Chapter 16.05 — CALIFORNIA MECHANICAL CODE, CALIFORNIA CODE OF

REGULATIONS, TITLE 24, PART 4*

Sections:

16.05.010 2025 California Mechanical Code, Title 24, Part 4 adopted and amended.

• Editor’s Note: Prior ordinance history: Ordinance Nos. 5565 and 5666.

16.05.010 2025 California Mechanical Code, Title 24, Part 4 adopted and amended.

The California Mechanical Code, 2025 Edition, Title 24, Part 4 of the California Code of Regulations together with those omissions, amendments, exceptions and additions thereto, is adopted and hereby incorporated in this chapter by reference and made a part hereof the same as if fully set forth herein.

Unless superseded and expressly repealed, references in City of Palo Alto forms, documents and regulations to the chapters and sections of the former editions of the California Code of Regulations, Title 24 shall be construed to apply to the corresponding provisions contained within the California Code of Regulations, Title 24, 2025. Ordinance No. 5565 of the City of Palo Alto and all other ordinances or parts of ordinances in conflict herewith are hereby suspended and expressly repealed.

Wherever the phrases "California Mechanical Code" or "Mechanical Code" are used in this code or any ordinance of the City, such phrases shall be deemed and construed to refer and apply to the California Mechanical Code, 2025 Edition, Title 24, Part 4 of the California Code of Regulations, as adopted by this chapter.

One copy of the California Mechanical Code, 2025 Edition, has been filed for use and examination of the public in the Office of the Building Official of the City of Palo Alto.

(Ord. 5675 § 1 (part), 2025)

The provisions of this chapter contain cross-references to the provisions of the California Mechanical Code, 2025 Edition, in order to facilitate reference and comparison to those provisions.

(Ord. 5675 § 1 (part), 2025)

The provisions of this chapter shall constitute local amendments to the cross-referenced provisions of the California Mechanical Code, 2025 Edition, and shall be deemed to replace the cross-referenced sections of said Code with the respective provisions set forth in this chapter.

(Ord. 5675 § 1 (part), 2025)

Administration and enforcement of this code shall be governed by Chapter 1, Division II of the 2025 California Building Code as amended by Palo Alto Municipal Code Chapter 16.04.

(Ord. 5675 § 1 (part), 2025)

Chapter 1, Division II Administration of the 2025 California Mechanical Code is adopted by the City of Palo Alto to supplement, to the extent it does not conflict with, Chapter 1, Division II of the 2025 California Building Code, as amended.

(Ord. 5675 § 1 (part), 2025)

The following Appendix Chapters of the California Mechanical Code, 2025 Edition, are adopted and hereby incorporated in this chapter by reference and made a part hereof the same as if fully set forth herein:

A. Appendix B – Procedures to be followed to place gas equipment in operation.

B. Appendix C – Installation and testing of oil (liquid) fuel-fired equipment.

( Ord. 5675 § 1 (part), 2025)

Subdivision (6) of Section 104.2 of Chapter 1 of the California Mechanical Code is added to read:

(6) ADDITIONAL EXCEPTIONS: Reference Mechanical Section under PAMC 16.04.110 Section 105.2 Work exempt from permit.

(Ord. 5675 § 1 (part), 2025)

Section 510.7 of Chapter 5 of the California Mechanical Code is amended to read:

Section 510.7 Interior installations. In all buildings, the ducts shall be enclosed in a continuous enclosure extending from the lowest fire-rated ceiling or floor above the hood, through any concealed spaces, to or through the roof so as to maintain the integrity of the fire separations required

by the applicable building code provisions. The enclosure shall be sealed around the duct at the point of penetration of the lowest fire-rated ceiling or floor above the hood in order to maintain the fire resistance rating of the enclosure and shall be vented to the exterior of the building through weather-protected openings. [NFPA 96:7.7.1.2 – 7.7.1.4]

(Ord. 5675 § 1 (part), 2025)

Chapter 16.06

2025 CALIFORNIA RESIDENTIAL CODE,

CALIFORNIA CODE OF REGULATIONS, TITLE 24, PART 2.5*

Sections:

16.06.010 2025 California Residential Code adopted and amended.

