# What Are the Major Changes in the 2025 California Residential Code (CRC) Author: Lovekush Gangwar Author URL: https://www.meltplan.com/blogs/author/lovekush-gangwar Published: 2026-08-25 Category: Code Research Category URL: https://www.meltplan.com/blogs/category/code-research Meta Title: What Are the Major Changes in the 2025 California Residential Code (CRC) Meta Description: What changed in the 2025 CRC? Explore major updates to residential design, structural rules, envelopes, ADUs, tiny houses, electrification, PV/storage readiness, and more. Tags: coderesearch, buildingcodes Tag URLs: coderesearch (https://www.meltplan.com/blogs/tag/coderesearch), buildingcodes (https://www.meltplan.com/blogs/tag/buildingcodes) URL: https://www.meltplan.com/blogs/what-are-the-major-changes-in-the-2025-california-residential-code-crc The **2025 California [Residential Code](/blogs/applying-the-california-residential-code-crc-stairs-decks-adus-and-remodels) (CRC)** introduces wide-ranging updates affecting structural design, construction methods, energy resilience, accessory structures, detached dwellings, and modern residential technologies. The most significant themes include: 1\. Reorganized Core Chapters (especially Chapter 3) The CRC reclassifies and relocates numerous provisions for clarity, tightening definitions for dwelling units, habitable rooms, mezzanines, and accessory structures. 2\. Expanded Requirements for Carbon Monoxide, Smoke Alarms, and EERO (Emergency Escape & Rescue Openings) Electrical-only homes, sleeping lofts, and certain additions now have different or clarified requirements. 3\. New Appendix Chapters Added The 2025 CRC adds **entirely new appendices**, including: - **Appendix BL – Tiny Houses** (modernized, aligns with national IRC Tiny House Appendix Q) - **Appendix BM – Existing Buildings for Residential Only** - **Appendix BN – Relocated or Moved Dwellings** - **Appendix CG – PV + Storage Ready Homes** These significantly expand residential design options. 4\. Major Overhaul of Building Envelope Requirements (Chapter 7) WRBs, vapor retarders, and moisture protections receive major updates. 5\. Decks, Guardrails, Loft Access, and Stair Geometry Modernized Structural capacities, guardrail load criteria, and loft/stair access now follow contemporary safety standards. 6\. New Provisions for Electrification & Battery Systems Residential readiness for electrification is strengthened. Overall, the 2025 CRC increases clarity, modernizes provisions, supports advanced residential systems, and resolves long-standing enforcement ambiguities. # Chapter 1  -  Administration ### High-Impact Summary  -  Chapter 1 The 2025 CRC revises administrative language to align with the 2024 IRC model code while preserving California-specific amendments. Major themes: - Clarified applicability for **existing structures, relocated dwellings, and ADUs** - Revised authority for **building officials**, especially referencing storm, earthquake, and emergency conditions - Updated requirements for **construction documents**, including digital submissions - Revised definitions and applicability for **residential-only enforcement** ### Full Detailed Table of All Changes  -  Chapter 1 SectionChange TypeDescriptionImpactR101.2Revised ScopeLanguage updated to better reflect applicability to 1- and 2-family dwellings and townhouses ≤3 stories.Clarifies enforcement boundaries; removes ambiguity around mixed-use conditions.R102.7Existing StructuresUpdated clarification that existing structures must comply with the code provisions in Appendix BM (new).Aligns the main body of CRC with the new Appendix for existing buildings.R102.7.1 (NEW)Moved / Relocated StructuresNow directly references Appendix BN for moved/relocated dwellings.Creates explicit compliance pathway for relocation projects.R104Duties of Building OfficialExpanded to include digital plan review, emergency directives, and climate/disaster mitigation authority.Empowers AHJs in wildfire, flood, earthquake, and high-wind events.R105PermitsNew clarifications for work exempt from permits (e.g., certain energy storage prep work, small accessory projects).Streamlines small projects and ADU support structures.R106.1Submittal DocumentsExplicit acceptance of digital construction documents; clearer engineering criteria.Reflects modern plan-check workflows.R109InspectionsClarified special inspection coordination with CRC-specific provisions (rather than CBC Ch. 17).Ensures one- and two-family inspection processes are less CBC-dependent.R115–117 (NEW/Updated)Unsafe Structures, Stop Work, EmergenciesModernized enforcement language for partial evacuation, post-disaster assessment, and immediate hazards.Important for wildfire, seismic, and landslide-prone zones. ‍ ### Expert Commentary  -  Chapter 1 #### 1\. Appendix BM and BN references are new - and important These appendices govern existing homes and moved dwellings. The 2025 CRC integrates them fully into the administrative chapter. #### 2\. Digital plan review becoming normalized Local AHJs were inconsistent about digital submissions during COVID-era transitions; CRC 2025 codifies digitization. #### 3\. Disaster response authority expanded Reflects California’s extreme climate, wildfire, and seismic realities. #### 4\. Clearer permit exemptions will meaningfully reduce permit backlogs This is particularly important for: - Light accessory structures - Solar-readiness upgrades - Battery-ready infrastructure # Chapter 2  -  Definitions ### High-Impact Summary  -  Chapter 2 Themes in CRC 2025: #### 1\. New definitions for modern residential technologies Including **PV-ready**, **storage-ready**, and **electrification-ready** homes. #### 2\. Clarification of key residential terms Especially: - Habitable space - Dwelling unit - Sleeping loft (important given Appendix P from CBC and Appendix BL here) #### 3\. Revisions aligning CRC with new appendices Definitions now reference Appendices **BL**, **BM**, **BN**, and **CG**. #### 4\. Improved clarity around fire safety and egress-related definitions Supporting updates in Chapters 3, 7, 9, and 10. ### Full Detailed Table of All Changes  -  Chapter 2 DefinitionChange TypeDescriptionImpactAdjacentRevisedLanguage clarified to prevent misinterpretation in lot-line, wildland-urban interface, and fire separation contexts.Helps in small-lot residential developments.AlterationRevisedAligned with Appendix BM’s definition for existing homes.Clarifies remodel vs. existing noncompliant conditions.Attached GarageRevisedExpanded to clarify fire separation zones and access conditions.Important for EERO and smoke alarm rules.Battery System (NEW)AddedIntroduced to support energy storage readiness requirements.Critical for PV + storage-ready homes.Detached StructureRevisedAligns definitions used in ADUs, sheds, and storage occupancies.Reduces interpretation disputes.Habitable SpaceRevisedBetter coordination with Chapter 3’s room size changes.Important for lofts, ADUs, and efficiency units.Loft (NEW)AddedSupports new Appendix BL “Tiny Houses” and loft access rules.Defines height, area, and functional limitations.MezzanineRevisedCoordinated with Chapter 5/3 restructuring.Ensures mezzanines not misused as habitable floors.Public WayRevisedClarified for residential-only enforcement; aligns with CBC.Important for egress and setbacks.PV-Ready (NEW)AddedNew definition enabling Appendix CG photovoltaic readiness requirements.Standardizes electrification-prep