Updated : 04/22/2024

Overview

San Mateo County adopted parts of the 2013 California Building Standards Code: the California Building Code, California Residential Code, California Electrical Code, California Plumbing Code, California Mechanical Code, California Historical Building Code; also, the California Energy Code, California Fire Code, California Existing Building Code and California Green Building Standards Code. San Mateo County, Cal., Building Regulations [2014] ch. 3, arts. 1, 5, 2, 3, 4, 11; San Mateo County, Cal., Building Regulations [2014] ch. 3, art.1 §§ 9100 and 9119.

Helpful resources for San Mateo County, California include the following.

• PLRB, Ordinance and Law Coverage Discussion for California

Residential Building Code

California adopted a statewide mandatory residential code that will control; however, local governments are free to make laws more strict (with some limitations).See PLRB, California Building Codes for more information on state level codes.

San Mateo County adopted the 2012 IRC, locally. Note that adoptions usually come with amendments. So, it is important to review those amendments in addition to the unamended model code.

You can find a copy of the model code here.

You can find information about amendments to the model code here.

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2022 California Residential Code (2021 IRC)(San Mateo County, CA APPENDIX ONE - TABLE SHOWING DISPOSITION OF FORMER ORDINANCES IN THE SAN MATEO COUNTY ORDINANCE CODE AND ORDINANCES WHICH HAVE BEEN REPEALED OR NOT CODIFIED)

...8486 One and Two Family Dwelling Code...

Drip Edge

Drip Edge: Yes

Ice Barrier

Comments

The County amended the State code for roofing provisions as follows:

1. The following requirements shall apply to all new buildings or structures and existing structures that require a building permit issued by San Mateo County.

a. The roof covering for every new building or structure, or any existing building or structure which is undergoing a re-roof and all materials applied as part of a roof covering assembly, shall have a minimum fire rating of Class B or higher, treated in accordance with California Building Standards Code, Section(s) 1505, Table 1505.1, and Section 1505.1.3. Where required by the California Building Standards Code or other provision(s) of law, roof coverings must meet a higher fire rating.

b. Subsection 1.a of this section shall not apply to buildings or structures that are less than 120 square feet in floor area.

c. Any person installing or constructing a roof covering shall, immediately upon completion of the roof covering, provide certification of the roof covering classification to the building owner and to the inspection authority having jurisdiction.

2. The requirements of this section are minimum standards for new construction and re-roofing of existing structures. Where the International Building Code, International Residential Code, International Fire Code, or the California Building Standards Code(s) contains higher standards or additional or more stringent requirements than required by this section, those additional or more stringent requirements shall apply. Further, nothing in this section shall prevent any fire authority having jurisdiction from adopting and enforcing regulations imposing more stringent requirements than those provided by this section.

San Mateo County, Cal., Building Regulations [2014] ch.3, art.1 § 9113. Minimum Roofing Standard for Fire Resistance.

The County's amendments did not reference Table R301.2(1) Cimatic and Geographic Design Criteria.

Existing Buildings

Existing buildings, meaning buildings that were built in accordance to code at the time of construction, typically merit extra consideration in a current updated code.

Existing Buildings: San Mateo County amended the 2013 California Residential Code with administrative provisions for existing buildings as follows:

The following provisions shall govern additions, alterations, repairs, and changes of use or occupancy in existing buildings:

1. For the purpose of this section, the term “building or structure” shall include any heating, cooling, ventilating, or similar mechanical equipment or system, any electrical equipment or system, plumbing equipment or system, swimming pools, spas, decks, mobile homes, recreational vehicles, trailers, agricultural buildings, or accessory structures governed by this code.
2. Any addition, alteration, or repair to, of change of use of, or change of occupancy in a building or structure shall comply with the provisions for new buildings and structures set out in the code, except as may otherwise be provided in this section and in the California Building Standards Code, latest adopted edition …
3. When additions, alterations, or repairs within any 12-month period from the date of completion of any permit exceed fifty percent (50%) of the value of an existing building or structure, as determined by the Building Official, such building or structure shall be made in its entirety to conform with the requirements for new buildings or structures, including any requirements of the fire department or district (see also Section 9114).
4. Additions, alterations and repairs exceeding 25 percent (25%) but not exceeding 50 percent of the value of the existing building or structure and complying with the requirements for new buildings or structures may be made to such building or structure within a 12-month period without making the entire building or structure comply. The new construction shall conform with the requirements of the construction codes for a new building of like area, height, use and occupancy.
5. Structural additions, alterations, and repairs to any portion of an existing building or structure shall comply with all requirements for new buildings or structures; except that such structural additions, alterations, or repairs, when determined by the Building Official to be minor, may be made with the same material of which the building or structure is constructed. This section shall not apply to the installation or replacement of glass in hazardous locations.
6. Alterations or repairs, not exceeding 25 percent (25%) of the value of an existing building or structure, which are non-structural and do not affect any member or part of the building or structure and which meet fire resistance standards, may be made with the same materials of which the building or structure is constructed. This section shall not apply to the installation or replacement of glass in hazardous locations.
7. Not more than 25 percent (25%) of the roof covering of any building or structure shall be replaced in any 12-month period unless the new roof covering is made to conform with the requirements for new buildings. EXCEPTION 1: Roof covering on existing buildings or structures shall not be required to comply with Section 9113 when determined by the Building Official to create a hardship due to structural restraints.
8. Buildings or structures in existence at the time of the passage of this code may continue in their existing occupancy, if such use or occupancy was legal at the time of passage, provided such continued use is not dangerous to life or property.
9. No change in the character of occupancy or use of a building or structure shall be made without a Certificate of Occupancy. The Building Official may issue a Certificate of Occupancy without certifying that the building complies with all the provisions of these codes so long as he or she finds to do so will not endanger life.
10. All buildings or structures, both existing and new, and all parts thereof shall be maintained in a safe and sanitary condition. All devices or safeguards, which are required by the construction codes in a building or structure when erected, altered, or repaired, shall be maintained in a good working order. The owner or the owner’s designated agent shall be responsible for the maintenance of buildings and structures.
11. Any building or structure, including mobile homes, and factory built homes moved into or relocated on existing parcels or to a new parcel within those areas of San Mateo County within the jurisdiction of the Building Official shall meet standards required by this code for new buildings or structures. Permits for manufactured homes may be denied if more than ten (10) years has elapsed between the date of manufacture and the date of application for a permit to install the manufactured home.

San Mateo County, Cal., Building Regulations [2014] ch.2, art.2 § 9022. Existing Buildings.

Commercial Building Code

San Mateo County adopted the 2012 IBC, statewide with limitations. Note that adoptions usually come with amendments. So, it is important to review those amendments in addition to the unamended model code.

You can find a copy of the code here.You can find information about amendments to the model code here.

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2022 California Bldg. Code, Part 2 (2021 IBC)(San Mateo County, CA Municipal Code)

...Adoption not found...

Comments

The County amended the State code for roofing provisions as follows:

1. The following requirements shall apply to all new buildings or structures and existing structures that require a building permit issued by San Mateo County.

a. The roof covering for every new building or structure, or any existing building or structure which is undergoing a re-roof and all materials applied as part of a roof covering assembly, shall have a minimum fire rating of Class B or higher, treated in accordance with California Building Standards Code, Section(s) 1505, Table 1505.1, and Section 1505.1.3. Where required by the California Building Standards Code or other provision(s) of law, roof coverings must meet a higher fire rating.

b. Subsection 1.a of this section shall not apply to buildings or structures that are less than 120 square feet in floor area.

c. Any person installing or constructing a roof covering shall, immediately upon completion of the roof covering, provide certification of the roof covering classification to the building owner and to the inspection authority having jurisdiction.