Section R304.5 of the California Residential Code is added to read:

R304.5 Dwelling unit and congregate residence superficial floor area. Every dwelling unit and congregate residence shall have at least one room which shall have not less than 120 square feet of superficial floor area. Every room which is used for both cooking and living or both living and sleeping purposes shall have not less than 144 square feet of superficial floor area. Every room used for sleeping purposes shall have not less than 70 square feet of superficial floor area. When more than two persons occupy a room used for sleeping purposes the required superficial floor area shall be increased at the rate of 50 square feet for each occupant in excess of two. Guest rooms with cooking shall contain the combined required superficial areas of a sleeping and a kitchen, but not less than 144 square feet. Other habitable rooms shall be not less than 70 square feet.

Notwithstanding any provision of this section, children under the age of six shall not be counted for purposes of determining whether a family with minor children complies with the provisions of this Code.

For the purposes of this section, "superficial floor area" means the net floor area within the enclosing walls of the room in which the ceiling height is not less than seven feet six inches, excluding built-in equipment such as wardrobes, cabinets, kitchen units, or fixtures which are not readily removable.

(Ord. 5676 § 1 (part), 2025)

Section R319.1 of the California Residential Code is amended to read:

R319.1 Emergency escape and rescue opening required. Basements, habitable attics and every sleeping room shall have not less than one operable emergency escape and rescue opening. Where basements contain one or more sleeping rooms, an emergency escape and rescue opening shall be required in each sleeping room. Emergency escape and rescue openings shall open directly into a public way, or to a yard or court that opens to a public way.

Exceptions:

1. Storm shelters and basements used only to house mechanical equipment not exceeding a total floor area of 200 square feet (18.58 m2)

(Ord. 5676 § 1 (part), 2025)

Section R319.4.2.3 of the California Residential Code is added to read:

R319.4.2.3 Window well fall protection. Window wells with a vertical depth greater than 30 inches shall have guards on all sides. The guards shall be provided in accordance with Section R321.1. Openings shall comply with Section R321.1.3. Access ladder shall comply with Section R319.4.2.1 and shall extend from the bottom of the well to the top of the guard. Grates or similar barriers shall not be installed over the window well.

(Ord. 5676 § 1 (part), 2025)

Section R319.4.5 of the California Residential Code is added to read:

R319.4.5 Security bars. Fire Department plan check review and approval of all security bar submittals shall be required prior to the issuance of a building permit.

(Ord. 5676 § 1 (part), 2025)

Section 309.1.1 of the California Residential Code is amended to read:

R309.1.1 Design and installation. Where allowed, automatic sprinkler systems installed in townhouses shall be installed throughout in accordance with NFPA 13 and state and local standards.

(Ord. 5676 § 1 (part), 2025)

Section R309.2 of the California Residential Code is amended to read:

R309.2 One and two-family dwellings automatic fire sprinkler systems. Approved automatic sprinkler systems in new buildings and structures and in existing modified buildings and structures shall be provided in the locations described in this section. Automatic fire sprinklers shall be installed per the requirements set forth in Sections 903.2.1 through 903.2.18 of the California Building Code and as follows, whichever is the more restrictive:

1. An automatic sprinkler system shall be provided throughout all new buildings and structures.

Exception: New residential occupancies, buildings or structures that do not exceed 350 square feet of building area and contain no interior

plumbing fixtures.

2. An automatic sprinkler system shall be provided throughout all existing buildings when modifications are made that create an increase in fire

area to more than 3,600 square feet or when the addition is equal to or greater than 50% of the existing building square footage, whichever is more restrictive.

3 An automatic fire sprinkler system is required in basements when any of the following occurs:

a) New basements used for storage, utility, occupancy, or habitable space regardless of size.

b) Existing basements that are altered for the use of storage, utility, occupancy, or habitable space regardless of size.

c) Existing basements expanded by 50% or more.

If the addition or alteration is only the basement, then only the basement is required to be protected by fire sprinklers.

4. An automatic fire sprinkler system is required when either the roof structure, exterior walls, or combination of both has been removed,

altered and/or replaced in at least 50% of the existing structure.

5. An automatic sprinkler system shall be installed throughout when any change in use or occupancy creating a more hazardous fire/life safety

condition, as determined by the Fire Chief.