rules.Storage-Ready (NEW)AddedNew definition for battery energy storage readiness.Facilitates modern residential electrification.Tiny House (NEW)AddedNew term referencing Appendix BL.Establishes explicit regulatory language for tiny homes. ‍ ### Expert Commentary  -  Chapter 2 #### 1\. This is the first CRC cycle deeply aligned with electrification policy The addition of PV-ready, storage-ready, and battery-system definitions indicates big strategic moves toward an all-electric California residential sector. #### 2\. Loft and tiny house definitions prepare for a massive shift This supports: - Micro-units - ADUs - Sleeping lofts - Movable tiny homes These have exploded in adoption across California. #### 3\. Habitable space definition refinement affects minimum room dimensions This will directly impact residential designers optimizing square footage. #### 4\. Garage definition now tightly integrated with fire separation rules Important due to EV charging requirements and new battery storage contexts. # Chapter 3  -  Building Planning ### High-Impact Summary Chapter 3 in CRC 2025 is where a _lot_ of quiet but consequential surgery happened: 1. Global re-numbering & reorganization - Many sections in Chapter 3 were **renumbered and realigned** with the updated IRC structure. - Several older California-specific PV and ESS sections were **deleted and replaced** by the new model IRC sections with essentially equivalent language. 2. Updated environmental design criteria - **Wind, snow, and component & cladding tables** (R301.2 and R301.2.1 series) have updated notes, titles, and values to align with current national data. - **Topographic wind effects** simplified  -  Conditions 3 and 4 are removed. - **Seismic provisions** (R301.2.2) reorganized with new default seismic design category figures and removal of old figures & alternate charts. - **Snow load language** updated for how to determine loads. 3. Stronger seismic restraint of appliances - The old “Anchorage of water heaters” section was renamed and broadened to **“Seismic Restraint of Appliances and Equipment,”** with added language  -  meaning it’s no longer just about water heaters. 4. Fire-resistant construction & two-family dwellings tightened - Clarification added around the **assumed imaginary property line** between dwellings. - The fire-resistance/separation table now explicitly includes **accessory buildings**. - **Two-family dwelling separation** (R302.3) is fully broken into sub-sections: separation type, rating, continuity, supporting construction, vertically stacked units, and shared accessory rooms. 5. New section on fire-retardant-treated wood in Chapter 3 - **R302.15** is added (relocated from Chapter 8) to place fire-retardant-treated wood squarely in the building-planning conversation. 6. Big re-platforming of “habitability” + life-safety items - **Storm shelters**, **automatic sprinkler systems**, **smoke alarms**, **carbon-monoxide alarms**, **mezzanines**, **sleeping lofts**, **habitable attics**, and **handrails/stair geometry** are all reorganized and/or renamed. - New or expanded sections cover **sleeping lofts**, **stairways in existing buildings**, **automotive lifts**, and **private residence elevators**. 7. PV + ESS alignment with modern tech - **BIPV (building-integrated PV)** now has listing requirements and roof-access/egress rules near emergency escape and rescue openings. - ESS (battery) location rules expanded. 8. Wildfire exposure moved out to CWUIC - Section **R337** (wildfire exterior exposure) is deleted and replaced with a note directing users to the **California Wildland-Urban Interface Code (CWUIC)**. This chapter absolutely deserves its own dedicated article later (for your blog series), but here’s the structured breakdown. ### Detailed Change Table  -  Chapter 3 (Building Planning) #### 3.1 Global Chapter Reorganization & PV/ESS Alignment What ChangedPractical ImpactMany sections renumbered to match new IRC structure. PV & ESS sections removed and replaced with model code sections that say essentially the same thing.Plan checkers and designers have to get used to new numbers, but day-to-day technical requirements for PV/ESS largely stay the same – just more standardized. ‍ ## 3.2 Environmental & Structural Criteria (R301 Series) SectionTopicWhat ChangedPractical ImpactR301.2Climatic & Geographic Design CriteriaUpdated notes in Figure R301.2(2) (Ultimate Design Wind Speeds) and Figure R301.2(3) (Allowable Stress Design Ground Snow Loads). Tables for component & cladding loads and height/exposure adjustment coefficients updated.Wind and snow design values now better align with national data; designers must use updated figures and tables.R301.2.1.5Topographic wind effectsConditions 3 and 4 removed.Simplifies topographic factor application; removes edge-case complexities.R301.2.2Seismic provisionsApplicability provisions added; key figure retitled as default SDC map; older figures removed.Cleaner seismic mapping; reduces figure-hunting for SDC determination.R301.2.2.1.1Alternate determination of seismic design categoryAll figures removed from this section.Pushes designers to standardized SDC methods rather than alternative charts.R301.2.2.10Seismic Restraint of Appliances and EquipmentRenamed from “Anchorage of Water Heaters”; scope broadened; additional requirements added.Elevates seismic restraint for all appliances/equipment, not only water heaters.R301.2.3Snow loadsNew clarification added on how snow loads must be determined.Reduces ambiguity in high-elevation jurisdictions. ‍ ## 3.3 Fire-Resistant Construction & Two-Family Dwellings (R302 Series) SectionTopicWhat ChangedPractical ImpactR302Fire-Resistant ConstructionClarification added for the assumed imaginary line between dwellings and the exterior wall fire-resistance/separation table now explicitly includes accessory buildings.Clearer separation requirements for accessory buildings and detached garages; fewer “interpretation wars” in plan review.(Table in R302)Exterior walls / accessory buildingsAccessory buildings now appear in the fire-resistance/separation table.Designers must account for required ratings/separation for sheds, small shops, etc.R302.3Two-Family DwellingsCompletely restructured. Now includes: R302.3.1 Dwelling Unit Separation; R302.3.2 Fire-Resistance Rating; R302.3.3 Continuity; R302.3.4 Supporting Construction; R302.3.5 Vertically Stacked Dwelling Units; R302.3.6 Shared Accessory Rooms.Much more explicit expectations for duplex separations, especially stacked units and shared accessory rooms.R302.15Fire-retardant-treated woodNew section in Chapter 3 (relocated from Chapter 8).Keeps fire-retardant-treated wood in the same conceptual space as other planning/separation decisions. ‍ ## 3.4 Storm Shelters, Sprinklers, Smoke & CO Alarms, Habitable Spaces, Lofts (R307–R325) Ask any code questions on California Building Code (CBC 2025) changes & get instant answers with cited sections [▶ Learn How it works (1 min)](/code) What can you ask? (Sample questions) - When does the 2025 CBC take effect and what editions does it adopt? - What are the key California amendments to the IBC in CBC 2025? - How do Title 24 energy requirements change in 2025? - What accessibility changes are in Chapter 11B of CBC 2025? [Explore Melt Code](/code) SectionTopicWhat ChangedPractical ImpactR307.2Storm Shelters – ConstructionFormer R323; now a dedicated section detailing storm shelter construction.Codifies