Hillsborough Municipal Code Ch. 15.03 Residential Code

Footnotes:

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Editor's note— Ord. No. 799, § 3(Exh. A), adopted December 9, 2025, in effect repealed Ch. 15.03 and enacted a new Ch. 15.03 as set out herein and as may later be amended. Former Ch. 15.03 pertained to similar subject matter and derived from Ord. No. 690, adopted December 13, 2010; Ord. No. 712, adopted November 12, 2013; Ord. No. 742, adopted November 14, 2016; Ord. No. 745, June 10, 2017; Ord. No. 757, October 14, 2019; Ord. No. 758, November 12, 2019; Ord. No. 786, adopted November 28, 2022; and Ord. No. 788, adopted January 9, 2023.

The purpose of this code is to establish the minimum requirements to safeguard the public health, safety and general welfare through structural strength, means of egress facilities, stability, access to persons with the disabilities, sanitation, adequate lighting and ventilation, and energy conservation; safety to life and property from fire and other hazards attributed to the built environment; and to provide safety to fire fighters and emergency responders during emergency operations.

Sections within this chapter may include both local amendments to Title 24 as adopted therein and local development standards related to construction in the town that are not part of Title 24.

(Ord. No. 799, § 3(Exh. A), 12-9-2025)

The rules, regulations and requirements published in the 2025 California Residential Code, including Appendix Chapters BF, BO, CJ, as contained in the California Building Standards Code, are hereby adopted as and for the rules, regulations, and standards for the town as to all matters contained therein except as herein otherwise provided.

A. One copy of the 2025 California Residential Code shall at all times be kept on file at the town building department. It shall be accompanied by one copy of this chapter (as well as any additional subsequent amendments) to show the amendments to the 2025 California Residential Code.

B. In the event of any conflict or inconsistency between the provisions of this code and the 2025 California Residential Code, when applied to any particular case, that requirement which establishes the higher degree of safety shall be complied with unless otherwise stated in this code.

C. No provision of the 2025 California Residential Code, or as amended hereby, shall be deemed to supersede any other provision of this code.

(Ord. No. 799, § 3(Exh. A), 12-9-2025)

The 2025 California Residential Code as adopted by this chapter is hereby amended in its application to the town as set forth within Sections 15.03.040 through 15.03.220.

Any section within this chapter that modifies the 2025 California Residential Code shall include the code section being changed or modified and language which describes the nature of the change or modification. Sections that do not include such reference or language are local development standards and are not amendments to Title 24.

(Ord. No. 799, § 3(Exh. A), 12-9-2025)

Section R108.2 is replaced in its entirety to read as follows:

R108.2 Schedule of permit and penalty fees.

A. A fee shall be set forth in the town's master fee schedule, plus any additional fees which may be established or mandated by state or federal law or city ordinance.

B. The value to be used in computing the building permit fee, the plan review fee and other fees shall be the total value of all construction work for which the permit is issued as well as all finish work, painting, roofing, electrical, plumbing, heating, air conditioning, elevators, fire extinguishing systems, etc., and any other permanent construction or equipment.

C. A fee for each permit shall be paid as required, in accordance with the master fee schedule, including subsection (C)(1) and (C)(2) of this section.

1. Whenever a permit fee is required by this chapter to be paid prior to starting work and such work is started prior to obtaining a permit, the scheduled fee shall be the applicable permit fee as set forth in Table No. 1-A found in the master fee schedule, plus an additional amount of up to ten times the applicable permit fee. The exact amount shall be set by the building official in the amount that will, in his or her good faith estimate, recover the cost of town staff time expended to deal with the problems caused by the unpermitted work.

2. If a stop work order is issued, it may not be lifted until a permit reactivation fee has been paid in the amount of not less than two hundred fifty dollars up to one thousand dollars, the exact amount to be set by the building official in the amount that will, in his or her good faith estimate, recover the cost of town staff time expended to deal with the problems involved in the issuance of the stop work order.

3. A document imaging charge shall be charged upon submission of every application for a combination, building, electrical, plumbing, mechanical, grading and or encroachment permit.

(Ord. No. 799, § 3(Exh. A), 12-9-2025)

If a contractor's bond prior to the issuance of any permit for a new residence or other work to which this section is applicable in the opinion of the building official, the applicant shall file with the building official a performance, maintenance or completion bond in the amount of the estimated cost of the work allowed or required under the provisions of the permit. The purpose and intent of the bond is to insure the completion of all work including the installation of any required curbs, gutter, street, sewer, sewer laterals, storm sewers and water mains; the repair of any damage to any of the above; and the removal of all debris from streets, gutters, parking strips areas, and the job site. Upon completion of the permitted work, such bond shall be exonerated, less any charges against the applicant for any work required to be done or contracted to be done by the town to complete the work.

