California Residential Code (CRC)

The California Residential Code (CRC) is Part 2.5 of the California Building Standards Code (Title 24, California Code of Regulations). It is the dedicated code for detached one- and two-family dwellings and townhouses not more than three stories above grade plane with a separate means of egress, plus their accessory structures. The CRC is based on the International Residential Code (IRC) — the 2025 CRC tracks the 2024 IRC — with California-specific amendments adopted by HCD and other state agencies.

The 2025 California Residential Code is the current edition, effective January 1, 2026, replacing the 2022 CRC. Because the code is adopted on a three-year cycle and cities and counties may add local amendments, the exact requirements for your house, deck or ADU depend on the edition your jurisdiction has adopted and any local changes — which is exactly what GoCodebook reconciles for you.

Almost every question a homeowner or residential contractor asks lands in Chapter 3, Building Planning: room sizes and ceiling heights, egress windows, smoke and CO alarms, garage separation, glazing, guards and handrails, and wildfire construction. California renumbered much of Chapter 3 in the 2025 cycle, so citations you memorized under the 2022 CRC may point somewhere new — the chapter list below opens the adopted 2025 text.

The CRC is a self-contained code that consolidates building, energy, mechanical, plumbing and electrical provisions for low-rise homes into one document. Core areas include building planning (light, ventilation, ceiling heights, room sizes), means of egress and emergency escape and rescue openings (egress windows), smoke and carbon monoxide alarms, stairs, ramps, handrails and guards, decks and their attachment, foundations and footings, wall and roof-ceiling framing, and fire-resistant construction in wildfire areas.

Many remodels, additions, decks, re-roofs and ADUs are evaluated against the CRC. Single-family homes in California also generally require automatic fire sprinklers (NFPA 13D) and increasingly solar PV under the Energy Code. See where GoCodebook coverage is deepest for residential questions.

Use the CRC when your project is a detached one- or two-family dwelling or a townhouse not more than three stories above grade plane with a separate means of egress, or an accessory structure to one of those. Once a building exceeds three stories, has more than two dwelling units, or changes to a non-residential use, it generally falls under the California Building Code (CBC, Part 2) instead. Apartment and condominium buildings are CBC, not CRC.

ADUs are usually regulated under the CRC because they are accessory to a one- or two-family dwelling. A common rule trips people up: an ADU typically only needs fire sprinklers if the primary dwelling is sprinklered. Mixing up CRC and CBC scope is one of the most frequent sources of plan-check corrections — GoCodebook tells you which code controls and cites the section.

The CRC is where homeowners and contractors find the everyday rules: emergency escape and rescue (egress) window sizing for sleeping rooms and basements, smoke alarm and carbon monoxide alarm placement (in each sleeping room, outside each sleeping area, and on every level), guard and handrail heights, stair riser and tread dimensions, and deck ledger attachment and footing requirements that have tightened in recent code cycles after deck-collapse failures.

A single residential project usually triggers more than the CRC. Larger ADUs, complex electrical work and solar often pull in the California Electrical Code (CEC, Part 3), while administrative questions about adopted editions and amendments are governed by the California Administrative Code (CAC, Part 1). Ask GoCodebook and get the controlling section with a citation.

Four rules account for a large share of residential corrections. Emergency escape and rescue openings (Section R319) require a compliant opening in every sleeping room and in basements, with minimum net clear opening area, minimum width and height, and a maximum sill height above the floor. Smoke alarms (Section R310) must be in each sleeping room, outside each separate sleeping area, and on every story including basements — and an addition or alteration requiring a permit generally triggers alarms throughout the existing dwelling.

Carbon monoxide alarms (Section R311) are required in dwellings with fuel-fired appliances or an attached garage. Fire-resistant construction (Section R302) covers the dwelling-to-garage separation, townhouse separation walls, and the exterior-wall fire-resistance and opening limits driven by distance to the property line — the rule that most often constrains a small-lot house or an ADU pushed close to a side yard.

Decks are their own cluster. Section R507 sets ledger attachment, fastener schedules, joist spans, post-to-beam and post-to-footing connections, and lateral-load devices — provisions that tightened across several cycles after deck-collapse failures. Guards and window fall protection are in Section R321, and handrails in Section R320.

California adds requirements the base IRC does not have. Automatic sprinkler systems (Section R309) are required in new one- and two-family dwellings, installed to NFPA 13D. Solar photovoltaic systems (Section R329) and energy storage systems (Section R330) carry their own installation and access rules, layered on top of the solar mandate in the California Energy Code. Electric vehicle readiness is in Section R338.

Section R337 — Materials and Construction Methods for Exterior Wildfire Exposure is the residential counterpart to the wildfire hardening rules: Class A roofs, ember-resistant vents, ignition-resistant siding, eaves and decking for homes in a fire hazard severity zone. In the 2025 cycle those provisions were consolidated statewide into the new California Wildland-Urban Interface Code (Part 7), so check which text your jurisdiction is enforcing.

Residential work also picks up construction waste reduction (Section R334) and pollutant control (Section R340), which mirror CALGreen mandatory measures inside the residential code.

California's adopted codes — including the California Residential Code (CRC) — are published under Title 24 and hosted on code libraries such as UpCodes (up.codes) and ICC Digital Codes from the International Code Council (ICC). Those let you read the text section by section.

GoCodebook goes further: instead of searching a code library, you ask a question and get the controlling provision for the edition and local amendments your jurisdiction adopted, with a citation to verify. See how GoCodebook compares to UpCodes and ICC.