Code as Shared Rules

Draw the same apartment corridor in Dallas and in Houston and you are not checking it against the same book. Both cities start from the International Building Code (IBC). Dallas enforces the 2024 edition with North Texas regional amendments; Houston enforces the 2021 edition. The rules are shared. The law is whatever each city adopted, in which edition, with which local changes, starting on which date.

Which edition governs this room

Which edition governs comes from the repo's Texas adoption record (researched April 2026): a 2012 IBC statewide minimum; Houston on the 2012 IBC until the 2021 IBC took effect on January 1, 2024; Dallas listed on the 2024 IBC with no effective date, so Dallas is only checked at the April 2026 record date. The packs are hypothetical: their room-width minimums (8, 10 and 12 ft) and the 3 ft door are invented to show the mechanism; they are not quoted IBC provisions, a comparison of what the editions actually changed, or a compliance opinion. Room depth remains 16 ft.

I first wrote this thesis as “the building code is open-source law.” That title was too generous, which is why this edition is called Code as Shared Rules. The old one made two claims I can’t defend. The code is shared, but it isn’t open source in the software sense. And the edition is not a detail you can look up later; it is part of the design input.

Who This Matters To (And Why)

Critical: Architect, City, GC. They draw, adopt and build against a specific edition. Get the edition wrong and the drawings are wrong, even if every dimension is right.

Important: Engineer, Inspector, Developer. They inherit the edition chosen at application and live with its amendments.

Context: Banker, Investor, Interior Design. A portfolio across several cities is a portfolio across several code editions.

Highest typology impact: Multifamily, Office, Industrial, Hotel. Lower impact: Retail, Mixed Use.

Shared Text, Local Law

A model code is a book written by a private standards body. The International Code Council (ICC) writes the I-Codes, including the IBC, the IRC (residential) and the IFC (fire). NFPA writes the National Electrical Code and the Life Safety Code. A new I-Code edition appears every three years: 2012, 2015, 2018, 2021, 2024. A model code binds no one until a state or city adopts it by statute, regulation or ordinance, usually with amendments and an effective date of its own.

That gives every project four facts to pin down: the jurisdiction, the base edition, the local amendments, and the date that decides which of those apply. The shared part is the base text. The amendments and dates are local.

One State, Four Editions

Texas makes the point better than any analogy. As of April 2026, city and state adoption records show a 2012 IBC statewide minimum. Cities adopt above that floor on their own schedules:

• 2024 IBC: fourteen Dallas–Fort Worth cities, including Dallas, Fort Worth, Arlington and Plano, plus Austin, San Antonio, McAllen and Pasadena. The DFW cities share regional amendments coordinated by the North Central Texas Council of Governments (NCTCOG), but each city still adopts them individually.
• 2021 IBC: Houston, El Paso, Corpus Christi, Laredo, Lubbock, Tyler and others.
• 2018 IBC: Brownsville and Odessa.

Houston enforced the 2012 IBC until January 1, 2024, then jumped straight to 2021, skipping two editions. Austin adopted the 2024 IBC in May 2024, and it took effect on July 10, 2025. For fourteen months, Austin’s adopted code and its enforced code were different editions. One state, one model code family, and four editions on the books, from the 2012 floor to 2024.

The software analogy that survives is version pinning, not forking. Houston doesn’t maintain its own IBC. It pins an older release and patches it with local amendments. The DFW cities pin the same release and share one patch set, which is the closest thing to a shared dependency this industry has.

Some states go further. California doesn’t enforce the ICC books directly. It republishes them as Title 24. The 2025 California Building Code, effective January 1, 2026, is the 2024 IBC with California amendments. In the first version of this post I called California’s energy code a fork of the International Energy Conservation Code (IECC). That was wrong: Part 6 is California’s own code, not the IECC. New York State enforces one Uniform Code, the 2025 edition based on the 2024 I-Codes and effective December 31, 2025, everywhere except New York City, which keeps its own building code.

