Millbrae Municipal Code Art. II Residential Code

The Residential Code as published by the International Code Council and as amended by the California Building Standards Commission known as the "California Residential Building Code, 2025 Edition," including Appendix BF Patio Covers; Appendix BG Sound Transmission; Appendix BO Existing Buildings; and Appendix CI Swimming Pool Safety Act hereinafter collectively called the "Residential Code," is adopted and by reference incorporated in this chapter as if fully set forth as the building code of the city establishing the rules, regulations and standards within this city as to all matters therein contained; subject, however, to the amendments, additions and deletions set forth in this chapter. The mandatory requirements of the adopted appendices to the Residential Code shall be enforceable to the same extent as if contained in the body of the Residential Code.

Whenever reference is made within the Millbrae Municipal Code to the Uniform Codes, National Codes or any codes regulating the construction or maintenance of any building, structure or appurtenance thereto, such codes shall commonly mean the currently adopted building code set forth in this chapter.

The Residential Code regulates the erection, construction, enlargement, alteration, repair, moving, removal, demolition, conversion, occupancy, equipment, use, height, area and maintenance of all One and Two Family Dwellings and townhouses not more than three stories above grade plane in height in the City, and is adopted and by reference incorporated in this chapter as if fully set forth, subject to the amendments set forth in this chapter. The requirements of Residential Code Appendix Chapters BF Patio Covers; BG Sound Transmission; BO Existing Buildings; and Appendix CI Swimming Pool Safety Act are enforceable to the same extent as if contained in the body of the Residential Code and as amended herein.

Residential Code Section 1.11.2.1.1 is amended to read as follows:

Section 1.11.2.1.1 Enforcement.

The responsibility for enforcement of building standards adopted by the State Fire Marshal and published in the California Building Standards Code relating to fire and panic safety and other regulations of the State Fire Marshal shall, except as provided in Section 1.11.2.1.2, be delegated to the City Building Official for the enforcement of the building standards as they relate to One- and Two-Family Dwellings, as described in Section R310.1 of Part 2 of the California Building Code.

Exception: Automatic Fire Extinguishing Systems designed and installed in accordance with California Residential Code Section R313.

Residential Code Section R105.2, "Building: 2. Fences not over 7 feet (2134 mm) high," is amended to read as follows:

2. Fences that are any manmade barrier forming a physical boundary constructed of wood, concrete, stone, brick, lattice, metal, chain, cable, plastic, or dense planting materials.

Residential Code Section R106 is amended to add Section 106.6 to read as follows:

106.6 SUBSTANTIAL IMPROVEMENTS. Permit applications that are determined to meet the definition of a Substantial Improvement, are considered as new construction and shall comply with the new construction requirements under the Millbrae Municipal Code. These requirements may include, but are not limited to the following:

1. Planning Requirements — including Planning Commission Review.

2. California Energy Code Requirements, as amended by the City of Millbrae.

3. Seismic Retrofit of the foundation and framing system.

4. An Automatic Fire Extinguishing System.

5. A Fire Alarm System.

6. Building Addressing.

Residential Code Section R105.3.2 is amended to read as set forth in MMC § 9.05.030.

Residential Code Section R105.5 and R105.5.1 are amended to read as set forth in MMC § 9.05.040.

Residential Code Section R108.3 is amended to read as set forth in MMC § 9.05.050.

Residential Code Section R111.3 is amended to read as set forth in MMC § 9.05.070.

Section R111 of the California Residential Code is amended by adding Section R111.4 to read as set forth in MMC § 9.05.080.

Residential Code Section R112.1 of the California Residential Code is amended by adding Section R112.1.1 to read as set forth in MMC § 9.05.090.

Residential Code Section R302.1 is amended by adding Section R302.1.1 to read as follows:

Section R302.1.1. Separation Distance Measurement.

Walls, projections, openings and penetrations in walls perpendicular to the line used to determine separation distances shall be measured from the finished face of the building.

Residential Code Section R317.5.1 is amended to delete the "Exception" from the Section.

