How to Read a Matrix Adoption Table — Does This Rule Even Apply?

Open almost any chapter of the California Building, Mechanical, Plumbing, or Electrical code and the first thing you hit is a dense grid of Xs. Most code users scroll right past it. That's a mistake — the grid is a Matrix Adoption Table (MAT), and it answers the question that comes before every other one: does this rule even apply to my project?

What the grid actually is

California is unusual. It's one code — Title 24 — but roughly a dozen state agencies write pieces of it, and not every agency adopts every section. The MAT is how the code shows you who adopted what. It sits at the head of each chapter, and the code is explicit that it belongs there:

Verified against the California Green Building Standards Code, "Effective Use of This Code": "Sections of this code which are applicable and adopted by each state agency are identified in the Matrix Adoption Tables located at the beginning of each chapter."

The table is labeled "non-regulatory, intended only as an aid to the code user." It doesn't add requirements — it maps them. Each column is an adopting agency. Each row is a section. An X in a column means that agency adopted that section.

Read the row, find your column

The columns depend on the book. In the California Electrical Code's Article 517, the header columns are BSC, BSC-CG, SFM, HCD, DSA, OSHPD, and DPH — with sub-designations underneath (DSA splits into AC / SS / SS/CC; OSHPD into 1, 1R, 2, 3, 4, 5, 6). The Plumbing and Mechanical books carry more columns still — AGR, DWR, CEC, and others — because more agencies touch that material.

Three control rows sit at the top of every table:

• Adopt Entire Chapter — the agency takes the whole chapter as written.
• Adopt Entire Chapter as amended — the agency takes the chapter, but with California changes; the amended sections are listed below.
• Adopt only those sections that are listed below — the agency takes just the rows that follow.

Here's how that reads in practice, using Article 517 (Health Care Facilities):

Verified against the live Article 517 Matrix Adoption Table (California Electrical Code): the Division of the State Architect adopts the entire article, while the State Fire Marshal and OSHPD adopt it as amended and then list the exact sections that carry California changes. The BSC and HCD columns are blank — this article was never theirs.

So if you're reviewing a DSA project, Article 517 applies wholesale. On the hospital (OSHPD) side, you follow the listed amendments. And if a rule has no X in your agency's column, it isn't yours — don't write the correction.

The italics are doing work

One more marker. In the MAT, a section number printed in italics flags a California amendment — that section differs from the base model code. The same number in regular type generally means the agency adopted the model-code language as written — though, as the January 2026 errata showed, the grid isn't always perfect, and a plain-type row can turn out to be a California addition too.

Verified against Article 517: sections such as 517.1(A) and 517.4 are printed in italics — the California-amended entries — set apart from the sections printed in plain type.

The Building Standards Commission says the same thing in plainer words: learn "the various margin markings, banners and text styles that … indicate … what amendments are model code changes versus California amendments."

A five-minute workflow

The code spells out the steps:

1. Establish the occupancy.
2. Find which agency has authority over it — the state-agency authority list lives in Chapter 1 of the book you're in.
3. Go to the chapter that covers your work.
4. Read the MAT — find your agency's column, confirm the section is adopted for your building type, and note whether it's italicized (amended) or plain (model code).

This is the companion to a question answered earlier: who owns which Part of Title 24. That piece tells you which agency writes each book. This one is the next move — reading the per-chapter grid to see whether a specific section landed in your lane.

Why this is the errata's tell

If you want proof the grid matters, look at what the January 2026 Title 24 errata actually fixed. Several corrections were MAT and agency-banner cleanups, not new rules:

• In the California Electrical Code, Article 517's table was reworked — OSHPD 1, 4, and 5 adoption moved from 517.1(B) to 517.1(C), and a batch of sections were newly identified as state amendments.
• In the California Plumbing Code, a BSC and DSA-SS amendment in Table 422.1 was relocated to footnote 9.
• Individual agency banners were corrected too (517.29, 517.34, 705.20, 708.1).

None of that changes a dimension or a load. It changes who a rule applies to — which is exactly what the MAT exists to tell you. When the stakes are high, confirm the adopting-agency banner against the current book and verify with your local jurisdiction, since a city amendment can sit on top of any section.

What CrossBeam does with it

CrossBeam reads every section of Title 24 the way a plan checker has to — by which agency adopted it and for which occupancies, not just what the text says. So a requirement that was never adopted for your project type doesn't become a correction, and one that was doesn't get missed.