criteria for residential storm shelters – significant for high-hazard regions (tornado/wind).R309Automatic Sprinkler SystemsFormer R313. The word “Automatic” added consistently; references updated.Clarifies that we’re talking about automatic systems and harmonizes references.R310Smoke AlarmsFormer R314. New subsection R310.1.2 “Installation” added.More explicit installation criteria and locations.R311Carbon Monoxide AlarmsFormer R315. New subsection R311.1.2 “Installation” added.Parallel clarity to smoke alarms – critical for fuel-burning appliances and garages.R313.1.1BasementsFormer R305.1.1 relocated.Keeps ceiling height and related basement requirements near other habitable-space provisions.R313.1.2Habitable attics & basements in existing buildingsNew section.Gives a defined path for bringing existing attics/basements into compliance.R314MezzaninesFormer R325. Adds an exception with sleeping loft provisions.Prevents mezzanines/sleeping lofts from being misused to dodge story/area limits.R315Sleeping LoftsEntirely new section with provisions for sleeping lofts.Big for ADUs, tiny houses, micro-units – gives plan reviewers a clear standard.R316Habitable AtticsFormer R326; clarifying language added in R316.3, Story above grade plane, exception 4.Tightens how habitable attics count toward stories above grade.R317.7Automotive LiftsNew section for automotive lift installation.Important for residential garages with car lifts – defines safety expectations.R318.7.5.3NosingsFormer R311.7.5.3; adds exception for open risers where nosing projection can exceed 1 ¼".More flexibility for modern, open-riser stair design.R318.7.6Landings for stairwaysFormer R311.7.6; multiple exceptions added.More nuanced rules for landing configurations, especially in tight remodels.R318.7.9Stairways in existing buildingsNew section.Provides realistic criteria for existing stair retrofits.R318.8.3Ramps – handrails requiredSubsection on handrail height/grip/continuity removed and relocated to new R320 Handrails.Consolidates handrail rules into a dedicated section.R320HandrailsNew section (former R311.7.8) now solely for handrails.One place to look for all handrail rules.R322AccessibilityFormer R320. Adds R322.3 for care facilities requiring CBC Chapter 11B compliance.Aligns home-based care operations with accessibility rules.R323.1.1Private residence elevatorsNew section.Defines safety rules for private elevators in dwellings.R325Light, Ventilation & HeatingFormer R303. Natural light/ventilation broken into new subsections; exceptions relocated.Cleaner structure for min. light/ventilation, especially in open layouts.R325.9Passive Solar Energy CollectorsNew section; sunroom language moved into exceptions for Natural Light.Modernizes solar-gain and sunroom treatment. ‍ ## 3.5 PV, ESS & Wildfire (R329–R337) SectionTopicWhat ChangedPractical ImpactR329.3.1Solar Energy Systems – Equipment ListingsNew language requiring BIPV roof coverings and roof assemblies to be listed and labeled per UL 7103.Clarifies listing requirements as BIPV becomes more common in residential roofs.R329.6.4Roof Access & Pathways – BIPV systemsNew section addressing PV provisions at emergency escape and rescue openings.Avoids trapping occupants behind PV installations during emergencies.R330.4Energy Storage Systems – LocationsAdds new ESS location provisions.Tightens siting for batteries to reduce fire risk and conflict with egress.R337Materials & construction methods for exterior wildfire exposureSection removed and replaced with a note directing users to the new CWUIC.All wildfire exterior requirements now live in the separate California Wildland-Urban Interface Code. ‍ ### Expert Commentary  -  Chapter 3 - **This is the “everyday practice” chapter.** The renumbering, relocations, and new subsections will heavily affect **how designers read and navigate** the code, even if many technical requirements feel similar. - **ADUs, tiny homes, and micro-units are squarely in focus.** New/clarified treatment of **sleeping lofts, mezzanines, habitable attics, minimum room standards, stair exceptions, and handrail consolidation** are exactly where small-unit design lives. - **Electrification + resilience show up quietly but clearly.** New BIPV listing requirements, ESS location criteria, and seismic restraint of appliances and equipment all align with California’s long-term electrification and resilience policy. - **Wildfire has moved out to its own book (CWUIC).** The deletion of R337 and cross-reference to CWUIC is a big conceptual shift: designers must now pair CRC with CWUIC in WUI areas instead of treating wildfire as a chapter within CRC. # Chapter 4  -  Foundations Now onto the foundation side of the house. ### High-Impact Summary Chapter 4 gains **new soil/seismic clarity** and **new foundation options**, especially: 1. **Soil testing linked explicitly to [seismic design](/blogs/california-seismic-design-and-wui-code-requirements-cbc-chapter-7a) categories** - Added requirements for soil tests when SDC is **C or higher**, plus a new table cross-walking soil properties with the Unified Soil Classification System. 2. **New continuous footing requirements in higher SDCs** - New table in R403 for continuous footing requirements in **Seismic Design Categories D0, D1, D2**. 3. **Crushed stone footings for cast-in-place foundations** - Entirely new section allowing **crushed stone footings** in specific conditions. Overall, it’s about clarifying **when you need better soils data** and **how you can detail foundations in higher seismic categories**. ### Detailed Change Table  -  Chapter 4 (Foundations) SectionTopicWhat ChangedPractical ImpactR401.4Soil testsAdded language requiring additional soil-test consideration when Seismic Design Category C or greater applies. New Table R401.4.1(2): Properties of soils classified according to the Unified Soil Classification System.Ties soil investigation more directly to seismic demands. Geotech and structural folks now have a shared USCS-based reference.R403FootingsNew Table R403.1.2: Continuous Footing Requirements in Seismic Design Categories D0, D1 and D2.Provides prescriptive footing rules for higher seismic zones, reducing guesswork or ad-hoc detailing.R403.5Footings – Crushed stone footings for cast-in-place concrete foundationsNew section allowing crushed stone footings under certain conditions for cast-in-place foundations.Adds a more flexible, sometimes more constructible footing option, especially for certain soils or retrofit conditions. ‍ ### Expert Commentary  -  Chapter 4 - **More explicit geotech–seismic linkage.** The new soil-properties table and SDC C+ trigger formalize what many engineers were already doing informally: checking soil behavior carefully in meaningful seismic zones. - **Prescriptive continuous footing table is a win for small projects.** For typical one- and two-family homes in D0–D2, a well-structured prescriptive table can reduce the need for custom calc packages, especially on simpler projects. - **Crushed stone footing option is quietly powerful.