(Ord. 5676 § 1 (part), 2025)

Section R309.2.1 of the California Residential Code is amended to read as follows:

R309.2.1 Design and installation. Where allowed, automatic sprinkler systems installed in one- and two-family detached dwellings shall be installed throughout in accordance with NFPA 13D and state and local standards. Fire sprinkler protection is required under rear covered patios extending over four feet perpendicular from the exterior of the structure.

(Ord. 5676 § 1 (part), 2025)

Section R309.2.2 of the California Residential Code is added to read as follows:

Section R309.2.2 NFPA 13D sprinkler systems increase in design requirements. In a higher fire fighting hazardous conditions a four head fire sprinkler calculation and coverage in all closets, bathrooms and attics will be required in Residential and Group U Occupancies as determined by the Fire Code Official in the following conditions:

1. Structures located in the High Hazardous Fire Areas.

2. Structures where the combined fire area is 3,600 sq ft or larger.

3. Structures located 150 ft or greater from the Fire Department access roadways.

4. Basements and below grade structures.

(Ord. 5676 § 1 (part), 2025)

Section R309.3 of the California Residential Code is deleted in its entirety and amended as follows:

R309.3 Dwelling unit fire sprinkler systems. Fire sprinkler systems shall be designed and installed in accordance with NFPA 13D, State and local standards.

(Ord. 5676 § 1 (part), 2025)

Section R310.1 of the California Residential Code is amended to read:

R310.1 Smoke detection and notification. Listed single- and multiple-station smoke alarms complying with UL 217 shall be installed in accordance with the California Fire Code Sections 907.2.11.1 through 907.2.11.5 and manufacturer’s installation and use instructions.

Smoke alarms and smoke detectors shall be in compliance with this code or subject to the provisions of the Health and Safety Code, they shall also be listed and approved for rapid response to smoldering synthetic materials. All smoke alarms or detectors shall be of the photoelectric type or shall have equivalent detection capabilities in compliance with UL 217.

Exception: A photoelectric smoke alarm or detector shall be installed if located within 20 feet to a kitchen, fireplace or woodburning stove or

within five feet of a bathroom.

(Ord. 5676 § 1 (part), 2025)

Section R310.1.3 of the California Residential Code is added to read:

R310.1.3 Smoke alarms or detector end of life replacement. Smoke alarms or detectors shall be replaced every ten years or according to the manufacture guidelines, whichever is more restrictive.

(Ord. 5676 § 1 (part), 2025)

Section R311.7.5 of the California Residential Code is added to read:

R311.7.5 Carbon Monoxide alarms or detectors end of life replacement. Carbon monoxide alarms or detectors shall be replaced every ten years or according to the manufacture guidelines, whichever is more restrictive.

(Ord. 5676 § 1 (part), 2025)

Section R308 of the California Residential Code is amended to read:

R308.1 Address identification. Buildings shall be provided with approved address identification. The address identification shall be legible and placed in a position that is visible from the street or road fronting the property. Address identification characters shall contrast with their background. Address numbers shall be Arabic numbers or alphabetical letters. Numbers shall not be spelled out. Each character shall be not less than four inches (102 mm) in height with a stroke width of not less than 0.5 inch (12.7 mm). Where required by the fire code official, address identification shall be provided in additional approved locations to facilitate emergency response. Where access is by means of a private road and the building address cannot be viewed from the public way, a monument, pole or other sign or means shall be used to identify the structure. Address identification shall be maintained.

R308.1.1 Address illumination. Address identification required by Section R308.1 shall be illuminated.

R308.1.2 Address identification size. Address numbers and letters shall be sized as follows:

1. When the structure is between thirty-six (36) and fifty (50) feet from the road or other emergency means of access, a minimum of one-half

inch (0.5") stroke by six inches (6") high is required.

2. When the structure is fifty (50) or more feet from the road or other emergency means of access, a minimum of one inch (1") stroke by nine

inches (9") high is required.

(Ord. 5676 § 1 (part), 2025)

The following paragraph is added to Section R306.1 of the California Residential Code:

Palo Alto Flood Hazard Regulations. Notwithstanding the provisions of this Section R306, all construction or development within a flood hazard area (areas depicted as a Special Flood Hazard Area on Flood Insurance Rate Maps published by the Federal Emergency Management Agency) shall comply with the City of Palo Alto Flood Hazard Regulations (Palo Alto Municipal Code Chapter 16.52). Where discrepancies exist between the requirements of this code and said regulations, the more stringent requirements shall apply.

