BMO (Baseline Mansionization Ordinance)

City of LA rules limiting the size of single-family homes in non-hillside R1 zones. Browse the full construction glossary for related terms.

BMO (Baseline Mansionization Ordinance) comes up in the zoning and land-use side of nearly every Greater LA and Bay Area project we touch. The Baseline Mansionization Ordinance caps the size of single-family homes in flat-lot R1 zones to prevent oversized 'McMansions.' It works through a tighter FAR (typically 0.45 plus a 20% bonus for green-building features) and stricter side-yard setbacks for second stories. Getting it right at design saves rework later — getting it wrong is one of the most common reasons permits stall. See how it lands in our five-phase process and the relevant field guides.

Most owners run into BMO (Baseline Mansionization Ordinance) during the design or plan-check phase — specifically inside schematic design or permit submittal. Your project manager flags it on the schedule, walks you through what the city expects, and confirms documentation is in place before the inspection that depends on it.

Sometimes — depends on whether it adds scope (a report, a structural detail, a fee) or just a paperwork step. Anything cost-impacting is itemized in your contract or change order, never buried in the invoice. Sanity-check your number with the ADU cost calculator and the 2026 cost report.

The project architect owns design-level decisions; the permit runner owns city interactions — see the California permit directory; the project manager owns field execution. You always know who to ask. Start a conversation on the contact page.

Most often during permit submittal or early construction. The full sequence is on the process page.

Yes — local interpretation varies. The LA studio and Bay Area studio note the regional shifts on each city hub.

City-specific — the California permit directory lists the form set per jurisdiction. Field journal entries show what actually clears plan check.

Architect, structural engineer, or Title 24 consultant — depends on the term. The process page maps roles across the five phases.

Direct line item in the contract when it triggers a report, detail, or fee. Pricing bands are in the 2026 cost report.

California ADU and remodel law has shifted every legislative session since 2017. Material changes land first on the field journal; definitions update quarterly here.

Each glossary entry cites the relevant Gov Code, building code section, or city bulletin. The permit directorylinks the source portals.

Cross-references live on the ADU types index. The term often appears in detached ADU and JADU contexts most.

Yes — use the contact page. We add the most-asked questions to the site-wide FAQ monthly.

Each entry cross-links 3–5 related terms. Browse the full set on the glossary index.