** This can be very handy in **retrofits, constrained sites, or where drainage and constructability** are concerns  -  provided detailing is followed carefully. # Chapter 5  -  Floors ### High-Impact Summary CRC Chapter 5 receives _meaningful structural and moisture-control updates_ aligned with the new IRC and California’s seismic realities: #### 1\. New deck load criteria & guard forces Deck live loads and lateral forces have been updated to match current structural engineering practice. Deck failures were a major national issue → new rules address that. #### 2\. Joist/beam lateral restraint clarifications New relocations and renumbering clean up the long-confusing provisions for lateral restraint of joists/beams. #### 3\. New prescriptive information for post-tensioned slabs A new subsection explicitly allows **flat unbonded post-tensioned slabs** in residential floors under certain detailing conditions. This is a **big** shift for CA multi-family and podium-style construction. #### 4\. Vapor retarders aligned with Chapter 7 Sections on vapor retarders moved/renumbered to match the fully revamped moisture chapters. #### 5\. Blocking, bridging, and fire-blocking reorganized Provides clearer installation criteria for floor assemblies. ### Detailed Change Table  -  Chapter 5 SectionTopicWhat ChangedPractical ImpactR502.7 & R502.7.1Lateral restraint of joists & beamsSubsections reorganized and renumbered to clarify joist lateral bracing and blocking requirements.Eliminates inspector disagreements; ensures consistent lateral restraint to prevent roll-over failures.R502.14Cutting, drilling, and notchingUpdated language consistent with roof and wall framing changes.Prevents oversizing of field modifications, especially for engineered lumber.R505.2.1–R505.3Cold-formed steel floor framingRelocated from R505.1.2; reorganized for clarity.Improves navigation for residential CFS designers.R506.3Vapor retardersRenumbered from R506.2. Removal of outdated language; referenced back to reworked Chapter 7 WRB/Vapor sections.Aligns floor vapor barriers with whole-building moisture strategy.R507 (General)Exterior decksMajor reorganization. Section numbering updated; tables relocated.Sets the stage for updated structural deck criteria below.R507.3Live loads on decksLanguage updated for load path clarity.Improves structural reliability of deck framing.R507.9Vertical & lateral supportsNumerous changes clarifying deck column loads and diagonal bracing.Leads to fewer deck collapses by ensuring proper support.R507.10Vertical & lateral forcesRevised connection rules; text restructured.Aligns with current best practices for resisting deck lateral movement.R507.11GuardsUpdated language referring to Table R301.5 guard loading.Makes guard load criteria consistent across floors, decks, porches.R507.13Vertical & lateral supports at deck postsConsolidates older fragmented criteria into a single cohesive rule.Reduces conflict between inspectors, designers, and installers.R506.2.2Flat unbonded post-tension slabs (NEW)New subsection allowing flat unbonded PT slabs with specific detailing: minimum thickness, tendon spacing, cover, inspection requirements.Opens the door to using PT slabs in CRC scopes, benefiting ADUs, additions, garages, and small multifamily podiums.R506.5Ground supported slabs & membranesUpdated membrane & moisture barrier criteria.Ensures better slab-on-grade moisture performance. ‍ ### Expert Commentary  -  Chapter 5 #### Decks are a major focus  -  expect strict enforcement. California AHJs (Bay Area, LA, San Diego) already emphasize deck safety heavily. CRC 2025 codifies: - clearer vertical load rules - new lateral load requirements - updated guard load criteria This will significantly reduce catastrophic deck failures. #### Post-tension slabs in the CRC is a big break from tradition. Prior cycles relied heavily on engineer-of-record judgement. CRC 2025 finally acknowledges **flat unbonded PT** as mainstream in small residential. Perfect for: - ADUs - Garage-top decks - Small multifamily - Hillside foundations #### Vapor retarder realignment avoids contradictions. Chapter 7 changes forced this; now all vapor-control rules match the redesigned residential wall/roof assemblies. # Chapter 6  -  Wall Construction #### High-Impact Summary Chapter 6 sees MAJOR updates  -  some structural, some moisture-control, some energy/performance: #### 1\. New application provisions for sheathing & braced wall lines All of section **R602** gets renumbered and reorganized. #### 2\. New braced-wall rules (R602.10) aligned with 2024 IRC California retains seismic-critical bracing rules but reorganizes the entire section: - New figure references - New table numbering - Clarified bracing methods (let-in bracing, wood structural panels, gypsum board bracing, etc.) - Updated hold-down detailing #### 3\. New continuous sheathing requirements Seismic areas now require: - Specific nail patterns - Edge fastening - Panel blocking #### 4\. Vapor barriers, WRBs, and exterior insulation integrated with Chapter 7 This is one of the most _cross-referenced_ areas in the CRC. #### 5\. Fire blocking and draft stopping reorganized New subsections added for clarity. #### 6\. Revised requirements for multi-panel headers & built-up beams Coordination with new structural NDS references. ### Detailed Change Table  -  Chapter 6 SectionTopicWhat ChangedImpactR602 (General)Wall constructionMany subsection numbers changed throughout wall framing provisions.Designers/inspectors must carefully track new numbering.R602.1.2Lumber gradeClarifies SDR (stress design rating) application.Cleaner structural design for dimensional lumber.R602.3.5ContinuityContinuous top plate provisions clarified; new exceptions added.Helps with irregular framing, vaulted ceilings, and complex roofs.R602.3.7–R602.3.8Header sizes & multi-member headersUpdated values; header spans revised to match current structural practice.Allows smarter sizing for energy efficiency (less thermal bridging).R602.5Multi-panel wall sheathingNew provisions controlling panel stacking, blocking, and shear transfer.Improves lateral performance in seismic regions.R602.7 (and subsections)Sill, sole, and plate anchorageClarified anchorage requirements with updated spacing values.Reduces sill-plate uplift failures in seismic events.R602.7.5Alternate anchorageNew section allowing alternate anchorage with engineered values.Encourages performance-based or engineered anchorage solutions.R602.8 (Draft-stopping & fire-blocking)Fire blocking reorganizedClearer categories of concealed spaces; renumbered subsections.Reduces misinterpretation — very important in multi-story townhouses.R602.10 (Braced Wall Lines)Entire section significantly revisedNew bracing method designations; new table references; figure numbering updated.Designers must relearn numbering and table structure.R602.10.5–10.6Wood structural panel bracingRewritten to include updated nailing patterns and blocking requirements.Improves seismic shear wall reliability.R602.10.12Drilling & notching of braced wall panelsNew language controls field perforations.Prevents reduction of shear capacity during field modifications.R602.11Hold-downsUpdated to reference new uplift and shear capacities from wall bracing tables.Stronger anchorage; fewer overturning failures.R603–R606Cold-formed steel, masonry, concreteSection numbering updated; wording clarified.Cleanup edits; no major substantive change.R608–R613Structural insulated panels (SIPs) & ICFRenumbered and cross-references corrected.Aligns SIP/ICF rules with envelope changes in Chapter 7. ‍ ### Expert Commentary  -  Chapter 6 #### 1\. The bracing section (R602.10) is the beating heart of residential seismic performance. CRC 2025’s reorganized tables and figures align with the 2024 IRC but retain California’s stricter stance. Result: **Better clarity + same high safety bar.