The 2025 California Residential Code (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

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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

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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

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3.2 Environmental & Structural Criteria (R301 Series)

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3.3 Fire-Resistant Construction & Two-Family Dwellings (R302 Series)

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3.4 Storm Shelters, Sprinklers, Smoke & CO Alarms, Habitable Spaces, Lofts (R307–R325)

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3.5 PV, ESS & Wildfire (R329–R337)

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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 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)

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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

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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

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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.

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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)

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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.

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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.

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Detailed Change Table  -  Chapter 8

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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.

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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)

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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.

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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

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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.

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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.

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)

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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

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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

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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

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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.

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