Residential Code Section R309.1 "Exception" is amended to read as follows:

R309.1 TOWNHOUSE AUTOMATIC FIRE SPRINKLER SYSTEMS. An automatic residential fire sprinkler system shall be installed in new Townhouses. An automatic residential fire sprinkler system is required when additions and/or alterations to existing townhouse buildings with a total building floor area of more than 2,000 square feet or more than two stories in height, and when additions or alterations for which a building permit is required exceeds 900 square feet in area or 20% of the total square footage of the entire completed building.

Residential Code Section R309.2 is amended to read as follows:

R309.2 ONE- AND TWO-FAMILY DWELLINGS AUTOMATIC FIRE SPRINKLER SYSTEMS.

An automatic residential fire sprinkler system shall be installed in new one- and two-family dwellings.

1. An automatic residential fire sprinkler system is required when additions and/or alterations to existing one- and two-family dwellings, with a total building floor area more than 2,000 square feet or more than two stories in height, and when additions or alterations for which a building permit is required exceeds 900 square feet in area.

The entire square footage shall be considered added or altered when at least fifty percent (50%) or greater of the interior wall sheeting or ceiling of any one wall within a room or area is new, removed, or replaced.

2. Detached structures classified as an Accessory Dwelling Unit (ADU), shall be protected with an automatic fire sprinkler system throughout where the primary dwelling is provided with an automatic fire sprinkler system. If work occurs within either building within a two-year period, of completion of the ADU, and in excess of 900 square feet in area fire sprinklers shall be provided throughout both buildings.

Exceptions:

1. Detached Group U Occupancies, of less than 1,200 square feet and located in excess of 10 feet from other buildings or structures on the property.

2. Additions or alterations of residential building that do not exceed 20% of the total square footage of the entire completed building.

3. Building roof repair/replacement; fire damage repair; building heating and/or cooling unit repair/replacement; and 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.

Residential Code Section R309.3.1.2 is amended to read as follows:

Section R309.3.1.2 Required Sprinkler Locations.

Sprinklers shall be installed to protect all areas of a dwelling unit and any attached Group U Occupancies.

Exception:

1. Detached Group U Occupancies less than 1,200 square feet and separated from other buildings and structures on the property by at least ten (10) feet.

2. Sprinkler coverage shall be provided in the following locations:

a. Attic access openings.

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

Residential Code Section R309.3.2 is amended to add Section R309.3.2.7 to read as follows:

Section R309.3.2.7 Additions and Alterations.

The standard for determining the size of addition and/or alteration for determining the threshold for fire sprinkler systems shall be determined by the following:

1. The square footage of every room being added and/or altered shall be included in the calculation of total square footage of addition and/or alteration.

2. The entire square footage shall be considered added or altered when at least fifty percent (50%) or greater interior wall sheeting or ceiling of any one wall within a room or area is new, removed, or replaced.

The size of additions and alterations used in calculating shall not be cumulative with regard to individual additions or alterations in a building unless the following circumstance applies:

When more than one (1) addition and/or alteration for which building permits are required are submitted within a two (2) year period from the final closure of the initial permit, the sum of the size of these additions or alterations during this two (2) year period shall be aggregated for the purpose of determining calculations in Section R309.3.1.

Exception:

Building roof repair/replacement; fire damage repair; building heating and/or cooling unit repair/replacement; and 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 R309.3.2 of the California Residential Code is amended by adding Section R309.3.2.8 to read as follows:

Section R309.3.2.8 Partial Installations.

When a One- and Two-Family dwelling is partially retrofitted with an approved automatic sprinkler fire system pursuant to this section, the building's fire extinguishing system shall be completed throughout the remainder of the building's interior areas within two (2) years from completing the initial partial retrofit. The property owner shall file a deed restriction with San Mateo County Assessor's Office and obtain a performance bond with Central County Fire Department to ensure completion of the fire sprinkler installation.

Residential Code Section R308.1 is amended to read as set forth in MMC § 9.05.130.

Residential Code Section R309 is amended by adding Section R309.3.3.5 to read as follows:

Section R309.3.3.5 Inspector Test Valves.

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.

Residential Code Section R902.1.2 is amended to read as follows:

Section R902.1.2 Roof covering in all other areas.

The entire roof covering of every existing structure where more than 300 square feet 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 a roof of every existing structure, shall be a fire-retardant roof covering that is a least Class B.