(Ord. No. 799, § 3(Exh. A), 12-9-2025)

Section R110.2 is amended to read as follows:

R110.2 Certificate of occupancy issued. No final inspection by the building official as to all or any portion of a development shall be deemed complete, and no certificate of occupancy or temporary certificate of occupancy shall be issued, nor shall any occupancy occur in accordance with CBC 3312.1, unless and until the installation of the prescribed fire protection facilities and access ways have been completed and approved by the fire chief or designee. Once the prescribed fire protection facilities and access way have been completed and approved as required, and once final inspection by the building official is deemed complete, the building official shall issue a certificate of occupancy containing the address or APN of the property and the name and address of the owner or the owner's agent. The certificate shall also include a description of the portion of the work for which the certificate is being issued and a statement that such work has been inspected for compliance. The Building Official will indicate his/her name and sign the certificate, the code edition under which the work was permitted, whether the structure was required and thus contains an automatic fire sprinkler system, and any further stipulations or conditions that the permit was issued.

(Ord. No. 799, § 3(Exh. A), 12-9-2025)

When required by the fire code official, plans submitted to the building official for a permit shall be reviewed by the fire code official to determine compliance with all applicable standards including the California Fire Code and California Wildland-Urban Interface Code. Upon review a written report shall be returned to the building official listing deficiencies or compliance with the code.

(Ord. No. 799, § 3(Exh. A), 12-9-2025)

Section R309.2 is replaced in its entirety to read as follows:

R309.2 One- and two-family dwellings automatic fire sprinkler systems. An automatic fire sprinkler system shall be installed in:

1. New one- and two-family dwellings.

2. Existing one- and two-family dwellings that have either a total building floor area of more than 2,000 square feet or more than two stories in height, and when permit requiring additions and/or alterations to the dwelling exceed either 1,500 square feet in area or 20% of the total square footage for a building over 7,500 square feet.

3. Accessory dwelling units (ADU) when:

3.1.

The ADU will be in accessory to an existing primary dwelling that has an existing automatic fire sprinkler system; or

3.2.

The ADU will be in accessory to a proposed new primary dwelling which requires installation of an automatic fire sprinkler system under 309.2(1) above; or

3.3.

The ADU will be in accessory to an existing primary dwelling undergoing additions or alterations that is required to have an automatic residential fire sprinkler system installed under R309.2(2) above.

Exceptions:

1. Detached carports or garages less than 2,000 square feet in area and separated from residential buildings complying with R302.1.

2. Detached structure, other than an ADU, whose closest exterior wall is located in excess of 10 feet from the closest exterior wall of the automatic fire sprinkler system requiring primary dwelling on the same lot.

3. Additions and/or alterations necessitated for:

a. Building roof repair/replacement;

b. Fire damage repair;

c. Building heating and/or cooling unit repair/replacement; and/or

d. Any other federal, state and local construction code upgrade requirements including but not limited to the seismic retrofit requirements, asbestos, and other hazardous material abatement.

Section 15.03.112 outlines the standard used to calculate additions and/or alterations for purposes of determining applicability of this section.

(Ord. No. 799, § 3(Exh. A), 12-9-2025)

Section R309.3.1.2 is replaced in its entirety to read as follows:

R309.3.1.2 Required sprinkler locations.

1. Sprinklers shall be installed to protect all areas of a dwelling unit, including coverage of:

a. Attic access openings

b. Areas of attics and crawl spaces containing storage, mechanical and/or electrical equipment.

2. Inspector Test Valves shall be provided for each system and located the furthest point away from the sprinkler riser for buildings greater than 3,600 square feet.

(Ord. No. 799, § 3(Exh. A), 12-9-2025)

A. The standard for calculating whether additions and/or alterations of an existing building triggers automatic fire sprinkler system installation as described in Section 15.03.110 shall be based on the following criteria:

1. Cumulative Square Footage of Each Room Being Added or Altered.

a. A room is considered added and/or altered when fifty percent or more of interior wall or ceiling sheeting covering the wall planes of the room is removed, replaced, or new.

b. Wall plane area of a room does not include the area of windows, doors, and openings.