** #### 2\. Continuous sheathing provisions significantly enhance seismic life safety. These changes harden residential wood structures against: - soft-story collapse - edge-nail withdrawal - uplift failures #### 3\. Blocking and fire-blocking cleanup prevents massive field inspection friction. The 2022 code had overlapping categories and confusing exceptions; CRC 2025 is much cleaner. #### 4\. The header update is energy-performance relevant. Smaller headers = less thermal bridging = easier HERS compliance. #### 5\. The new integration with Chapter 7 (moisture) is crucial. Exterior insulation and continuous WRBs are now deeply tied to wall construction. CRC wall assemblies now anticipate: - CI (continuous insulation) - vapor-open assemblies - multi-layer WRB systems Fully aligned with modern building Science. ‍ # Chapter 7  -  Wall Covering ### High-Impact Summary CRC Chapter 7 has been **extensively reorganized** to reflect modern building science and envelope design: #### 1\. Entire Water-Resistive Barrier (WRB) system restructured - The chapter now clearly separates **WRB products**, **installation**, **drainage requirements**, and **compatibility with exterior insulation**. - Multiple subsections were deleted, renumbered, or rewritten for clarity. #### 2\. Vapor retarder requirements revamped - Aligns with the rewritten building-envelope sections in Chapter 6 & Chapter 5. - Introduces new Class I/II/III VR clarifications for mixed-dry climates. #### 3\. Exterior plaster (stucco) drainage plane clarified - New classification rules determine when stucco must have a **drainage gap**. - Removes old language about moisture barriers and replaces with drainage-specific rules. #### 4\. Integration with exterior insulation - New WRB + rigid foam + cladding pathways reflect modern continuous insulation assemblies. #### 5\. Siding, manufactured stone, and veneer rules reorganized - All of Section R703 is renumbered. - New clarity on flashing, weeps, and fastening requirements. ### Detailed Change Table  -  Chapter 7 (Wall Covering) SectionTopicWhat ChangedPractical ImpactR702 (General)Chapter StructureMany subsection numbers changed; language reorganized for clarity.Requires careful renumber navigation for all WRB/vapor-control references.R702.1.2Water-Resistive BarriersCompletely rewritten: WRB materials + performance + installation structured in new format.Eliminates years of confusion between ASTM standards, drainage gaps, and multi-layer WRB requirements.R702.1.2.1WRB – InstallationUpdated installation requirements; removed duplicate language.Reduces conflict between inspectors and installers, especially on multi-WRB systems.R702.1.2.2 (NEW)Drainage RequirementsNew drainage requirements based on WRB class and cladding type.Big for stucco, adhered stone, and other reservoir claddings prone to trapping moisture.R702.1.3Vapor RetardersHeavily updated; renumbered; aligned with modern vapor control science and climate-dependent rules.Helps prevent inward vapor drive issues and mold failures.R702.4–R702.7Exterior Coverings (Siding, Stone, Veneer)Large structural reorganization of siding, lath, and plaster subsections.Matching IRC structure makes future transitions easier and clearer for installers.R703 (General)Exterior CoveringsAll numbering changed. Many provisions rewritten or relocated.Plan reviewers and designers must update all cross-references in standard sheets.R703.2FlashingExpanded clarity on required flashing types and locations.Helps reduce water intrusion failures in fenestration + ledger interfaces.R703.3Siding MaterialsNew material-specific rules (wood, fiber cement, vinyl, polypropylene).Improves compliance for modern cladding systems.R703.7Exterior Plaster (Stucco)Language reorganized; drainage rules updated; water barrier notes removed.Aligns CA stucco with national best practice for drainage and drying.R703.9Adhered Masonry VeneerUpdated installation + WRB + flashing criteria.Reduces trapped moisture and façade failures. ‍ ### Expert Commentary  -  Chapter 7 #### 1\. This is the largest envelope change since CRC became code. The reorganized WRB + drainage + vapor control framework solves major California problems: - stucco failures - reverse vapor drive - unvented cladding moisture buildup - competing WRB layers #### 2\. WRBs and vapor retarders are now aligned with building science. California’s climate zones (especially Zones 2–10) are prone to _inward vapor drive_ issues. This rewrite brings the CRC closer to the building-science approach used in high-performance structures. #### 3\. Exterior insulation compatibility rules reflect statewide electrification. As more homes electrify, CI (continuous insulation) becomes standard → CRC 2025 now anticipates this. #### 4\. Stucco drainage gap rules are a critical update. Reservoir claddings like stucco hold water → CRC now requires drainage depending on climate zone & WRB type. #### 5\. Siding and veneer reorganization improves reliability. Manufactured stone veneer failures used to be widespread  -  these new rules cut failure risk dramatically. ‍ # Chapter 8  -  Roof-Ceiling Construction #### High-Impact Summary Chapter 8 includes structural, fire-resistance, ventilation, and insulation-related changes: #### 1\. Moisture & vapor control in attics updated - New rules align attic moisture management with Chapter 7 WRB rules. #### 2\. New provisions for unvented attic assemblies - Updated language and relocation of subsections. - New cross-references to mechanical dehumidification and continuous insulation. #### 3\. Clarified ceiling height & insulation requirements - Aligns with the reorganized habitable-space sections in Chapter 3. #### 4\. Revised roof sheathing & fastening rules - Reinforces uplift resistance for high-wind zones. #### 5\. Updated roof / attic ventilation ratios - Vent area ratios updated for improved moisture control. #### 6\. Radiant barriers reorganized Cleaned-up location, detailing, and installation rules. ‍ ### Detailed Change Table  -  Chapter 8 SectionTopicWhat ChangedPractical ImpactR801–R802 (General)Chapter structureMany subsections renumbered across roof/ceiling framing.Designers & builders must use updated references.R802.2Design & constructionClarified alternative provisions for engineered roofs.Cleaner coordination with manufacturers & engineers.R802.4RaftersClarified notch/cut rules consistent with Chapter 5.Reduces structural weakening in field cuts.R802.11Roof Uplift ResistanceRevised rules; uplift connections now more explicit and aligned with wind maps.Better high-wind protection.R803–R803.2Roof SheathingUpdated fastening patterns; clarified spans and layout.Prevents sheathing blow-off in extreme weather.R806 (General)Roof VentilationClarified installation & vent location; harmonized with new moisture-control rules.Improves attic drying and roof longevity.R806.2Minimum Vent AreaNew ratios added; exceptions reorganized.Improves moisture control & reduces condensation failures.R806.5Unvented Attic AssembliesSignificantly revised; clarifies CI + air-impermeable insulation pathways.Allows more modern roof assemblies and supports net-zero-ready homes.R807Attic AccessClarified access sizing and placement.Improves accessibility for equipment and inspections.R808Radiant BarriersSection moved & rewritten for clarity.Cleaner installation criteria; fewer inspection conflicts. ‍ ### Expert Commentary  -  Chapter 8 #### 1\. Unvented attic rules