2. The requirements of this section are minimum standards for new construction and re-roofing of existing structures. Where the International Building Code, International Residential Code, International Fire Code, or the California Building Standards Code(s) contains higher standards or additional or more stringent requirements than required by this section, those additional or more stringent requirements shall apply. Further, nothing in this section shall prevent any fire authority having jurisdiction from adopting and enforcing regulations imposing more stringent requirements than those provided by this section.

San Mateo County, Cal., Building Regulations [2014] ch.3 art. 1 § 9100. Minimum Roofing Standard for Fire Resistance.

Existing Buildings

Existing Buildings: San Mateo County amended the 2013 California Building Code with administrative provisions for existing buildings as follows:

The following provisions shall govern additions, alterations, repairs, and changes of use or occupancy in existing buildings:

1. For the purpose of this section, the term “building or structure” shall include any heating, cooling, ventilating, or similar mechanical equipment or system, any electrical equipment or system, plumbing equipment or system, swimming pools, spas, decks, mobile homes, recreational vehicles, trailers, agricultural buildings, or accessory structures governed by this code.
2. Any addition, alteration, or repair to, of change of use of, or change of occupancy in a building or structure shall comply with the provisions for new buildings and structures set out in the code, except as may otherwise be provided in this section and in the California Building Standards Code, latest adopted edition …
3. When additions, alterations, or repairs within any 12-month period from the date of completion of any permit exceed fifty percent (50%) of the value of an existing building or structure, as determined by the Building Official, such building or structure shall be made in its entirety to conform with the requirements for new buildings or structures, including any requirements of the fire department or district (see also Section 9114).
4. Additions, alterations and repairs exceeding 25 percent (25%) but not exceeding 50 percent of the value of the existing building or structure and complying with the requirements for new buildings or structures may be made to such building or structure within a 12-month period without making the entire building or structure comply. The new construction shall conform with the requirements of the construction codes for a new building of like area, height, use and occupancy.
5. Structural additions, alterations, and repairs to any portion of an existing building or structure shall comply with all requirements for new buildings or structures; except that such structural additions, alterations, or repairs, when determined by the Building Official to be minor, may be made with the same material of which the building or structure is constructed. This section shall not apply to the installation or replacement of glass in hazardous locations.
6. Alterations or repairs, not exceeding 25 percent (25%) of the value of an existing building or structure, which are non-structural and do not affect any member or part of the building or structure and which meet fire resistance standards, may be made with the same materials of which the building or structure is constructed. This section shall not apply to the installation or replacement of glass in hazardous locations.
7. Not more than 25 percent (25%) of the roof covering of any building or structure shall be replaced in any 12-month period unless the new roof covering is made to conform with the requirements for new buildings. EXCEPTION 1: Roof covering on existing buildings or structures shall not be required to comply with Section 9113 when determined by the Building Official to create a hardship due to structural restraints.
8. Buildings or structures in existence at the time of the passage of this code may continue in their existing occupancy, if such use or occupancy was legal at the time of passage, provided such continued use is not dangerous to life or property.
9. No change in the character of occupancy or use of a building or structure shall be made without a Certificate of Occupancy. The Building Official may issue a Certificate of Occupancy without certifying that the building complies with all the provisions of these codes so long as he or she finds to do so will not endanger life.
10. All buildings or structures, both existing and new, and all parts thereof shall be maintained in a safe and sanitary condition. All devices or safeguards, which are required by the construction codes in a building or structure when erected, altered, or repaired, shall be maintained in a good working order. The owner or the owner’s designated agent shall be responsible for the maintenance of buildings and structures.
11. Any building or structure, including mobile homes, and factory built homes moved into or relocated on existing parcels or to a new parcel within those areas of San Mateo County within the jurisdiction of the Building Official shall meet standards required by this code for new buildings or structures. Permits for manufactured homes may be denied if more than ten (10) years has elapsed between the date of manufacture and the date of application for a permit to install the manufactured home.

San Mateo County, Cal., Building Regulations [2014] ch.2, art.2 § 9022. Existing Buildings.