2. Aggregated Additions and Alterations. Cumulative added and/or altered square footage or replacement costs of additions and/or alterations will be aggregated to include any room square footage added and/or altered within a two-year period from the closure date of any previous additions and/or alterations.

B. Exceptions. Wall or ceiling sheeting removal, replacement, or new installment shall not be calculated when necessitated for:

1. Building roof repair/replacement;

2. Fire damage repair;

3. Building heating and/or cooling unit repair/replacement; and

4. Any other federal, state and local construction code upgrade requirements including but not limited to the seismic retrofit requirements, asbestos, and other hazardous material abatement.

(Ord. No. 799, § 3(Exh. A), 12-9-2025)

When a building is partially retrofitted with an approved automatic sprinkler fire extinguishing system pursuant to this section, the building fire extinguishing system retrofit shall be completed throughout the unprotected building interior areas within two years from completing the initial partial retrofit. When a property owner or responsible party of a commercial or residential building chooses this option, the property owner shall file a deed restriction with San Mateo County Assessor's Office and obtain a performance bond to ensure compliance. The bond shall be in an amount equal to or greater than the estimated cost of completion, as determined by Central County Fire Department.

(Ord. No. 799, § 3(Exh. A), 12-9-2025)

Section R308.1 is replaced in its entirety to read as follows:

308.1 Address identification. All buildings and dwellings, including accessory dwelling units, shall be provided with approved address identification and address identification shall be maintained. 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, be Arabic numbers or alphabetical letters, and numbers shall not be spelled out. Address identification shall be in a size of numbers and manner as follows:

1. When the structure is thirty-six (36) to fifty (50) feet from the street or fire apparatus access, a minimum of one-half inch (½") stroke by six inches (6") high is required.

2. When the structure is more than fifty (50) feet from the street or fire apparatus access, a minimum of one inch (1") stroke by nine inches (9") high is required.

3. Multi-tenant building numbers or letters shall be designated on all occupancies within a building. Size shall be a minimum of one-half inch (1/2") stroke by four inches (4") high and on a contrasting background. Directional address numbers or letters shall be provided. Said addresses or numbers shall be posted at a height no greater than 5 feet, 6 inches (5' 6") above the finished floor and shall be either internally or externally illuminated in all new construction.

Rear addressing. When required by the chief, approved numbers or addresses shall be placed on all new and existing buildings in such a position as to be plainly visible and legible from the fire apparatus road at the back of a property or where rear parking lots or alleys provide and acceptable vehicular access. Number stroke and size shall comply with the above requirements as applicable.

(Ord. No. 799, § 3(Exh. A), 12-9-2025)

Section R902.1 is replaced in its entirety to read as follows:

R902.1 Roof assemblies. All roof and roof deck assemblies shall be Class A. All roof assemblies, coverings, and materials shall be tested in accordance with ASTM E 108 or UL 790, shall be listed and identified as to class by an approved testing agency, and comply with R904 and R905 where applicable. In addition, fire-retardant-treated wood roof coverings shall be tested in accordance with ASTM D 2898. The minimum roof coverings installed on buildings shall comply with the CBC Table 1505.1 as amended in 15.04.131.

(Ord. No. 799, § 3(Exh. A), 12-9-2025)

Section R902.1.2 is replaced in its entirety to read as follows:

R902.1.2 Roof covering replacements in all zones. Roof covering within all other areas shall be Class A. The entire roof covering of every existing structure where more than 50 percent of the total roof area is replaced within any one-year period, the entire roof covering of every new structure, and any roof covering applied in the alteration, repair or replacement of the roof of every existing structure, shall be a fire-retardant roof covering that is at least Class A.

(Ord. No. 799, § 3(Exh. A), 12-9-2025)

Except as otherwise provided in this code or as indicated in the town's green infrastructure plan approved by resolution of the city council, in all zones, water from the roof of any building and from any paved area which would flow by gravity over a public right-of-way shall be carried by means of conductors under the parking strip area and through the curb to the gutter, or other approved location.

(Ord. No. 799, § 3(Exh. A), 12-9-2025)

No storm water from any roof, impervious surfaces, point discharge or any paved or developed area shall be allowed to drain to adjacent properties nor shall this water be connected to the city's sanitary sewer system. Regardless of the slope of the source property, such water shall drain to either artificial or natural storm drainage facilities by gravity or pumping.