(Ord. 5676 § 1 (part), 2025)

Section 401 of the California Residential Code is amended to read:

R401.1 - R401.3 {'{'}CRC text not modified{'}'}

R401.4 Soils tests. Exception is added at end of the CRC text as follows:

Exception: Refer to PAMC 16.04.450

R401.4.1 Geotechnical evaluation. When permitted by the building official or designee, in lieu of a complete geotechnical evaluation, the load bearing values in T401.4.1(1) shall be assumed.

T401.4.1(2), R401.4.1.1 - R401.4.2 {'{'}CRC text not modified{'}'}

(Ord. 5676 § 1 (part), 2025)

Section 402.2.1 of the California Residential Code is amended to read:

R402.2.1 Materials for concrete. Materials for concrete shall comply with the requirements of Section R608.5.1, as amended by PAMC 16.14.240.

(Ord. 5676 § 1 (part), 2025)

Section R403 of the California Residential Code is amended as follows:

R403.1 - R403.1.1 {'{'}CRC text not modified{'}'}

R403.1.2 Continuous footing in Seismic Design Categories D0, D1, and D2.Exterior walls of buildings located in Seismic Design Categories D0, D1 and D2 shall be supported by continuous solid or fully grouted masonry or concrete footings. All required interior braced wall panels in buildings located in Seismic Design Categories D0, D1 and D2 shall be supported on continuous foundations.

R403.1.3 Footing and stem wall reinforcing in Seismic Design Categories D0, D1, and D2.Concrete footings located in Seismic Design Categories D0, D1 and D2, as established in Table R301.2(1), shall have not fewer than three No. 4 horizontal bars. One No. 4 horizontal bar shall be installed within 12 inches (305 mm) of the top of the stem wall and two No. 4 horizontal bars shall be located 3 to 4 inches (76 mm to 102 mm) from the bottom of the footing.

R403.1.3.1 Concrete stem walls with concrete footings. In Seismic Design Categories D0, D1 and D2 where a construction joint is created between a concrete footing and a stem wall, not fewer than one No. 4 vertical bar shall be installed at not more than four feet (1,219 mm) on center. The vertical bar shall have a standard hook and extend to the bottom of the footing and shall have support and cover as specified in Section R403.1.3.5.3 and extend not less than 14 inches (357 mm) into the stem wall. Standard hooks shall comply with Section R608.5.4.5. Not fewer than one No. 4 horizontal bar shall be installed within 12 inches (305 mm) of the top of the stem wall and two No. 4 horizontal bars shall be located three to four inches (76 mm to 102 mm) from the bottom of the footing.

R403.1.3.2 Masonry stem walls with concrete footings. In Seismic Design Categories D0, D1 and D2 where a grouted masonry stem wall is supported on a concrete footing, not fewer than one No. 4 vertical bar shall be installed at not more than four feet (1,219 mm) on center. The vertical bar shall have a standard hook and extend to the bottom of the footing and have support and cover as specified in Section R403.1.3.5.3 and extend not less than 14 inches (357 mm) into the stem wall. Standard hooks shall comply with Section R608.5.4.5. Not fewer than one No. 4 horizontal bar shall be installed within 12 inches (305 mm) of the top of the wall and two No. 4 horizontal bars shall be located three to four inches (76 mm to 102 mm) from the bottom of the footing. Masonry stem walls shall be solid grouted.

In Seismic Design Categories D0, D1 and D2 masonry stem walls without solid grout and vertical reinforcing are not permitted.

R403.1.3.3 - R403.1.7.4 {'{'}CRC text not modified{'}'}

R403.1.8 Foundations on expansive soils. Foundations and floor slabs for buildings located on expansive soils shall be designed in accordance with Section 1808.6 or Table 1809.7 of the California Building Code as amended in Municipal Code Section 16.04.470.