Why Not “Open Source”

The “open source” half of the old title doesn’t survive the copyright page. The ICC and NFPA hold copyright in their model codes and sell them. The development process is public: outsiders can propose changes and argue for them at open hearings. But the ICC’s final votes belong to its governmental members, who are mostly code officials, not to whoever shows up. That is closer to public comment on a privately published standard than to a pull request against a GPL repository. The old version said anyone can read the code “in full without paying for access to proprietary standards.” At best that is incomplete. Free read-only viewing online exists; NFPA’s, for one, requires a sign-in and doesn’t let you download or print. And the standards a code cites are often sold separately. The analogy still earns something narrow: the text can be read, discussed and revised through a public process. Read it as a metaphor for access and revision, not a claim that public availability settles interpretation. Adoption, amendments, enforcement and professional review give the rules their local effect.

What changes once a jurisdiction adopts a code? The adopted text is binding law, and courts have had to decide who may copy it. In Veeck v. Southern Building Code Congress International, 293 F.3d 791 (2002), the full Fifth Circuit, sitting en banc, held that Peter Veeck could post the building codes two small Texas towns had adopted. As enacted law, the court said, those codes were in the public domain. As model codes, they kept their copyright. The court distinguished a harder case: a law that only refers to a separately written standard and sends you off to consult it.

That harder case is American Society for Testing and Materials v. Public.Resource.Org, in which ASTM, NFPA and ASHRAE sued a nonprofit that posted standards incorporated by reference into law. In 2018 the D.C. Circuit sent the case back for a closer fair-use analysis and left open whether incorporated standards keep their copyright (896 F.3d 437). In 2023 it held that non-commercial posting of standards incorporated by reference into law is fair use (82 F.4th 1262). It still did not decide the copyright question, and fair use is narrower than declaring the standards public domain. I’m an architect, not a lawyer. The practical point is that “the law” and “the book the law points to” are different objects with different reading rights.

What the Study Shows

The reader study for this thesis holds one room fixed at 16 ft deep and asks where and when it is being permitted. Pick the Texas statewide minimum, Houston or Dallas, and slide the permit-application date between January 2023 and April 2026. The edition follows the Texas adoption dates above: the 2012 IBC at the state floor; in Houston the 2012 IBC through December 2023 and the 2021 IBC from January 1, 2024; in Dallas the 2024 IBC at the April 2026 date. No effective date is given for Dallas’s 2024 adoption, so for an earlier Dallas application the study declines to check the room and says why. That refusal is the thesis in small: without a pinned edition and date there is nothing to check against.

Each edition then hands the room a rule pack. The 2012 pack asks for a room at least 8 ft wide, the 2021 pack 10 ft, the 2024 pack 12 ft, and every pack asks for a door of at least 3 ft. In April 2026 a 10 ft room with a 3 ft door passes in Houston and fails in Dallas, 2 ft short. A 9 ft room in Houston passes on a December 2023 application and fails by 1 ft on a January 2024 one. Nothing in the drawing moved. Only the place or the date did. That is the Dallas-versus-Houston problem at the scale of one room.

Only which edition applies, and from when, comes from the adoption dates. The packs’ numbers are hypothetical teaching constraints, not quoted IBC provisions or a comparison of what the editions actually changed; no real edition differs by a room-width rule like this.

Machine-Readable Rules Need Provenance

The original thesis said a machine-readable code makes compliance “deterministic.” Much of the code is arithmetic: occupant loads, exit counts, travel distances and widths. That part can and should be encoded once and run continuously while you draw. It is not all arithmetic. Building officials interpret provisions and approve alternative methods. A rule engine that reports pass or fail without naming the jurisdiction, edition, amendments and effective date it checked is linting against the wrong book with total confidence.

The Judgment

Treat a project’s code basis as a pinned dependency. Before drawing the first egress path, write down the jurisdiction, base edition, local amendments, and the date that fixes them. That date is usually tied to the permit application, but check the jurisdiction’s transition rules. Then tie each requirement to the occupancy and project conditions it applies to, and record the source and authority behind it. A firm working in Dallas and Houston on the same unit plan is maintaining two builds of one product. The shared rules let you reuse most of the design. The local adoption tells you which parts you can’t reuse.