides how much weight a figure can carry. The 53 districts were not all read from the same document:

Every district page states its own provenance under the spec sheet, so you never have to come back here to find out which of these applies to the district you're reading. One field, max_lot_coverage, is marked an approximation on every district and carries no ordinance section — it is a curated value, not a reading, and should be treated as the least reliable figure on the page.

The two badges

Independently of the source, each figure is labelled:

• verified — the ordinance states this value for this district in this field. It was read, not computed.
• approximation — the value is derived: calculated from other stated figures, or drawn from a standard expressed in prose rather than a bulk table. Directionally right, and not something to underwrite on without checking.

3 · The 50 states: statute first

Zoning power in the United States is delegated by states to local governments, and the terms of that delegation differ enough to matter — which is why the state pages lead with the enabling statute rather than with district names. Each was drafted from the state's own zoning enabling act and its recent reform legislation, then fact-checked against the statute text.

That review mattered. It removed several confidently-worded citations to acts that do not exist. We mention it because it is the honest characterisation of how this kind of dataset gets built, and because it is the reason the check exists as a required step rather than a nicety: a plausible statute number is exactly the kind of error that survives a casual read. Any statute added to this dataset in future goes through the same verification.

4 · The city layer: the GIS layer is the referee

City guides cover 306 cities with published district rosters, plus 21 where we deliberately publish no roster — either because the city has no conventional zoning at all (Houston being the well-known case) or because we could not establish one we trusted.

Each roster was drafted from the city's ordinance and then checked against the city's own zoning GIS layer — the set of district codes actually painted on the official map. This is the check that works, and it works because it is independent of the drafting: the map does not care what the ordinance's table of contents implies. Where the two disagreed, the map won.

Cities where no public layer was reachable are kept as drafted from the ordinance and flagged as unconfirmed on the coverage page. Every city guide also names that city's official zoning map and code, so you can check us in one click.

5 · What we refuse to publish

These topics come up constantly and we still don't give numbers for them, because they sit outside the corpus we have actually verified:

• Affordable Requirements Ordinance percentages and fees. The ARO lives in Chapter 2-44 of the Municipal Code, not Title 17. Our ARO explainer covers what triggers the obligation and stops short of the rates.
• Coach-house dimensional standards. Where an additional dwelling unit is permitted is in our corpus and is covered on the ADU page. The dimensional standards governing the structure are not.
• Department of Housing pre-certification. A Title 2 process, outside the zoning corpus.

Each of those pages says explicitly that the figure is out of scope rather than leaving a silence a reader might fill with an assumption. If you need those numbers, they exist — in the relevant chapter of the Municipal Code, and from the department that administers them.

6 · Telling us we're wrong

If a figure on this site contradicts the code, we want to know, and a specific report gets fixed fastest: the page URL and the section you believe we misread. Email team@realdevelop.io.

Chicago corrections are checked against the ordinance text; city roster corrections against that city's published zoning layer. Where a correction narrows what we can claim, we narrow the claim.

Every change to the data, and to what this site claims about it, is logged with a date — including the corrections that make us look worse. Read the data changelog →

Common questions

Which edition of the Chicago ordinance are the figures from?

Not all from one, and the district page tells you which. The manufacturing districts were read from Municipal Code of Chicago, Title 17 (Zoning Ordinance), edition 2026-S-73. The downtown districts were read from the City-published text in June 2026. The residential, business and commercial districts — the largest group — were read from a Title 17 excerpt inside a third-party zoning report dated 18 September 2024, which is the oldest source on the site. Every figure carries the section it was read from either way, so any single number can be checked against the code itself.

What is the difference between a verified and an approximation badge?

A verified figure is quoted from the ordinance text — the code states that number for that district in that field. An approximation is derived: computed from other stated values, or inferred from a rule expressed in prose rather than a table. Both are useful; conflating them would make the site look more authoritative and be less useful, so they are labelled separately on every field that carries one.

How were the 327 city district rosters checked?

Each roster was drafted from the city’s own zoning ordinance, then checked against that city’s published zoning GIS layer — the authoritative list of district codes actually in use on the map. Where the two disagreed, the GIS layer won and the roster was corrected. Where no public layer could be reached, the ordinance-sourced roster was kept and the city is flagged on the coverage page as unconfirmed.

Why do some pages refuse to give a number?

Because we could not source it. The Affordable Requirements Ordinance percentages and fees, coach-house dimensional standards and the Department of Housing pre-certification process all sit outside our verified corpus. Pages touching those topics say what the ordinance we have does establish, then stop. A plausible-looking number in a zoning report is worse than an admitted gap, because the reader cannot tell the difference until it costs them.

How often is the data refreshed?

The snapshot behind these pages was generated 2026-08-24, but that is when the data was exported, not when it was last read against the code — those are different dates and the second is the one that matters. Each district page states its own. Zoning codes are amended continuously, so any page here is a reading taken on a date, not a permanent fact; confirm a live deal against the currently adopted code.