R403.1.8.1 {'{'}CRC text not modified{'}'}

(Ord. 5676 § 1 (part), 2025)

Section 404.1.3 of the California Residential Code is amended to read:

R404.1.3 Concrete Foundation Walls. Concrete foundation walls that support light-frame walls shall be designed and constructed in accordance with the provisions of this section, ACI 318, ACI 332, or PCA 100, as amended by PAMC Section 16.14.240. Concrete foundation walls that support above-grade concrete walls that are within the applicability limits of Section R608.2 shall be designed and constructed in accordance with the provisions of this section, ACI 318, ACI 332, or PCA 100, as amended by PAMC Section 16.14.240. Concrete foundation walls that support above-grade concrete walls that are not within the applicability limits of Section R608.2 shall be designed and constructed in accordance with the provisions of ACI 318, ACI 332, or PCA 100, as amended by PAMC Section 16.14.240. When ACI 318, ACI 332, PCA 100 or the provisions of this section, as amended by PAMC Section 16.14.240 are used to design concrete foundation walls, project drawings, typical details and specifications

are not required to bear the seal of the architect or engineer responsible for design, unless otherwise required by the state law of the jurisdiction having authority.

(Ord. 5676 § 1 (part), 2025)

Section R504.3.1 of the California Residential Code is added to read:

R504.3.1 Projections exposed to weather. Floor projections exposed to the weather and sealed underneath, including but not limited to balconies, landings, decks, and stairs shall be constructed of naturally durable wood, preservative-treated wood, corrosion-resistant (e.g. galvanized) steel, or similar approved materials.

(Ord. 5676 § 1 (part), 2025)

Section R506.1 of the California Residential Code is amended to read:

R506.1 General. Concrete slab-on-ground floors shall be designed and constructed in accordance with the provisions of this section of ACI 332, as amended by PAMC Section 16.14.240. Floors shall be a minimum 3 1/2 inches (89 mm) thick (for expansive soils, see Section R403.1.8). The specified compressive strength of concrete shall be as set forth in Section R402.2.

(Ord. 5676 § 1 (part), 2025)

Section R602.10.4.5 of the California Residential Code is added to read:

R602.10.4.5 Limits on methods GB and PCP. In Seismic Design Categories D0, D1, and D2, Method GB is not permitted for use as an intermittent braced wall panels, but gypsum board is permitted to be installed when required by this section to be placed on the opposite side of the studs form other types of braced wall panel sheathing. In Seismic Design Categories D0, D1, and D2, the use of Method PCP is limited to one-story single-family dwelling and accessory structures.

(Ord. 5676 § 1 (part), 2025)

Footnote e to Table R602.10.3(3) is amended to read as follows:

e. In Seismic Design Categories D0, D1 and D2, Method GB is not permitted and PCP is limited to one-story dwellings and accessory

structures.

(Ord. 5676 § 1 (part), 2025)

Section R608.5 of the California Residential Code is amended to read:

R608.5 Materials. Materials used in the construction of concrete walls shall comply with this section, as amended by PAMC Chapter 16.14.240.

(Ord. 5676 § 1 (part), 2025)

Section R703.8.5.1 of the California Residential Code is added to read:

R703.8.5.1 Locations. Flashing shall be installed at wall and roof intersections, gutters, wherever there is a change in roof slope or direction, and around roof openings. Where flashing is of metal, the metal shall be corrosion resistant with a thickness of not less than 0.019 inches (0.483 mm) (e.g. no. 26 galvanized sheet) and shall be primed and painted.

(Ord. 5676 § 1 (part), 2025)

Section R1003.9.2.1 is added to the California Residential Code to read:

R1003.9.2.1 Repairs, replacements and alterations. When any repair, replacement or alteration to the roof of an existing structure is performed, a spark arrester shall be installed on the existing chimney in accordance with Section R1003.9.2.

(Ord. 5676 § 1 (part), 2025)

Section BO109 of Appendix BO of the California Residential Code is added to read:

Section BO109.1 General. If a building permit is required at the request of the prospective permit applicant, the building official or his or her designee may meet with the prospective applicant to discuss plans for any proposed work under these provisions prior to the application for the permit. The purpose of this preliminary meeting is for the building official to gain an understanding of the prospective applicant’s intentions for the proposed work, and to determine, together with the prospective applicant, the specific applicability of these provisions.

(Ord. 5676 § 1 (part), 2025)