are vastly improved  -  perfect for heat pumps + PV homes. CRC now recognizes modern assemblies that rely on: - exterior rigid insulation - interior air-impermeable spray foam - hybrid assemblies - continuous exterior insulation over the roof deck Essential for California electrification goals. #### 2\. Roof uplift resistance improvements respond to climate change. Atmospheric river wind events + wildfire-driven windstorms → CRC now includes stronger uplift rules. #### 3\. Attic ventilation ratio updates reflect new research. California climate zones historically saw: - mold issues - sheathing rot - condensation failures These new ratios + better WRB connections reduce these failures. #### 4\. Roof sheathing fastening clarifications reduce field disputes. This positively affects production builders and custom homebuilders alike. ‍ # Chapter 9  -  Roof Assemblies ### High-Impact Summary CRC 2025’s Chapter 9 introduces **major updates** impacting roofing performance, moisture management, wind resistance, and installation standards: #### 1\. Roof-covering classification & compliance sections reorganized - Sections R902–R907 are renamed, renumbered, and rewritten for clarity. - Several cross-references updated to align with exterior fire rating, PV/BIPV, and energy sections. #### 2\. Underlayment & fastening rules updated for high-wind regions Tables and exceptions revised to match modern ASCE wind data and CA-specific wind zones. #### 3\. Asphalt shingles installation modernized New section numbers and clearer attachment rules. #### 4\. Clay and concrete tile roofing updated - Attachment requirements clarified, - Wind uplift criteria more explicit. #### 5\. Wood shingle/shake roofing provisions reorganized New numbering and clarified fastening rules. #### 6\. Metal roof coverings reorganized Provides standardized installation language and performance references. #### 7\. Roof flashing requirements updated Expanded to ensure compatibility with WRBs and stucco drainage changes from Chapter 7. #### 8\. BIPV references modernized BIPV roof coverings must now meet updated UL listing and labeling requirements discussed earlier in Chapter 3. This chapter is one of the most important for contractors, roofing designers, AHJs, and anyone involved in reroofing or new construction. ### Detailed Change Table  -  Chapter 9 (Roof Assemblies) SectionTopicWhat ChangedPractical ImpactR902–R907 (General)Global ReorganizationSignificant renumbering across roof covering classifications & requirements.Requires re-referencing and updated plan templates.R905 (General)Roof CoveringsSection numbering updated to match new IRC organization.Simplifies cross-referencing with national standards.R905.1.1UnderlaymentUnderlayment rules updated; references and footnotes reorganized.Better alignment with modern synthetic and self-adhered membranes.R905.1.2–1.3FastenersClarified fastening requirements for various underlayments.More reliable wind-uplift performance.R905.2Asphalt ShinglesNumbering reorganized and clarifications added for installation, wind resistance, and attachment.More consistent enforcement and reduced installation errors.R905.3Clay & Concrete TileRevised fastening rules and uplift testing references.Critical for CA high-wind + wildfire zones.R905.4Metal ShinglesUpdated installation language.Improves durability for metal roof systems.R905.5–R905.9Metal Panels & Specialty RoofsAll renumbered; language modernized.Ensures compatibility with WRBs and new flashing rules.R905.10Thermoplastic/Elastomeric RoofsClarified application rules for low-slope residential roofs.Aligns with current roofing manufacturer standards.R905.11Wood Shakes/ShinglesUpdated fastening rules and fire-treatment references.Reduces risk in wildfire-prone regions.R906Roof FlashingExpanded flashing rules, now fully aligned with Chapter 7 drainage/WRB requirements.Major improvement for moisture management.R907ReroofingClarifies tear-off requirements and exceptions.Provides stronger guidance for reroofing inspections. ‍ ### Expert Commentary  -  Chapter 9 #### 1\. Underlayment changes are a quiet but massive shift Modern synthetic underlayments behave differently from felt. CRC adjusts installation, laps, and fastening accordingly. #### 2\. Flashing updates align roofing with wall-envelope science With Chapter 7’s drainage overhaul, roof-wall interfaces must also drain correctly → this change is critical to stopping water intrusion. #### 3\. Tile roofs get needed wind-resistance improvements Given CA’s atmospheric river storms and foothill wind exposure, better tile attachment rules matter. #### 4\. Re-roofing clarifications reduce inspection ambiguity Previously, reroof triggers and overlays produced inconsistent interpretations across jurisdictions. ‍ # Chapter 10  -  Chimneys & Fireplaces Chapter 10 changes are less voluminous but still meaningful, especially for safety, ventilation, and installation components. ### High-Impact Summary #### 1\. Flue sizing tables updated & renumbered Chapter 10 reorganizes its flue sizing and installation rules for clarity. #### 2\. Masonry chimney height & reinforcement clarified New details improve resistance to high winds and seismic conditions. #### 3\. Factory-built fireplace rules retitled & updated Sections retitled for clarity; manufacturer listing requirements modernized. #### 4\. Spark arrestor rules reaffirmed Improved clarity for wildfire-prone areas. #### 5\. Expansion of mechanical fireplace provisions Better alignment with modern closed-combustion fireplaces and gas units. ### Detailed Change Table  -  Chapter 10 SectionTopicWhat ChangedImpactR1001Masonry Fireplaces & ChimneysUpdated wording for seismic + wind reinforcement and chimney extension requirements.Improves safety in high-wind and seismic areas.R1002Factory-Built FireplacesRetitled; subsections renumbered.More intuitive structure for installers and AHJs.R1003Fireplace Stoves & Room HeatersTerminology updated; listing requirements modernized.Ensures compatibility with clean-combustion appliances.R1004Gas FireplacesClarifies installation, venting, and combustion-air rules.Prevents improper vent-less/gas installations.R1005Chimney ClearancesClarifies clearance-to-combustibles and termination heights.Better fire safety and draft performance.R1006Flue SizingTables reorganized; clarity improvements added.Reduces sizing errors.R1007Spark ArrestorsWording updated.Supports fire-safety in WUI areas. ‍ ### Expert Commentary  -  Chapter 10 #### 1\. Seismic reinforcement rules matter deeply in CA Older chimneys often collapse during earthquakes. CRC 2025 clarifies reinforcement & anchorage rules to mitigate this. #### 2\. Factory-built fireplaces are now easier to interpret Renamed subsections and cleaner structure reduce confusion. #### 3\. Spark arrestors: California wildfire realities With intense WUI risk, fireplace spark control is essential  -  updated rules reflect this priority. ‍ # Chapter 11  -  Energy Efficiency CRC Chapter 11 simply **cross-references** the **California Energy Code (Title 24, Part 6)**. ### High-Impact Summary #### 1\. Entire chapter is unchanged in CRC 2025 #### 2\. CRC 11 continues to defer fully to the Energy Code All energy rules for: - insulation - fenestration - HVAC - envelope tightness - PV + battery readiness - whole-building electrification …are governed by the **CEC**, not the CRC. #### 3\. The Energy Code (T24 Part 6) carries the load CRC does not attempt to duplicate