(Ord. No. 799, § 3(Exh. A), 12-9-2025)

Section R1003.9.2 is amended to read as follows:

R1003.9.2 Spark arrestors. All chimneys, regardless of material, which are attached to any appliance or fireplace that burns solid fuel, shall be equipped with an approved spark arrestor, either internally or externally mounted. Any spark arrestor to be mounted internally shall not be installed until installation plans for such arrestor have been submitted to and approved by the building division. Where a spark arrestor is installed on a masonry chimney, the spark arrestor shall meet all of the following:

1. The net free area of the arrestor shall be not less than four times the net free area of the outlet of the chimney flue it serves.

2. The arrestor screen shall have heat and corrosion resistance equivalent to 12 gage wire, 19-gage galvanized steel or 24-gage stainless steel.

3. Openings shall not permit the passage of spheres having a diameter greater than ½ inch (12.7 mm) nor block the passage of spheres having a diameter less than 3/8 inch (9.5 mm).

4. The spark arrestor shall be located with access for cleaning and the screen or chimney cap shall be removable to allow for cleaning of the chimney flue.

(Ord. No. 799, § 3(Exh. A), 12-9-2025)

All chimneys as described in 2025 605.2.1 of the 2025 California Fire Code shall be retroactively protected with a spark arrestor when one or more of the following conditions exist:

1. Upon the sale or transfer of the real property on which any chimney is located the transfer of title shall not be made until each such chimney contains the required spark arrestor, properly installed and in proper working order.

2. In the event of any construction on such property for which a building permit is required, the final building permit signoff shall not be made until each such chimney has a spark arrestor installed and is in proper working order.

(Ord. No. 799, § 3(Exh. A), 12-9-2025)

All persons to whom permits are issued pursuant to any provision of this code shall, as a condition to the continuing validity of the permit, maintain the subject building site with proper parking, sanitary facilities, material storage, dust and erosion controls on the property site, including, without limitation, all structures thereon, free of all open trenches, tripping hazards, broken ware, empty cans, rubbish, garbage, metal pieces or parts, and all other refuse (collectively "debris"). The presence of debris is contrary to the purposes and intent of this code and is hereby deemed to pose a threat to the health, property, and public welfare of the inhabitants of the town. Violations of the duty to maintain building sites as described herein shall be punishable in the same manner as any other violation of this code.

(Ord. No. 799, § 3(Exh. A), 12-9-2025)

The placards provided by the California Office of Emergency Services (OES) are to be used during a "Post Disaster Safety Assessment" performed by the city building staff in the aftermath of any disaster. The post disaster assessment placards carry the weight of law per the direction of the California Office of Emergency Services.

(Ord. No. 799, § 3(Exh. A), 12-9-2025)

When, in the judgment of the building department, it is reasonably necessary to amend the provisions of the California Residential Code due to local climatic, geological, topographical or other statutorily permissible conditions, the building official shall prepare and submit the proposed amendments to the city council for consideration at the next regularly scheduled city council meeting. Before adopting any changes or modifications in the requirements contained in the provisions published in the California Residential Code, or in any other regulations adopted hereunder, the city council shall make an express finding that such modifications or changes are reasonably necessary because of local climatic, geological, topographical or other statutorily permissible conditions. Such finding shall be made available as a public record. Upon approval by the city council and filing of the city council's findings with the California Building Standards Commission (CBSC) or other governing body, such amendments shall be added to and become a part of the provisions of this chapter.

From October 1, 2025, through June 1, 2031, the town is limited in its ability to modify provisions related to residential units. Allowable findings for modifications during this time are limited to:

1. Modifications previously adopted and filed with the CBSC before September 30, 2025;

2. Administrative changes related to administration of the code;

3. Emergency health and safety measures as deemed by the CBSC;

4. Needed to implement a greenhouse gas emissions reduction strategy as outlined in a general plan adopted before June 10, 2025; or

5. Related to fire home hardening.

(Ord. No. 799, § 3(Exh. A), 12-9-2025)

As successive editions of the California Residential Code are promulgated and incorporated by reference in the California Building Standards Code, the building department, under the guidance and direction of the building official, shall review the provisions of the new code in order to determine whether they are consistent with the provisions of the California Residential Code then enforce as modified by the provisions of this chapter. The building official shall submit a list of recommendations with respect to such changes (if any) to the city council. Upon review and adoption by the city council, according to the procedure set out in Section 15.03.240, such revised version of the California Residential Code, together with all amendments thereto which are recommended by the building official and/or required by the provisions of this chapter, shall govern all buildings and construction within town limits.

(Ord. No. 799, § 3(Exh. A), 12-9-2025)