energy standards  -  it simply points designers to the [Energy Code](/blogs/understanding-title-24-a-guide-to-the-california-building-codes-cbc-crc-energy-code). #### 4\. Energy Code 2025 is heavily electrification-focused Although _outside_ CRC, this is crucial for your Melt Code + Melt Plan messaging. Expect stricter: - heat pump requirements - PV + storage readiness (aligned with CRC Appendix CG) - envelope tightening - heat pump water heaters - demand flexibility / load shifting requirements # Appendix Bl  -  Tiny Houses The IRC Appendix Q for Tiny Houses has been **adopted and expanded in California** as **Appendix BL**, with California-specific modifications. Tiny houses now have a complete regulatory structure for: - ceiling heights - lofts - stairs, ladders, alternating tread devices - emergency escape & rescue openings (EEROs) - mezzanines vs lofts - guards - smoke/CO alarms This is critical for ADUs, micro-units, movable tiny homes, and compact infill housing. ### High-Impact Summary  -  Appendix BL #### 1\. Tiny House Definition + Scope established Appendix BL establishes tiny houses as **permanent dwellings** under CRC, separate from RV/MH/park models. #### 2\. Minimum ceiling heights defined - **6 ft 8 in** in habitable spaces - **6 ft 4 in** in bathrooms - **3 ft** minimum in lofts (same as CBC Appendix P sleeping lofts) #### 3\. Loft rules are fully codified Tiny house lofts now have: - maximum 70 ft² limits, - minimum 5 ft dimension, - 3 ft minimum clear height over 50% of floor area, - guard requirements, and - mandatory smoke alarms. #### 4\. New access/egress rules for lofts Approved methods include: - stairs, - ship ladders, - alternating tread devices, - ladders (meeting specific geometry). #### 5\. Emergency Escape & Rescue Openings required Every sleeping loft must: - open directly to an EERO **or** - have an opening into a room with an EERO. #### 6\. Smoke + CO alarms in lofts required Interconnected alarms required  -  battery backup allowed. #### 7\. Guards for loft edges & open sides Must meet CRC guard requirements but allow more flexible designs suited for micro-units. #### 8\. Heating, ventilation & energy requirements remain same as full dwellings No reduction or alternative provisions  -  tiny houses must meet: - mechanical ventilation requirements (fan/ERV/HRV) and - CA Energy Code (Title 24, Part 6) requirements. ### Detailed Change Table  -  Appendix BL (Tiny Houses) SectionTopicWhat ChangedImpactBL101ScopeEstablishes Appendix BL for tiny houses as permanent dwellings.This formally legalizes tiny houses under CRC.BL102DefinitionsAdds new definitions: tiny house, loft, landing, ships ladder, alternating tread device.Clear terminology for plan review & construction.BL103.1Minimum Floor AreaTiny houses are exempt from the 120 ft² minimum room-area requirements.Allows ultra-compact units.BL103.2Ceiling HeightMinimum ceiling heights established for habitable rooms, bathrooms, and lofts.Avoids unsafe low clearance conditions.BL104.1–104.4LoftsNew rules for loft area, dimensions, clear height, and guard requirements.Framework for safe, functional sleeping lofts.BL105Loft AccessAdds allowable access methods including ladders and ATDs.Supports flexible tiny house designs.BL106Loft EERODefines emergency escape & rescue requirements for lofts.Fire safety for upper sleeping platforms.BL107Smoke/CO AlarmsSmoke alarms required in lofts; coordinated with CRC Ch. 3 alarm rules.Essential life-safety measure. ‍ ### Expert Commentary  -  Appendix BL #### California now has one of the clearest tiny house regulations in the U.S. Appendix BL, paired with CBC Appendix P (sleeping lofts), gives California designers: - predictable review requirements - clear loft + stair criteria - unambiguous sizing and egress standards This will massively accelerate: - ADU development - small-lot micro-units - missing-middle housing - student housing cabins - transitional housing # Appendix Bm  -  Existing Buildings (Residential) ### High-Impact Summary  -  Appendix BM Appendix BM creates a **residential-only** counterpart to the CBC Existing Building Code. It enables: - simplified compliance for remodels, additions, alterations - clear exceptions for existing stairs, ceiling heights, landing sizes - special allowances for older homes - pathways for meeting fire, structural, and egress requirements in constrained existing conditions This is HUGE for: - ADU conversions - garage conversions - attic & basement conversions - older homes built before modern codes ### Detailed Change Table  -  Appendix BM SectionTopicWhat ChangedImpactBM101ScopeAppendix BM created for existing residential buildings.Establishes dedicated regulatory framework for remodels.BM103–BM108Alterations & RepairsRules for alterations, repairs, additions defined.Clarifies when existing conditions can remain unchanged.BM110Means of EgressStairways, handrails, landing sizes get exceptions for existing buildings.Major benefit for older homes where strict CRC geometry is impossible.BM111Fire ProtectionClarifies when sprinklers, alarms, and fire separations are required during remodels.Balances life safety with feasibility.BM112StructuralExisting structural systems allowed to remain with engineering justification.Essential for retrofit projects.BM113EnergyExisting buildings can comply using tailored options but must meet minimum envelope criteria.Addresses retrofit realities. ‍ ### Expert Commentary  -  Appendix BM #### Massive win for renovation, ADUs, and conversion projects. This appendix reduces contradictions between CRC and retrofit projects by: - providing legal pathways for “existing nonconforming” features - allowing alternative compliance - allowing existing stairs & dimensions to remain in many cases It dramatically reduces cost + permitting friction for older CA housing stock. # Appendix Bn  -  Relocated Buildings ### High-Impact Summary Appendix BN governs situations like: - Moving an older house to a new lot - Relocating homes in wildfire rebuild zones - Temporary relocation for construction It ensures transported buildings meet **minimum structural, fire, sanitation, energy, and anchorage requirements**. ### Detailed Change Table  -  Appendix BN SectionTopicWhat ChangedImpactBN101ScopeEstablishes regulations for moved dwellings & relocated structures.Provides legal clarity for relocations.BN103–BN107Structural, Fire, SanitationSets minimum compliance for structure, fire safety, plumbing, mechanical, and electrical.Ensures relocated homes are safe upon reinstallation.BN108FoundationsRequires relocated buildings to sit on foundations meeting current CRC Chapter 4.Prevents unsafe installations. ‍ ### Expert Commentary  -  Appendix BN #### Relocated buildings were previously a gray zone. Now there is a: - clear safety baseline - clear retrofit expectation - clear foundation standard - clear electrical & plumbing connection requirement Very important for fire-rebuild projects, seismic relocation programs, and reuse of historic structures. # APPENDIX CG  -  PV-READY & ENERGY STORAGE-READY HOMES ### (Electrification-focused  -  extremely important for CA policy) Appendix CG contains requirements to make new homes: #### 1\. PV-ready (solar-ready) #### 2\. Energy storage-ready (battery-ready) #### 3\. Electrification-ready ### High-Impact Summary  -  Appendix CG #### 1\. Mandatory dedicated space for future PV system components - Panelboard space - Roof space allocation - Conduit pathways #### 2\. Dedicated raceways for PV + battery - Raceways from roof to panel location - No bends tighter than code allows - Labeling & accessibility required #### 3\. Load center capacity & reserved breaker space - Ensures panelboards can accept future PV backfeed + battery inverters. #### 4\. Storage-ready requirements for energy storage systems - Minimum wall space - Working clearances - ESS-ready circuit requirements - Ventilation/clearance notes #### 5\. Coordination with Chapter 3 (PV location restrictions) No PV allowed to obstruct emergency rescue openings. ### Detailed Change Table  -  Appendix CG SectionTopicWhat ChangedImpactCG101ScopeEstablishes PV-ready & Storage-ready requirements.Supports California’s electrification goals.CG201GeneralApplies to new homes, additions, and major remodels meeting certain thresholds.Ensures future-proofing.CG301Solar ZoneDefines required solar-ready roof area.Ensures homes are PV-capable.CG302Interconnection PathwaysConduit/raceway requirements.Simplifies future PV installation.CG401–CG402Battery-ReadyWall space, clearances, pathways for ESS.Prepares homes for energy storage additions.CG501Electrical Panel RequirementsBackfeed capacity and reserved breaker space.Reduces costly panel upgrades later. ‍ ### Expert Commentary  -  Appendix CG #### This appendix is part of California’s electrification architecture. Homes built today must be ready for: - PV - Batteries - EV chargers - Heat pumps - Demand-response systems Appendix CG provides the physical layout & routing framework that makes future retrofit seamless. # FAQs ### 1\. What are the biggest changes in the 2025 California Residential Code? The 2025 CRC reorganizes major chapters, expands life-safety rules, revamps the building envelope, modernizes decks and structural rules, and adds new appendices for tiny houses, existing buildings, relocated dwellings, and PV/battery-ready homes. ### 2\. When does the 2025 CRC take effect? The 2025 California Residential Code becomes mandatory statewide on **January 1, 2026**, unless a local jurisdiction adopts it earlier. ### 3\. What new appendices were added in the 2025 CRC? Four major appendices were added: - Appendix BL  -  Tiny Houses - Appendix BM  -  Existing Buildings - Appendix BN  -  Relocated Dwellings - Appendix CG  -  PV + Storage Ready Homes ### 4\. Does the 2025 CRC apply to ADUs? Yes. ADUs must comply with the CRC unless exempted by state ADU law. New changes to lofts, egress, alarms, and existing-building pathways directly affect ADU projects. ### 5\. What are the new seismic requirements in the 2025 CRC? Updated SDC maps, revised seismic appliance anchorage, new prescriptive footings for SDC D0–D2, and new soil investigation rules for SDC C or higher. ### 6\. Did wind or snow design loads change in CRC 2025? Yes. Wind and snow figures were replaced with updated national data, and the topographic wind effect rules were simplified. ### 7\. Are there new requirements for two-family dwellings? Yes. Duplex separation rules were completely restructured with new subsections covering rating, continuity, stacked units, and shared accessory rooms. ### 8\. What changed for residential decks in the 2025 CRC? Deck loads, lateral bracing, guard forces, vertical supports, and connection rules were all updated - addressing nationwide deck failures. ### 9\. What are the new rules for sleeping lofts? The CRC now includes fully codified rules for loft size, height, guards, access, and emergency escape openings. ### 10\. Did stair geometry rules change? Yes. Handrails moved to a new section, landing exceptions expanded, and new provisions were added for stairs in existing buildings. ### 11\. What changed in CRC Chapter 7 for moisture protection? WRBs were completely restructured, drainage requirements added, stucco moisture-barrier language rewritten, and vapor-retarder rules modernized. ### 12\. Are there new requirements for stucco drainage? Yes. Reservoir claddings like stucco now require drainage based on WRB class and climate zone. ### 13\. What are the new roof ventilation rules? Chapter 8 updates vent ratios, consolidates vent location rules, and aligns unvented attic assemblies with exterior insulation and mechanical systems. ### 14\. Did roof sheathing fastening rules change? Yes. Sheathing patterns were revised for high-wind uplift resistance and better moisture control. ### 15\. How did roof underlayment rules change in 2025? Underlayment fasteners, laps, and installation methods were updated to reflect modern synthetic membranes and higher wind loads. ### 16\. Are there new rules for tile or metal roofs? Yes. Fastening, uplift resistance, and installation rules were modernized for clay tile, concrete tile, metal shingles, and metal panels. ### 17\. What changed for reroofing? Reroofing requirements were clarified, especially regarding when tear-offs are mandatory versus when overlays are acceptable. ### 18\. Are wildfire requirements still in Chapter 3? No. Section R337 was removed. Wildfire exterior rules now appear in the **California Wildland-Urban Interface Code (CWUIC)**. ### 19\. Did chimney or fireplace rules change? Yes. Chimney reinforcement, clearances, spark arrestors, and gas-fireplace combustion-air rules were clarified. ### 20\. What does PV-ready mean in the 2025 CRC? It means the home must include: - A solar-ready roof zone - Conduit or raceways from roof to panel - Panelboard space for future PV breakers ### 21\. What does storage-ready mean? Homes must be built with: - Wall space for a battery system - Pathways for wiring - Reserved panelboard capacity - Safety clearances ### 22\. Does every new home in CA need to be storage-ready? Yes, under Appendix CG, most new residential buildings must be designed for future battery installation. ### 23\. Are tiny houses legal under the 2025 CRC? Yes. Appendix BL formalizes tiny houses as permanent dwellings, with detailed rules for ceiling heights, lofts, access, alarms, and EERO. ### 24\. How does Appendix BM affect remodels? It creates alternative compliance paths for existing buildings, allowing older stairs, ceiling heights, and structural systems to remain when safe. ### 25\. How does Appendix BN affect relocated homes? It establishes minimum structural, fire, sanitation, and anchorage requirements for moved or relocated homes. ‍ ### More California Building Code Guides - [Permits & AmendmentsThe California Building Permit Process Explained: From Plan Check to Certificate of Occupancy](/blogs/the-california-building-permit-process-explained-from-plan-check-to-certificate-of-occupancy) - [Energy Code (IECC)Understanding Title 24: A Guide to the California Building Codes (CBC, CRC & Energy Code)](/blogs/understanding-title-24-a-guide-to-the-california-building-codes-cbc-crc-energy-code) - [Overview GuideA Practitioner's Guide to California's MEP, Energy (Title 24), and CALGreen Codes](/blogs/a-practitioner-s-guide-to-california-s-mep-energy-title-24-and-calgreen-codes) - [Residential Code (IRC)Applying the California Residential Code (CRC): Stairs, Decks, ADUs, and Remodels](/blogs/applying-the-california-residential-code-crc-stairs-decks-adus-and-remodels) - [Accessibility (ADA)California Accessibility Code: Navigating CBC Chapter 11A, 11B, and ADA Conflicts](/blogs/california-accessibility-code-navigating-cbc-chapter-11a-11b-and-ada-conflicts) --- This blog is powered by Superblog. 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